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The upper, darker moth is a female Euxoa lidia locked in copulation with a male Xestia c-nigrum. They were in a mercury vapour light-trap 16 km E of Invermere, B.C., in July 1994. The photograph was digitized on an Abaton page scanner at 300 dots per inch and, for the first time, sent elec- tronically to the Graphic Designer by the Editor. He solicits good quality line drawings or pho- tographs for future insects of the year. The Journal of the Entomological Society of British Columbia is published annually in December by the Society Copyright © 1994 by the Entomological Society of British Columbia Designed and typeset by UVic Graphics and printed by Printing & Duplicating Services, University of Victoria, Victoria, B.C., Canada. Text printed on 60 Ib. Halopaque Vellum Recycled Paper. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 1 Journal of the Entomological Society of British Columbia Volume 91 Issued December 1994 ISSN #007 1-0733 Directors of the Entomological Society of British Columbia, 1994~-95........... 0.0.2.0... 22 eee 2 Gillespie, David R. and D.J.M. Quiring. Reproduction and longevity of the predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae) and its prey, Tetranychus urticae (Acan: etranychidac) on different host plants. ........c00c00s08 bee gee eeecsennsaseeegceeds | B) Schaber, Burton D., Timothy J. Lysyk and Derek J. Lactin. Phenology of the alfalfa weevil . (Coleoptera: Curculionidae) in alfalfa grown for seed in southern Alberta .................... 9 Cannings, Robert A. Robber flies (Diptera: Asilidae) new to Canada, British Columbia, Yukon and the Northwest Territories with notes on distribution and habitat.................... 19 Knight, Alan. Insect pest and natural enemy populations in paired organic and conventional appie orchards in the Yakima Valley, Washington .......3...0..600c00eessececdscccessenceces 27 Taylor, S.P. and R.D. Cozens. Limiting white pine weevil attacks by side and overstory shade inate TINGE CaCONve-FOTESt REGION Geag o5 cian send ow alee ska 6 moa bea bane ha ccllnw 4 ee Giwoe® aie 37 Mayer, D.E. Effects of male to female ratio and number of females per nesting tunnel on sex ratio and number of progeny of the alfalfa leafcutter bee Megachile rotundata Cavimemoprera: Wie CaChNidae) 6.6 ooo) nein c Boma de dak chase Shans we Gd Ge wage wend eeee nares 43 Cossentine, J.-E. and L.B. Jensen. The role of two eulophid parasitoids in populations of the leafminer, Phyllonorycter mespilella (Lepidoptera:Gracillariidae) in British Columbia ......... 47 Syed, A. Notes on the biology and rearing of the carrion fly Prochyliza brevicornis (Melander) MD ate rae OP MING AC)», rs og en peor vegies reese we Se ng Soe Mw aU Fp cneeas laure aes ere ote 3D Wood, L., D.A. Raworth, and M. Mackauer. Biological control of the two-spotted spider mite in raspberries with the predator mite, Phytoseiulus persimilis ......... 00. c ccc ee eee e eee eens Die Bradley, S.J. and D.F. Mayer. Evaluation of monitoring methods for western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), during the blossom period of BGT ATA eS MINEO AIO LE Se aa 4c eed ts cca Prats Cate Sai) ase i a Sa Mw a ae ee ee ee eee oe 63 NOTES Naumann, Ken. An occurrence of two exotic ants (Formicidae) species in British Columbia ........ 69 Blatt, S.E. An unusually large aggregation of the western conifer seed bug, Leptoglossus occidentalis (Hemiptera: Coreidae), in a man-made structure ................... 71 Fitzpatrick, Sheila M., James T. Troubridge, and Celine Maurice. Parasitoids of blackheaded fireworm (Rhopobota naevana Hbn.) larvae on cranberries, and larval escape behaviour ........ a5) IO UICE NWO: CON TRIBU TORS «re cns s cicaise vce go piven oes che enn edieens asus $4 une cose eeeme Je. op) J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 DIRECTORS OF THE ENTOMOLOGICAL SOCIETY OF BRITISH COLUMBIA FOR 1994-95 President Linda Gilkeson B.C. Ministry of Environment, Victoria President-Elect Gail Anderson Simon Fraser University Past-President Sheila Fitzpatrick Agriculture Canada, Vancouver Secretary Robb Bennett Ministry of Forests, 7380 Puckle Rd., R.R.#3, Saanichton, B.C. V8M 1W4 Treasurer Shiyou Li Agriculture Canada, Vancouver Editorial Committee (Journal) Peter Belton (Editor) H.R.MacCarthy Dave Raworth Editor (Boreus) E.M. Belton S.E.U. Directors K. Naumann (2nd) _L. Poirier (2nd) D. Morewood (1st) H. Philip (1st) M. Smirle (ist) Honorary Auditor Terry Shore Pacific Forestry Centre, Victoria Regional Director of National Society Terry Shore J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 3 Reproduction and longevity of the predatory mite, Phytoseiulus persimilis (Acari: Phytoseiidae) and its prey, Tetranychus urticae (Acari: Tetranychidae) on different host plants’ DAVID R. GILLESPIE and D.J.M. QUIRING PACIFIC AGRICULTURE RESEARCH CENTRE, AGRICULTURE AND AGRIFOOD CANADA, P.O. BOX 1000, AGASSIZ, B.C. VOM 1A0 ABSTRACT The biological control of twospotted spider mites by the predator Phytoseiulus persimilis is usually unsuccessful on greenhouse tomato crops in British Columbia. Experiments were con- ducted to determine the influence of host plant on the longevity and reproduction of the preda- tor, and on the suitability of twospotted spider mites as prey. Lifespan and reproduction of P. persimilis were lower on tomato leaves than on bean leaves but feeding on spider mites that had been reared on tomato or bean leaves had no effect on the reproduction or lifespan of P. per- similis. A strain of twospotted spider mites that came from an outbreak on a greenhouse tomato crop lived for shorter periods and laid fewer eggs when confined on tomato leaves than on bean leaves. A strain of twospotted spider mites that had been maintained on bean leaves was unable to reproduce on tomato leaves. Exudates from glandular hairs were toxic to P. persimilis. Glan- dular hairs are important in pest management on tomato crops. Their removal through breeding might make plants more susceptible to herbivores. Therefore it would be preferable to develop other methods for biological control of twospotted spider mites on tomato. INTRODUCTION Biological control of twospotted spider mites, Tetranychus urticae Koch (Acari: Tetranychi- dae) by Phytoseiulus persimilis (Dosse and Bravenboer (Acari: Phytoseiidae) is successful on wide range of greenhouse crops throughout the world (van Lenteren and Woets 1988). How- ever, the use of this predator for biological control of T. urticae on greenhouse tomato crops has been unsuccessful in British Columbia, and elsewhere (Ravensburg et al. 1982). This has been attributed to the entrapment of P. persimilis on the glandular hairs on the stems and leaf petioles of tomato plants (van Haren et al. 1987). It is possible that other factors associated with hairiness may also be involved in the lack of efficacy of P. persimilis on greenhouse tomato crops. Many mechanisms of resistance to insects and mites have been identified in tomato (Farrar and Kennedy 1991b). Several toxic and repel- lant chemicals, for example 2-tridecanone, are present in the glandular hairs and on the leaves of tomato plants (Farrar and Kennedy 1991b). A predator such as P. persimilis would be ex- posed to these chemicals either directly, through contact with the leaf, or indirectly, through in- gestion of prey. Many of the mechanisms of resistance in tomato are effective against 7: urticae (Farrar and Kennedy 1991b). The degree to which the tomato plant affects reproduction and population growth in spider mite populations might aid in determining strategies for dealing with this pest. We present here results of experiments to determine the mortality and fecundity of the preda- tory mite, P. persimilis and its prey, T. urticae, on tomato leaves. MATERIALS AND METHODS General: The spider mite strains used in this study were maintained in continuous culture on their respective host plants. The strain adapted to feeding on bean (B-strain) originated from a commercial insectary (Applied Bio-nomics Ltd., Sidney, B.C.) where it had been reared con- tinuously on snap bean (Phaseolus vulgaris L.) for several years. The strain adapted to feeding on tomato (Lycopersicon esculentum Mill.) (T-strain) originated from an outbreak on tomato plants in a greenhouse in Surrey, B.C. in 1992. The B-strain mites were reared on pinto beans (P. vulgaris) in pots on a laboratory bench. The 4 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 plants were inoculated weekly from stock materials obtained from Applied Bio-nomics Ltd. The T-strain mites were reared on excised tomato leaflets (cv Dombito, DeRuiter Seeds, Ohio) on styrofoam trays floating in water filled trays. The petioles of the leaflets were inserted through holes in the styrofoam into the water below. Fresh leaves were added to the trays as required. The P. persimilis used in these experiments were also obtained from Applied Bio-nomics. Eggs of P. persimilis were produced for experiments by isolating 2 to 5 females on detached bean leaves on water-saturated cotton batting and providing them with abundant spider mites. The predator eggs were removed every 24 h. Females of P. persimilis were produced for ex- periments by rearing single eggs to adults on detached bean leaves with an abundant supply of spider mites (B-strain). The predators were examined daily, and the females were used in ex- periments within 24 h of the final molt to adult. All experiments were conducted in growth chambers at 26°C under 16h of light from cool white fluorescent tubes. Twospotted spider mites: The effects of host plant species and spider mite strain on egg hatch, development, and survival to adult of T: urticae were determined on leaf discs on water- saturated cotton in petri dishes. Eight discs, 1 cm in diam., of each plant species were placed in rows of four on water-saturated cotton batting in each of ten, 9.2 cm square, plastic Petri plates. A single spider mite egg (< 24h old) was placed on each leaf disc. Four bean leaf discs in each plate received B-strain mite eggs, and four received T-strain mite eggs. Four tomato leaf discs received T-strain mite eggs and four received B-strain eggs. The spider mites were ob- served daily through their development. Molts were determined by the presence of cast skins. Spider mites were moved to fresh leaf discs as required. The effects of the plant host on reproduction in the two strains of spider mite were determined in an identical experimental design to that above, except that adult females (<24 h old) were placed on leaf discs. These females were obtained by rearing spider mites individually on their respective host plants from the protonymph stage. Females at the quiescent deutonymph stage were confined with males. On molting to adult, both the female and the male were transferred to either bean or tomato leaf discs in the experiment. Eggs were counted and removed daily. The mites were transferred to fresh leaf discs as required. Results were analyzed as a factorial design by analysis of variance (Proc GLM, SAS Institute 1992). Predator mites: To determine if plant species affected reproduction of P. persimilis, a single female (<24 h old) was placed with a male on either a bean leaf disc infested with B-strain spi- der mites or on a tomato leaf disc infested with T-strain spider mites. Predator eggs were counted daily. Predators were transferred to fresh leaf discs as required. The results were analyzed by T- test. Development time of P. persimilis fed on the two different strains was determined on 2 cm diam. plastic discs floating on water-saturated cotton batting in a Petri dish. Four discs were placed in each Petri dish and a single egg of P. persimilis was placed on each disc. After the eggs hatched, two of the predators were fed eggs of spider mites reared on bean plants, and two were fed eggs of spider mites reared on tomato plants. Eggs were collected with a camel-hair brush from active spider mite colonies. An excess supply of eggs was placed on each disc. Molts were determined by the presence of cast skin. The results were analyzed by T-test. To determine if the effects seen in the previous experiment were due to plant species or spi- der mite strain, adult female P. persimilis (<24h old) were placed on styrofoam discs 2.5 cm in diam. Mixed age populations of spider mites were provided daily on fresh pieces of leaf. The prey were either B-strain spider mites on a bean leaf, B-strain mites on a tomato leaf, T-strain mites on a tomato leaf, or T-strain mites on a bean leaf. Predator eggs were counted and removed daily. Only records for those females that died of natural causes on the disc surface were used for analysis. Mites that abandoned the discs and drowned were not included in the analysis. Re- sults were analyzed by a factorial design analysis of variance (Proc GLM, SAS Institute, 1992). The toxicity of exudates from glandular hairs of tomato to P. persimilis females was deter- mined by exposing them directly to glandular hairs, or to an aqueous solution of exudates, or to water. Twenty mites were exposed directly to glandular hairs. These were held on the tip of a moist camel-hair brush and lightly touched to 30 to 40 glandular hairs on a piece of tomato stem. They were then placed on a sheet of filter paper to recover, then held for examination. Twenty J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 5 mites, selected at random, were exposed to exudate solution. These were dipped for 4 sec in the solution, placed on filter paper to dry, and then held for examination. The solution was prepared by collecting exudate from the tips of glandular hairs, allowing this to dry overnight, then dis- solving 0.28¢ of the dried exudate in 2 ml of distilled, de-ionized water. Twenty mites were sim- ilarly dipped in distilled, de-ionized water. After 24 h, the dead mites were counted. Results were analyzed by a x2 test for goodness of fit. RESULTS Twospotted spider mites: Neither host plant nor mite strain had a significant effect (p>0.05) on the proportion of eggs hatching (Table 1). There was a significant interaction (F=18.11, p>0.001) between host plant and mite strain with respect to survival of mites from hatch to adult. There was high mortality of B-strain spider mites on tomato leaf discs, but not on bean leaf discs, and low mortality of tomato strain spider mites on both tomato and bean. Due to high mortality of B-strain mites on tomato leaf discs data on development of this strain were not in- cluded in the analysis. Instead, host plant/mite-strain combinations were used as three treat- ments in a two-way analysis of variance with sex of the mite as the other main effect. There was no interaction between sex of mite and treatment (p>0.05). Neither sex of the egg nor host- plant/mite-strain combination had an effect on the time to egg hatch (p>0.05; Table 2). Female mites took longer to develop from larvae to adults than males (F=4.71, p=0.0331). Treatment Table 1 Mean number of eggs hatched, and survival to adult in 10 cohorts of 4 mites of each strain on bean and tomato leaf discs. Host plant Mite strain Number hatched of four (N=10) — Proportion surviving of four (N=10) Bean Bean 3.6 0.90 Tomato epg | 0.85 Tomato Bean 3.4 0.03 Tomato ie 0.88 Mean Square Error 0.3167 0.1721 Anova Results Host plant F (p) 1.26 (0.2685) 15.42 (0.0004) Mite strain F (p) 0.32 (0.5776) 13.37 (0.0008) Host x Strain F (p) 0.00 (1.000) 18.11 (0.0001) Table 2 Mean (N, Standard Error) number of days for tomato and bean strain spider mites to complete develop- ment on tomato and bean leaf discs. Host plant — Mite strain Male Female Egg Total* Egg Total* Tomato Tomato aa 10.0a 5.0a 11.2a (7, 0.18) (7, 0.90) (19, 0) (19, 0.46) Bean Tomato 5.2a 5.2b 5.3a 5.7b (9, 0.15) (9, 0.36) (18, 0.11) (18, 0.27) Bean Bean Sl Ds 1b 5.2a 5.6b (19, 0.11) (19, 0.19) (10, 0.20) (10, 0.16) * Time from egg hatch to molt to adult Means in a column followed by the same letter are not significantly different. 6 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Table 3 Egg production and survival of bean strain and tomato strain adult female twospotted spider mites on bean and tomato leaf discs. Host plant Mite strain N Number of Eggs Days Alive Bean Bean 9 49.7 13.2 Tomato 15 38.7 16.6 Tomato Bean 10 0.6 6.0 Tomato 8 2.6 10.0 Mean Square Error 27.8203 7.4501 Anova Results Host plant F (p) 22.75 (0.0001) 8.55 (0.0058) Mite strain F (p) 0.26 (0.6124) 2.43 (0.1270) Host x strain F (p) 0.55 (0.4637) 0.02 (0.8960) Table 4 Mean development and reproduction parameters (+ standard error) for Phytoseiulus persimilis feeding on spider mites on bean or tomato leaves (N = 10). Host plant: Bean Tomato Development Time 2.6+0.18 2.840.17 Total Eggs Laid 56.0+£5.67 38.143.34* Days of Oviposition 13.9+1.50 9.6+0.87* Lifespan 2072274 11.3+0.60* Eggs laid per day 3.0+0.46 3.4+0.28 *Significant effect of host plant (T-test, p<0.05) (host-plant/mite-strain combination) had a significant effect on the time for development from egg to adult (F=134.96; p<0.0001). Both male and female T-strain mites required significantly longer to develop on tomato than either T-strain mites on bean or B-strain mites on bean. Spider mites produced significantly fewer eggs on leaf discs of tomato than they did on leaf discs of bean (Table 3). Spider mite lifespan was also shorter on leaf discs of tomato than on leaf discs of bean. Strain had no effect on either egg production or longevity of spider mites. Predator mites: There was no effect of spider mite (prey) strain on development time of P. persimilis on leaf discs (Table 4). Females on discs of tomato leaf laid fewer eggs over a shorter period and had shorter lives than females on discs of bean leaf (Table 4). There was no effect of host plant species on the rate of oviposition. | When P. persimilis were confined on styrofoam discs and supplied with prey on leaf pieces, there was no effect of host plant leaf pieces on the life span or fecundity of female P. persimilis (Table 5). Females that were fed B-strain mites lived for a significantly shorter time than females that were fed T-strain mites irrespective of the plant species on which the spider mites were pre- sented. Ten percent of females of P. persimilis died after exposure to water, 50% died after exposure to a solution a glandular hair exudates, and 85% died after direct contact with glandular hairs. These were significant differences (y2=22.6, p<0.05). DISCUSSION The twospotted spider mite, T: urticae, is broadly polyphagous. However, some spider mite populations are selectively adapted to only some of the plants that are part of their host range (Fry 1989). It is probable that no spider mite population is able to feed and reproduce on all of J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 7 the known hosts. The T-strain of spider mites used in this study originated from an outbreak on a tomato crop in a commercial greenhouse. However, it was able to use bean, P. vulgaris, as a host, and survived and reproduced better on bean than on tomato (Table 3). There were no dif- ferences in reproduction or survival between the B- strain and the T-strain on bean. On tomato, the B-strain of 7: urticae was virtually unable to reproduce. Very few immatures survived to re- produce, and females placed on tomato laid few eggs. The reproductive abilities of the T-strain of T-urticae are so reduced on tomato that it appeared surprising that this strain was able to survive on tomato, let alone generate an outbreak. However, in laboratory culture this strain reproduced rapidly on excised leaves of tomato. The major dif- ference between the laboratory culture and the experiments described here was that many spider mites were used to start a culture, whereas a single mite was used in experiments. The large num- ber of mites used to inoculate the laboratory colony produced copious silk. Mites tend to walk on the silk and would therefore have been isolated from the leaf surface. Tomato plant glandular hairs contain many substances that are toxic to twospotted spider mites (Farrar and Kennedy 1991b). The silk would tend to protect the mites from the effects of the hairs and the larger num- ber of mites on the leaf would tend to dilute exposure to glandular hair substances. The strain of spider mite had no effect on the fecundity of the predator, P. persimilis. In an ini- tial experiment (Table 4) fecundity was lower for females feeding on T-strain spider mites on tomato leaves than for those feeding on B-strain spider mites on bean leaves. On styrofoam discs, neither the strain of spider mites nor the plant species on which they were provided had any significant effect on reproduction in the predator. This is probably because the predators did not have to spend all of their time on the plant section provided, but could move about on the styrofoam disc, thus avoiding contact with the glandular hairs. Predators that were fed on B-strain spider mites had shorter lives than predators fed on the T- strain mites (Table 5). In these results the interaction between host plant and spider mite strain was not significant. However, it is large enough to indicate that the significant effect of spider mite strain on lifespan could have resulted from the short lifespan (15.3 days) of P. persimilis that were fed B-strain spider mites on tomato leaf pieces. Lifespan of P. persimilis in all other treatments was greater than 18 days. Mortality among B-strain mites on tomato leaves could have reduced the number of prey available to P. persimilis. Plant resistance characters are known to affect the biology of natural enemies, even though Wheatley and Boethel (1992) showed that resistance to spider mites in soybeans (Glycine max) had no effect on P. persimilis. However, other natural enemy associations are affected by resistance characteristics in soy- beans (Orr and Boethel 1986, Rogers and Sullivan 1986, Yanes and Boethel 1983). Resistance to Manduca spp. (Lepidoptera: Sphingidae) in tomato has toxic effects on the parasitoid Te- lenomus sphingis (Hymenoptera: Scelionidae) (Farrar and Kennedy 1991a). Table 5 Numbers of eggs laid and lifespan for Phytoseiulus persimilis females held on styrofoam floating discs and fed spider mites reared on either bean or tomato leaves (N = 10). Host plant Mite strain Total Eggs Lifespan (days) Eggs per day Bean Bean 53:1 18.1 32 Tomato 54.9 18.9 3.1 Tomato Bean 44.2 133 3.0 Tomato 42.6 19.9 2.4 Mean Square Error 23.95 3.9 L538 Anova Results Host Plant F (p) 1.96 (0.1701) 0.51 (0.4801) 0.98 (0.3283) Mite Strain F(p) 0.00 ( .9895) 4.58 (0.0392) 0.53 (0.4714) Host x Strain F (p) 0.05 (0.8236) 2.27 (0.1407) 0.37 (0.5475) 8 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 The host plant of the spider mite upon which P. persimilis fed did not greatly affect the biol- ogy of the predator. Females of P. persimilis confined on tomato leaflets have a shorter lifespan than females confined on bean leaves. As a consequence, the number of eggs laid is reduced, and population growth and predation would be reduced. This effect is due to contact with leaf, not the consumption of prey. Eating B-strain mites fed on tomato reduced the lifespan of P. per- similis. The cause of this was not clear. Up to 75% of P. persimilis die moving from leaf to leaf on tomato plants (van Haren et al. 1987). If the reproduction of the remainder is reduced by up to 40% as a result of reduced life- span on leaf blades, then it would appear that enormous numbers of predators would have to be introduced into tomato crops to offset these effects Resistance in tomato plants to spider mites can be affected to some degree by environmental factors. Increased fertilization reduces resistance through lowering both glandular hair densities and 2-tridecanone levels (Barbour et al. 1991). Glandular hair density is conversely increased in long-day, high light level conditions (Kennedy et al. 1981). Glandular hair density and other resistance factors might be reduced through breeding. However, resistance to pests based on glandular hairs is important for preventing feeding by many species of herbivores (Farrar and Kennedy 1991b), and should not be discarded for the sake of single predator/prey association. It would be preferable to develop alternative strategies for releasing and managing P. persimilis in tomato crops, or to seek other predator species that are not affected by the resistance mecha- nisms of tomato. ACKNOWLEDGEMENTS We thank J. Treurneit for technical assistance on parts of the project, and Applied Bio-nomics Ltd., Sidney, B.C., Canada for the supply of spider mites and predators. NOTE 1. Contribution number 516 from the Pacific Agriculture Research Centre, Agassiz, B.C. REFERENCES Barbour, J.D., R.R. Farrar Jr. and G.G. Kennedy. 1991. Interaction of fertilizer regime with host-plant resistance in tomato. Entomol. exp. appl. 60: 289-300. Farrar, R.R. Jr. and G. Kennedy. 1991a. Inhibition of Telenomus sphingis an egg parasitoid of Manduca spp. by tri- chome/2-tridecanone-based host plant resistance in tomato. Entomol. exp. appl. 60: 157-166. Farrar, R.R. Jr. and G. Kennedy. 1991b. Insect and mite resistance in tomato pp.121-142 Jn Kaloo, G. (ed.) Genetic im- provement in tomato. Springer-Verlag. Berlin, West Germany. Monographs on Theoretical and Applied Genetics. Fry, J.D. 1989. Variation among populations of the twospotted spider mite, Tetranychus urticae Koch (Acari: Tetrany- chidae), in measures of fitness and host-acceptance behavior on tomato. Environ. Entomol. 17: 287-292. Haren, R.J.F. van, M.M. Steenuis, M.W. Sabelis, and O.M.B. De Ponti. 1987. Tomato stem trichomes and dispersal suc- cess of Phytoseiulus persimilis relative to its prey, Tetranychus urticae. Exp. Appl. Acarol. 3: 115-121. Kennedy, G.G., R.T. Yamamoto, M.B. Dimock, W.G. Williams and J. Bordner. 1981. Effect of daylength and light in- tensity on 2-tridecanone levels and resistance in Lycopersicon hirsutum f. glabratum to Manduca sexta. J. Chem. Ecol. 7: 707-716. Lenteren, J.C. van, and J. Woets. 1988. Biological and integrated pest control in greenhouses. Annu. Rev. Entomol. 33: 239-269. Orr, D.B. and D.J. Boethel. 1986. Influence of plant antibiosis through four trophic levels. Oecologia 70: 242-249. Ravensburg, W.J., J.C. van Lenteren and J. Woets. 1982. Developments in application of biological control in greenhouse vegetables in the Netherlands since 1970. International Organization for Biological Control, West Palearctic Regional Section Bulletin VI/3: 36-48. Rogers, D.J. and M.J. Sullivan. 1986. Nymphal performance of Geocoris punctipes (Hemiptera: Lygaeidae) on pest-re- sistant soybeans. Environ. Entomol. 15: 1032-1036. SAS Institute Inc. 1992. SAS/STAT users guide. Version 6, Fourth Edition, Volume 1, Cary, NC: SAS Institute Inc. 1992. 943 pp. Wheatley, J.C. and D.J. Boethel. 1992. Populations of Phytoseiulus persimilis (Acari: Phytoseiidae) and its host, Tetrany- chus urticae (Acari: Tetranychidae), on resistant and susceptible soybean cultivars. J. Econ. Entomol. 85: 731-738. Yanes, J. Jr.and D.j. Boethel 1983. Effect of a resistant soybean genotype on the development of the soybean looper (Lep- idoptera: Noctuidae) and an introduced parasitoid, Microplitus demolitor Wilkinson (Hymenoptera: Braconidae). Environ. Entomol. 12: 1270-1274. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 9 Phenology of the alfalfa weevil (Coleoptera: Curculionidae) in alfalfa grown for seed in southern Alberta BURTON D. SCHABER, TIMOTHY J. LYSYK and DEREK J. LACTIN AGRICULTURE AND AGRI-FOOD CANADA RESEARCH CENTRE, P. O. BOX 3000, MAIN LETHBRIDGE, ALBERTA, CANADA T1J 4B1 ABSTRACT An algorithm to forecast occurrence of four life-stage categories of the alfalfa weevil, Hypera postica (Gyllenhal), was derived from data collected in fields of seed alfalfa, Medicago sativa (L.) in southern Alberta. The algorithm assumes a linear developmental response to mean daily temperatures above a threshold of 10°C. Overwintering adults were active after the accumula- tion of 100 degree-days above 10°C (DDj9), and were scarce by 250-300 DDjo. Early larvae (instars 1 + 2) were found beginning at 120 DDj9 and their numbers peaked at 200 DD} 0. Late larvae (instars 3 + 4) were present beginning at 160 DDjo and their numbers peaked at 350 DD)j0. New generation adults appeared after 500 DDjo. In southern Alberta, alfalfa seed pro- duction is frequently combined with honey production. This algorithm enables producers to forecast the occurrence of the most damaging stage of alfalfa weevils which may require con- trol with insecticides; the advance notice enables optimal timing of treatment and also allows apiarists to minimize pesticide mortality by moving or confining their bees. Key words: Thermal units, degree days, simulation, phenology INTRODUCTION Pest control measures are economically justifiable only if their benefits exceed their cost (Stern et al. 1959). Normally, cost is the sum of pesticide purchase plus its application, and benefit is measured by reduced yield loss. However, other factors may enter the cost:benefit equation; this occurs in alfalfa production in southern Alberta, where seed producers frequently obtain additional income by charging apiarists to place honeybees (Apis mellifera L. (Hy- menoptera: Apidae)) in their fields. Thus, strategies to control pest insects in alfalfa seed fields must acknowledge the susceptibility of honeybees to many pesticides. One approach to reconciling alfalfa pest management with apiculture is to give apiarists suf- ficient warning to cover the hives, or to move them, before pesticides are applied. This approach requires a method of forecasting the occurrence of the pest population. This paper presents a simple method of doing so, which is based on observed correlations between phenological events and degree-day accumulations. In southern Alberta, the alfalfa weevil is a serious insect pest of alfalfa, feeding on shoots, flower buds and foliage during prebloom to early bloom (Hamlin et al. 1949). If not controlled it can severely reduce seed yield. Adult alfalfa weevils spend the winter in protected locations in alfalfa fields or in litter nearby. Overwintered adults become active about the time the first alf- alfa shoots appear in the spring. They feed for a few days, mate, and begin ovipositing. Peak egg density usually occurs in late May or early June, but eggs can be found during most of the sum- mer. Rates of pre-imaginal development are temperature-dependent. Egg incubation takes 4 to 21 days. Larvae develop through the four instars in about 3 to 4 weeks. Instars 1 and 2 (early lar- vae) feed within the tightly-curled developing leaves and buds; instars 3 and 4 (late larvae) feed on expanded leaves. Feeding damage is most obvious in mid- to late-June, concurrent with peak densities of late larvae. Defoliation is most severe toward the terminals. This type of feeding results in loss of foliage, flower buds, and nutrients, with consequent delays in plant growth and development. Quantity and quality of the seed yield may be reduced. Late larvae inflict the greatest damage, so agricultural losses can be expected to start accu- mulating at the onset of this life stage (Dennis et al. 1986). Consequently, the timing of control tactics for the alfalfa weevil should be optimized, based on an understanding of physiological 10 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Proportion of population in life stage Figure 1. Observed and predicted proportion of alfalfa weevil in relation to DD 9. a) Over- wintering adults (life stage = 1): o and solid line. New generation adults (life stage = 4) A and dotted line; b) first and second instars (early larvae; life stage = 2); c) third and fourth instars (late larvae; life stage = 3). Lines are predictions made using Equations 1-3 in text. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 1] and behavioral processes (Harcourt 1981; Whitford and Quisenberry 1990), to target this life stage. This optimization requires information on the seasonal abundance and time of occurrence of the immature stages of the alfalfa weevil through a combination of population monitoring and phenological models (Schaber and Richards 1979). In southern Alberta, chemical insecticides are the primary method of alfalfa weevil control. Efficient use of insecticides requires that applications should be timed to target the first late lar- vae, 1.e. after they have moved to exposed positions on the leaves, but before they have caused much damage. This timing requirement establishes a potential conflict between pest control and honey production. A reliable method of forecasting the occurrence of late larvae could re- solve this conflict. This study was conducted to develop a technique that would predict the appearance of late instar alfalfa weevil larvae in seed alfalfa fields, using southern Alberta field data. This tech- nique would enable better timing of insecticide applications in relation to insect development, and allow seed producers and apiarists more lead time to protect pollinators. The temperature-dependence of insect development dictates that developmental models be based on thermal-unit accumulation. Simple methods for modelling phenology based on field data are available, and can be used to develop realistic models in the absence of detailed data on insect development processes (Hudes and Shoemaker 1988; Kemp and Onsager 1986; Kemp et al. 1986; Lysyk 1989). Degree-day accumulation has been used to predict peak hatch and sub- sequent activity of alfalfa weevil in forage alfalfa in southern Ontario (Harcourt 1981). How- ever, Tauber et al. (1988) have suggested that the phenology of an insect species can vary among geographic regions due to adaptation of thermal biology to local climatic conditions, so another objective was to compare phenology of the alfalfa weevil populations in southern Ontario and southern Alberta. METHODS Algorithm development The algorithm was developed using phenology data obtained from four research plots at the Agriculture and Agri-Food Canada Research Centre (AACRC) at Lethbridge, Alberta. Alfalfa weevil abundance was determined by taking five sweeps per plot with a 38-cm net (Johansen et al. 1979). Each plot was sampled every one to three days from 3 June to 12 August 1985; 12 May to 8 August 1987; 3 June to 20 July 1988; 3 June to 4 July 1989, and was sampled weekly from 4 June to 23 July 1990. Daily maximum and minimum temperatures (°C) were ob- tained from the AACRC meteorological station. Alfalfa weevil phenology was modeled by correlating phenological events with degree-day accumulations using a developmental threshold of 10°C. This threshold was used because, al- though alfalfa weevil eggs hatch at 8°C, the resulting larvae do not survive even if subsequently exposed to a higher temperature (Guppy and Mukerji, 1974). Accumulated degree-days above 10°C (DDj0) from 1 January were calculated for each year by sine-wave integration (Allen 1976). Accumulated DD) on each date was rounded to the nearest 10, and samples from the 4 plots were grouped according to these rounded values. The proportion of alfalfa weevils which were adults, early larvae and late larvae were calculated for all such grouped samples, and these proportions were related to the rounded DD 9 accumulations by non-linear regression (Proc NLIN, SAS Institute 1989) as outlined below. To provide a standardized estimate of when the weevils and larvae were most abundant, and to establish correlations between phenological events and DD;9 accumulations, their relative abundance was calculated for each plot on each day in each growing season by summing the number of weevils collected and dividing by the greatest number collected in one day for that plot in that year. These relative abundances were grouped across plots and years by the rounded degree-day values. The correlations between relative abundance and DD 9 accumulations were used to develop an algorithm to predict the appearance of the different life stages. Alfalfa weevil phenology was divided into four stages (i): overwintered adults (i = 1), i.e., 12 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Proportion of population in life stage | or greater 0 0.2 0.4 0.6 0.8 1.0 ae (DD, 0" DD min ) (DDmax- DDmin ) Figure 2. Proportion of alfalfa weevil in a) life stage 2 or greater, b) life stage 3 or greater, and C) life stage 4. Solid lines are model predictions using equation 2 and parameters estimates given in Table 1. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 13 those present before the larval peak at 350 DD} ; early larvae (i = 2); late larvae (i = 3); and new generation adults (i = 4), i.e, those occurring after the larval peak at 350 DD jo. The algorithm was developed as outlined below (Hudes and Shoemaker 1988). For each rounded DD jo value, the following calculations were made: Fy = (nj +3 +ng)/2n F3 =(n3+ng)/2n F4y=ng/ =n where nj;(i=2-4) is the number of weevils in life stage i, Xn is the total number of weevils, and F; is the proportion of insects in life stage i or later. Note that because all insects are in a life stage equal or greater than the overwintered adult stage, F) = 1. The time trends in each F; were modelled using equation 1. Fe=(1-0-4inppi (1) Non-linear regression was used to obtain estimates of the parameters (aj, bj; 1 = 2 - 4). The variable t; is a scaled estimate of thermal time calculated for each life stage as: pe DD 9 - DD mini (2) DD maxi) - PP minci In equation 2, DD ynin(i) and DD max(i) represent the approximate value of DDjo for the be- ginning and end of life stage 1, obtained by inspection of the data. The functions describing time-change in ; were then used to predict the proportion of insects in each life stage (fj): ! 1 25 Ss (3) T> WD WD WD WwW i) Il ll ees W dN ' ‘ er) 7a) ey £ ll a8 a Algorithm validation Independently-obtained data were used to validate the algorithm. These were collected from plots in Brooks, Rosemary and Rolling Hills, Alberta (ca. 130 km N.E. of Lethbridge) by WestAg, Inc., a pest management scouting company. These plots were sampled weekly for up to 13 weeks in 1984-1988, starting the last week of May and continuing through August. Samples in a specific plot in each year were taken at approximately the same time of day to min- imize any effects of insect diurnal cycle on sampling efficiency (Johansen et al. 1979). The data consisted of weekly mean numbers of adults and of early and late larvae. The numbers of fields sampled were 48, 40, 42, 48 and 42 for 1984 through 1988. Sample counts were tabulated weekly. Daily maximum and minimum temperatures were obtained for each year from the Alberta Special Crops and Horticultural Research Center in Brooks, Alberta, and the DD jo accumulation from January | were calculated by sine-wave integration (Allen 1976). The DDjo accumulation in the middle of each week was matched with the weekly insect data. The aver- age proportion of weevils in the adult, early larval, and late larval stages was calculated for each week and compared graphically to the algorithm predictions. 14 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Proportion of population in life stage i or greater 0 200 400 600 800 1000 Figure 3. Proportion of alfalfa weevil in commercial seed alfalfa fields. Symbols are observed mean proportion + | standard error, and lines are predictions made using Equations 1-3. a) adults, solid line is overwintered generation (life stage = 1) and dotted line is new generation (life stage = 4); b) first and second instars (early larvae; life stage = 2); c) third and fourth instars (late larvae; life stage = 3). J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 15 RESULTS Seasonal phenology of alfalfa weevil Adult weevils were first found at about 100 DD jo (Fig. 1a) and at that time were the only stage collected. The proportion of adult weevils declined from about 250 DD} and they had be- come scarce by 350 DD jo. Early larvae appeared at about 120 DD) (Fig. 1b), reached a max- imum at about 200 DD), and then declined slowly. Late larvae appeared at ca. 160 DD jo (Fig. 1c), peaked near 450 DD}, and then declined. New generation adult weevils began to appear after 400 DD jo, and increased steadily to nearly 100% of the population by 900 DD jo. Algorithm output Figure 1a-c illustrates the good agreeement between the algorithm output and the Lethbridge data. Estimates of the regression parameters are listed in Table 1. Coefficients of determination (r2) were 0.97, 0.84, and 0.74 for life stages 2, 3 and 4 respectively. Model predictions of pro- portions of insects in life stage i or greater are overlaid with observations in Fig. 2a-c Algorithm validation Observed and predicted values of the proportion of weevils in each life stage for the test data are shown in Fig. 3 a-c. The predicted proportions of weevils in the adult life stages (1 and 4) seem reasonable (Fig. 3a). For early larvae, the algorithm predicted the timing of the peak population (Fig. 3b), and in general captured the seasonal population trends, but overall un- derestimated the proportion of weevils in this life stage. For late larvae (Fig. 3c) the algorithm predicted the start of the stage and captured the essence of the seasonal trends, but tended to overestimate the proportion of insects in this stage. DISCUSSION The phenology we observed differed from that recorded in Ontario (Harcourt 1981). In On- tario, most of the feeding damage occurred between 260 and 335 Degree-days base 9°C, whereas in this study, the damaging stage extended beyond 500 DD)o. These differences may reflect adaptation of the insect to a different cropping pattern, i.e. seed alfalfa vs forage alfalfa, or to a different climate. Harcourt’s (1981) model does not seem to apply to the Alberta popu- lation of alfalfa weevil. Table 1 Estimated parameters for component equations of the algorithm simulating alfalfa weevil population phenology. Equation (1)@ Equation (2)° Life Stage (i) a b r2 DDmin DDmax o2 18.15 11.01 0.97 120 400 3 4.84 1.00 0.84 160 800 = 5.05 29.81 0.74 200 900 a Nonlinear regressions of the temporal change in proportions of observed insects in life stage (i), using Fo=[1-e-arnipi b Scaled estimates of thermal time for life stage (i), calculated as: oo DD (i) - DD minci DD max) - PP minty Details are given in the text. 16 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Although qualitatively similar, there is some discrepancy between the predictions and the validation data. Several factors can affect the accuracy and reliability of the algorithm. First, separating alfalfa weevil larvae into life stages is somewhat subjective, particularly when dif- ferentiating between second and third instars, and variation among observers can affect the ac- curacy of sampling for pest insect populations (Shufran and Raney 1989). Another possible source of the discrepancies results from the differing ways in which sam- ples were handled. The alfalfa weevils and larvae captured in the sweep net at Lethbridge were placed in paper bags and stored at —40°C until counted, whereas in the validation data they were counted in the fieid immediately after capture. These differences in method, coupled with the subjective assignment to stages, could affect the performance of algorithm. Another possibility is that the use of degree-days may not be strictly applicable because it dis- regards both the nonlinearity of the developmental rate function (e.g. Lactin and Holliday 1993), and the ability of insects to control body temperature behaviourally (Huey and King-. solver 1989), and can not account for the effects of transient unfavourable conditions (Lactin 1992). Finally, insecticides were used in the commercial fields surveyed by WestAg, Inc., and dif- ferential mortality among the life stages may acount for the bias between algorithm predictions and field data. Early larvae feed mostly within the flower buds and are largely protected from contact insecticides, whereas late larvae feed on expanded foliage and are not (Johansen et al. 1979). These differences in exposure risk could bias the population structure of the validation fields, compared to that predicted by the algorithm, which was based on observations from in- secticide-free fields. CONCLUSION This paper outlines the development of an algorithm to predict the occurrence of damaging stages of the alfalfa weevil. Although there is a consistent bias in the estimate of proportion of these stages in the population, the algorithm estimates the timing of stages quite well, and can provide sufficient advance warning to optimize the timing of insecticide application, and thus allow apiarists to remove or confine their bees. ACKNOWLEDGMENTS The authors thank G. G. Dorchak and D. Gregory for their assistance throughout the project, and to R. A. Butts and J. R. Byers for critical reviews of the manuscript. This is contribution #3879232 of the Lethbridge Research Centre. REFERENCES Allen, J.C. 1976. A modified sine wave method for calculating degree-days. Environ. Entomol. 5: 388-396. Dennis, B., W. P. Kemp, and R. C. Beckwith. 1986. Stochastic model of insect phenology: estimation and testing. En- viron. Entomol. 15:540-546. Guppy, J.C. and M. K. Mukerji. 1974. Effects of temperature on development rate of the immature stages of the alfalfa weevil, Hypera postica (Coleoptera: Curculionidae). Can. Entomol. 106:93-100. Hamlin, J. C., FV. Lieberman, R. W. Bunn, W. C. McDuffie, R. C. Newton, and L. J. Jones. 1949. Field studies on the alfalfa weevil and its environment. U.S.D.A. Tech. Bull. 975. Harcourt, D. G. 1981. A thermal summation model for predicting seasonal occurrence of the alfalfa weevil, Hypera pos- tica (Coleoptera: Curculionidae), in southern Ontario. Can. Entomol. 113:601-605. Harcourt, D. G., J. C. Guppy, and M. R. Binns. 1977. The analysis of intrageneration change in eastern Ontario popu- lations of the alfalfa weevil, Hypera postica (Coleoptera: Curculionidae). Can. Entomol. 109:1521-1534. Hudes, E. S., and C. A. Shoemaker. 1988. Inferential method for modelling insect phenology and its application to the spruce budworm (Lepidoptera: Tortricidae). Environ. Entomol. 17:97-108. Huey, R.B. and J.G. Kingsolver. 1989. Evolution of thermal sensitivity of ectotherm performance. Trends in Ecology and Evolution 4: 131-135. Johansen, C., C. Baird, R. Bitner, G. Fisher, J. Undurraga, and R. Lauderdale. 1979. Alfalfa seed insect pest manage- ment. WREP 12. Cooperative Extension, Washington, Washington State University, Pullman, WA. Kemp, W. P., and J. A. Onsager. 1986. Rangeland grasshoppers (Orthoptera: Acrididae), modelling phenology of nat- ural populations of six species. Environ. Entomol. 15:924-930. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 17 Kemp, W. P., B. Dennis, and R. C. Beckwith. 1986. Stochastic phenology model for the western spruce budworm (Lep- idoptera: Tortricidae). Environ. Entomol. 15:547-554. Lactin, D. J. 1992. Thermal biology of the Colorado potato beetle (Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae)), with application to pest management decision making. Ph.D. thesis, University of Manitoba, 337 Pp. Lactin, D.J. and N.J. Holliday. 1992. 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COLUMBIA 91, DECEMBER, 1994 19 Robber flies (Diptera: Asilidae) new to Canada, British Columbia, Yukon and the Northwest Territories with notes on distribution and habitat ROBERT A. CANNINGS ROYAL BRITISH COLUMBIA MUSEUM, VICTORIA, B.C. V8V 1X4 ABSTRACT Twenty-one species of robber flies from British Columbia, not previously reported in Canada, are listed. Three genera are also new: Callinicus, Coleomyia, and Megaphorus. Two additional genera (Stichopogon and Andrenosoma) and 12 species already known from Canada are re- ported for the first time from British Columbia. Sixteen species new to the Yukon, and seven to the Northwest Territories are also recorded. These records update the list of Asilidae for this re- gion last published by Stone and others in 1965. Key words: Diptera, Asilidae, British Columbia, Yukon, Northwest Territories, distribution, status INTRODUCTION This paper makes some additions to the list of the robber flies (Diptera: Asilidae) of British Columbia, Yukon and western Northwest Territories and discusses the status of other species. Some of these new records represent recent collections, some are the result of the examination of unidentified or misidentified specimens in various collections, and some are records of ma- terial simply not previously published. The starting point for the list is the treatment of the Asil- idae by Martin and Wilcox in the Catalogue of Diptera of America by Stone et al. (1965). Species not listed from the region in that Catalogue, and that have not appeared in subsequent publications, are considered new records. Three short lists (Foxlee 1941, 1944; Hine 1904), overlooked and not in the 1965 Catalogue, are also included here as new material. Twenty-five species whose occurrences in the region have been published since the Catalogue, are listed sep- arately and their status is clarified. The purpose of these lists is to update Stone’s Catalogue for the western Canadian region. Few publications relevant to the asilid fauna of the region have appeared since the Catalogue was published. Adisoemarto (1967) summarized the distribution of the robber flies of Alberta, and included some data from surrounding regions. Adisoemarto and Wood (1975) ‘published some British Columbia records in their revision of Dioctria and relatives, as did Martin (1975) in his work on the Asilini and Wilcox on Efferia (1966) and Stenopogon and Scleropogon (1971). Cannings (1989) added a number of species to the Canadian total in a study of the asilid fauna of a Festuca grassland in the Okanagan Valley of British Columbia. The species lists here are annotated with brief comments on range, distribution in the area un- der consideration, and other information. Localities are given for those species represented by only one or two records. Museum collections containing the material examined are: the Cali- fornia Academy of Sciences, San Francisco [CAS]; Canadian National Collection, Ottawa [CNC]; Spencer Entomological Museum, University of B.C., Vancouver [UBC]; Royal British Columbia Museum, Victoria [RBCM]; Royal Ontario Museum, Toronto [ROM]; Pacific Forestry Centre, Victoria [PFC]; University of Guelph, Guelph [UG]. RESULTS Twenty-one species and three genera previously unrecorded in Canada are documented (Table 1). The genera are Callinicus, Coleomyia, and Megaphorus. Twelve other species and two genera (Andrenosoma and Stichopogon) have not previously been reported from British Columbia. Sixteen species are new to the Yukon and seven to the Northwest Territories. 20 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Table 1 Range extensions of Asilidae. Species are newly recorded for the jurisdiction indicated. CAN = Canada; BC = British Columbia; YT = Yukon Territory; NWT = Northwest Territories. SPECIES CAN YT NWT ee) (@) Leptogaster arida Leptogaster fornicata 'Callinicus pollenius 1Coleomyia hinei Cyrtopogon ablautoides Cyrtopogon auratus Cyrtopogon bimacula x 4 Cyrtopogon dasylloides x KK mK x KKK mK x xX Cyrtopogon dubius Cyrtopogon falto Cyrtopogon fumipennis x Cyrtopogon glarealis xX Cyrtopogon lineotarsus x xX xX Cyrtopogon princeps x x x xX Cyrtopogon sansoni Eucyrtopogon diversipilosus x Eucyrtopogon nebulo x Eucyrtopogon punctipennis Heteropogon senilis x Kx xX xx xX Lasiopogon actius Lasiopogon canus 4 x Lasiopogon cinereus Lasiopogon hinei Lasiopogon prima Lasiopogon willametti Nicocles dives Nicocles rufus 2Stichopogon fragilis 2Andrenosoma fulvicaudum Laphria astur x KK x x KKK KK KK ~ re Laphria gilva Laphria index Laphria insignis Laphria janus Laphria milvina Laphria partitor Laphria posticata Laphria sackeni x Laphria ventralis xX Laphria vivax X Laphria vultur x 4 Efferia frewingi x Machimus callidus X Machimus vescus x X |Megaphorus willistoni xX xX ~ XK x KKK XK xx xX 1. Genus is new to Canada 2. Genus is new to British Columbia. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 2] List of Robber Flies New to Canada, British Columbia, Yukon Territory, and Northwest Territories Specific localities are listed when only a few collection sites are known, otherwise a general description of the distribution is given. The faunal element to which the species belongs is in- dicated by the following terms: Beringian: restricted to the northern parts of the region, especially Alaska, the Yukon, and ex- treme northwestern Mackenzie. Boreal: transcontinental in the Boreal Forest and south, to varying degrees, in the western mountains. Cordilleran: mountain forests of western North America. Holarctic: parts of both North America and Eurasia, usually Arctic-Alpine or Boreal Forest species. Intermontane: plateaus and valleys of the western mountain ranges; predominantly grassland species. A few species in this category also spread into the grasslands of the western Great Plains. Pacific Coast: west of the Coast Mountains; lowiand forest or sea beach species. Southern: from coast to coast south of the Boreal Forest, transcontinental at least in the United States; in Canada only in extreme southern areas. Western: western mountains and associated lowlands, often extending into the adjacent areas of the Great Plains. Subfamily Leptogastrinae Leptogaster arida Cole. Western; dry forests and adjacent grasslands of the south coast and southern Interior of British Columbia [CNC, RBCM]. Ranges east to Alberta and south to California. New to Canada and British Columbia. Leptogaster fornicata Martin. Intermontane; dry forests and adjacent grasslands of the south- ern Interior of British Columbia. Pavilion [UBC]; specimens from Osoyoos [RBCM,UBC] are close to this species. Also known from Idaho. New to Canada and British Columbia. Subfamily Dasypogoninae Callinicus pollenius (Cole). Cordilleran; dry forests of the southern Interior of British Colum- bia [CNC, RBCM, UBC, PFC]. South to Wyoming and California. Genus new to Canada and British Columbia. Coleomyia hinei Wilcox and Martin. Cordilleran; dry forests of the southern Interior of British Columbia [CNC, RBCM, UBC]. South to Oregon and Idaho. Genus new to Canada and British Columbia. Cyrtopogon ablautoides Melander. Cordilleran; dry forests of the southern Okanagan Valley (Oliver [CNC]). South to Washington. New to Canada and British Columbia. Cyrtopogon auratus Cole. Cordilleran; subalpine forests of southern British Columbia north to the Cariboo region [CNC, RBCM]. East to Alberta and south to Utah and Wyoming. New to British Columbia. Cyrtopogon bimacula Walker. Boreal; widespread in British Columbia, Yukon (north to Old Crow), and Northwest Territories [CNC, RBCM, UBC]. Trans-Canada south to New Hamp- shire and New Mexico. New to Yukon and Northwest Territories. Cyrtopogon dasylloides Williston. Cordilleran; subalpine forests of southern British Columbia [CNC, RBCM, UBC}. South to California. New to Canada and British Columbia. Cyrtopogon dubius Williston. Cordilleran; subalpine forests of southern Coast Mountains (Squamish, Diamond Head Trail [CNC]). South to Oregon. New to Canada and British Co- lumbia. 2) J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Cyrtopogon falto Walker. Boreal; forests of central British Columbia (Skeena River Valley [CNC]). East to Nova Scotia, south along the Appalachians to Florida. New to British Co- lumbia. Cyrtopogon fumipennis Wilcox and Martin. Cordilleran; mountain forests north to the southern Yukon (Nahanni Range Rd., km 128; Carcross [UBC]). South to Washington and Idaho. New to Yukon. Cyrtopogon glarealis Melander. Cordilleran; forests of the British Columbia Interior north to the central Yukon (Pelly Crossing [UBC]). East to Alberta, south to California and Wyoming. New to Yukon. Cyrtopogon lineotarsus Curran. Cordilleran; forests of the British Columbia Interior (Robson [RBCM]), north to N.W.T. (Yellowknife [CNC]). According to Fisher and Wilcox (1987), C. predator Curran is a synonym of C. lineotarsus; C. predator is known from Fort Fraser and Fort St. James, B.C. [CNC]. East to Alberta, south to Washington and Montana. New to British Columbia and Northwest Territories. Cyrtopogon princeps Osten Sacken. Cordilleran; subalpine forests of the Cascade Mtns. of southwestern British Columbia [RBCM]. South to California. New to Canada and British Columbia. Cyrtopogon sansoni Curran. Cordilleran; Kootenay region of southeastern British Columbia (Robson [CNC]). East to Alberta. New to British Columbia. Eucyrtopogon diversipilosus Curran. Cordilleran; forests of the British Columbia Interior north to the southern Yukon (Carcross [UBC]). East to Alberta. New to Yukon Eucyrtopogon nebulo (Osten Sacken). Cordilleran; dry forests and adjacent grasslands; wide- spread in British Columbia (Cannings 1989) north to the northern Yukon (Old Crow, Mason Hill [RBCM, UBC]). South to California. New to Yukon. Yukon specimens may represent an undescribed species. Eucyrtopogon punctipennis (Melander). Cordilleran; forests of southern British Columbia [CNC, RBCM, PFC]. South to Idaho and Washington. New to Canada and British Colum- bia. Heteropogon senilis (Bigot). Cordilleran; forests of southern British Columbia [CNC, RBCM]. South to California. New to Canada and British Columbia. Lasiopogon actius Melander. Pacific Coast; sand beaches of coastal British Columbia (Queen Charlotte Is. [RBCM]).South to California. New to Canada and British Columbia. Lasiopogon canus Hine. Beringian; widespread in dry forests and streambanks of Yukon, in- cluding shrub tundra; east to Tuktoyaktuk Peninsula, Northwest Territories [CNC, RBCM, ROM, UBC]. Alaska south and east to northwestern Alberta. New to Yukon and Northwest Territories. Lasiopogon cinereus Cole. Cordilleran; forests and streambanks of southern Interior of British Columbia [RBCM, UBC]. East to Alberta, south to Wyoming and California. New to British Columbia. Lasiopogon hinei Cole and Wilcox. Beringian; dry forests and streambanks of Yukon [CAS, CNC, RBCM, ROM, UBC]. Alaska south and east to northwestern Alberta. New to British Columbia and Yukon. Lasiopogon prima Adisoemarto. Beringian; dry forests and streambanks of northern British Columbia and Yukon [CAS, RBCM, ROM, UBC, UG] Northwest Territories (Cache Creek Springs [UBC]). Alaska south and east to northwestern Alberta. New to British Columbia, Yukon and Northwest Territories. Lasiopogon willametti Cole and Wilcox. Pacific Coast; sand beaches of Vancouver Island and sandbanks and bars of lower Fraser River and delta, southwestern British Columbia [RBCM, UBC]. South to northern California. New to Canada and British Columbia. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 23 Nicocles dives (Loew). Cordilleran; dry forests of the southern Interior of British Columbia [CNC, RBCM, UBC]. Listed in Foxlee (1944). South to California. New to Canada and British Columbia. Nicocles rufus (Williston). Pacific Coast; Garry Oak/Arbutus/Douglas-fir woods of southern Vancouver Island and Gulf Islands of southwestern British Columbia [CNC, RBCM, UBC]. South to California. New to Canada and British Columbia. Stichopogon fragilis Back. Intermontane; sandy grasslands of the southern Okanagan Valley (Osoyoos [CNC]). South to New Mexico and Arizona. Species new to Canada; genus new to British Columbia. Subfamily Laphriinae Andrenosoma fulvicaudum (Say). Southern; forests of southern Interior of British Columbia [RBCM, UBC]; noted in Foxlee (1941). Transcontinental in the United States; south to the tropics. Genus and species new to British Columbia. Laphria astur Osten Sacken. Cordilleran; forests of southern British Columbia [CNC, RBCM, UBC]; listed in Foxlee (1941). South to California. New to Canada and British Columbia. Laphria gilva (Linnaeus). Holarctic (Boreal in North America); widespread in forests of British Columbia, Yukon and Northwest Territories [CNC, RBCM, UBC]. Yukon (Dawson, White- horse [CNC]). East to the Atlantic, south to Massachusetts and Oregon. New to Yukon. Laphria index McAtee. Boreal; forests of British Columbia Interior (Robson [RBCM, UBC}). Transcontinental in Canada; south to Virginia. New to British Columbia. Laphria insignis (Banks). Boreal; forests of British Columbia Interior [CNC, RBCM, PFC, UBC], north to the southern Yukon and Northwest Territories. Yukon (Dawson, 14 mi [23 km] E [CNC]; Nahanni Range Rd., km 128 [UBC]). Northwest Territories (Norman Wells [{CNC}). East to Labrador; in the West, south to California. New to British Columbia, Yukon and Northwest Territories. Laphria janus McAtee. Boreal; forests of the British Columbia Interior north to Northwest Ter- ritories (South Nahanni Rd. [CNC]) and Yukon (Alaska Hwy. km 1403, Judas Creek [ROM]). Transcontinental in the Boreal Forest, south to New York and Michigan in the East, Utah and Colorado in the West. New to Northwest Territories and Yukon. Laphria milvina Bromley. Cordilleran; forests of British Columbia Interior [CNC, RBCM, UBC] north to the southern Yukon (Rancheria-Swift River [CNC]). South to Oregon. New to Yukon. Laphria partitor (Banks). Cordilleran; forests of southern Yukon (Slims River delta, Kluane [ROM]) south through British Columbia (CNC, RBCM, UBC) and Washington to Oregon. New to Yukon. Laphria posticata Say. Boreal; forests of the British Columbia Interior [RBCM, UBC] north to the southern Yukon (Carmacks, Whitehorse [CNC]) and Northwest Territories (Fort Simpson, Fort Smith [CNC]). East to the Atlantic, south to New York in the East and British Columbia in the West. New to British Columbia, Yukon and Northwest Territories. Laphria sackeni (Banks). Cordilleran; forests of the southern Interior of British Columbia [RBCM,UBC]. South to California. New to Canada and British Columbia. Laphria ventralis Williston. Pacific Coast; dry forests of southern Vancouver Island and Gulf Is- lands of southwestern British Columbia [CNC, RBCM, PFC, UBC]. South to California. New to Canada and British Columbia. Laphria vivax Williston. Cordilleran; forests of the British Columbia Interior north to the south- er Yukon (Carcross [UBC]). South to New Mexico. New to Yukon. Laphria vultur Osten Sacken. Cordilleran; forests of southern British Columbia south of 51 de- grees N [RBCM, UBC]; listed in Foxlee (1941). South to California. New to Canada and British Columbia. 24 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Subfamily Asilinae Efferia frewingi Wilcox. Western; grasslands of upper (eastern) parts of Kootenay and Colum- bia river valleys in British Columbia [CNC, RBCM, UBC]. Described in Wilcox (1966) from Oregon. East to Saskatchewan, south to Utah and California. New to British Columbia. Machimus callidus (Williston). Cordilleran; Widespread in the forests of British Columbia north to the southern Yukon (Whitehorse [CNC], Snafu Creek [UBC]). South to Oregon. New to Yukon. Machimus vescus (Hine). Cordilleran; dry forests of southern Interior of British Columbia (Oliver [UBC]). South to California. New to Canada and British Columbia. Megaphorus willistoni (Cole). Intermontane; grasslands of southern Okanagan and Similka- meen valleys (Chopaka [RBCM]). South to California and Arizona. Genus new to Canada and British Columbia. Two species recorded from British Columbia in the literature are separated here from the main list because their identification is doubtful and specimens could not be located for confir- mation. If their identification were confirmed, these species would be new to Canada. Cyrto- pogon rejectus Osten Sacken, cited under the name C. positivus, was reported from Port Ren- frew by Hine (1904). A female in the Ohio State Collection identified as this species, apparently by Hine (Hope Mts., 27.vii.1906, R.V. Harvey), is closer to C. fumipennis Wilcox and Martin. Negasilus platyceras (Hine) was reported from Robson by Foxlee (1941). It was identified as Asilus platyceras by Bromley; the specimen cannot be located. The following 25 species were not recorded in Stone et al. (1965) from the region examined herein, but have subsequently been recorded in the references indicated and, in most cases, through additional collections: Subfamily Dasypogoninae Cophura brevicornis (Williston). Western; Ponderosa Pine and Douglas-fir forests and less fre- quently in adjacent grasslands of southern Interior of British Columbia north to the Chilcotin region [CNC, RBCM, UBC]. South and east to Nebraska, Colorado and California. First recorded in Cannings (1989). Dicolonus nigricentrum Adisoemarto and Wood. Intermontane; grasslands of southern Okana- gan and Similkameen valleys. South to Washington and Idaho. First recorded in Adisoe- marto and Wood (1975). Additional specimens from Osoyoos (Blades and Maier 1992) and Penticton (Cannings 1989) [RBCM]. Dicolonus simplex Loew. Pacific Coastal; Garry Oak parkland of southern Vancouver Island and Gulf Islands. South to California. First recorded in Adisoemarto and Wood (1975). Ad- ditional specimens [RBCM, UBC, CNC]. Dioctria henshawi Johnson. Intermontane; grasslands and dry forests of southern Okanagan and Similkameen valleys. South to California and Utah. First recorded in Adisoemarto and Wood (1975). Additional specimens from Osoyoos (Blades and Maier 1992) [RBCM]. Dioctria pusio Osten Sacken. Cordilleran; dry forests and adjacent grasslands of southern Inte- rior of British Columbia. South to Colorado and California. First recorded in Adisoemarto and Wood (1975). Additional specimens from Penticton (Cannings 1989) [RBCM]. Lasiopogon aldrichii Melander. Cordilleran; widespread in mountains of southern Interior of British Columbia, especially in Engelmann Spruce/Subalpine Fir forests. South to Colorado and Utah. First recorded in Adisoemarto (1967). Additional specimens [RBCM, UBC]. Lestomyia sabulona (Osten Sacken). Intermontane; grasslands of southern Okanagan Valley, British Columbia [CNC, RBCM, UBC]. East to Alberta, south to Wyoming and California. First reported in Adisoemarto (1967). Additional specimens (Cannings 1989) [RBCM, UBC]. Myelaphus lobicornis (Osten Sacken). Intermontane; local in southern Interior grasslands of British Columbia, especially where Chrysothamnus nauseosus (Pall.) Britt. (Rabbit-brush) is present. South to Utah and California. First recorded in Adisoemarto and Wood (1975). J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 25 Additional specimens from Penticton [RBCM, UBC, CNC] and Dutch Creek, Columbia Lake [RBCM] (Cannings 1989). Nicocles utahensis Banks. Intermontane; dry forests and grasslands of the southern Interior. East to Alberta, south to Utah and California. Cited in Foxlee (1941) as N. punctipennis Me- lander. Recorded by Adisoemarto (1967). Ospriocerus abdominalis (Say). Western; rare in low elevation grasslands of Thompson, Okanagan, and Similkameen valleys of southern British Columbia. East to Manitoba, south to Pennsylvania, Nebraska and Texas. First recorded in Adisoemarto (1967); additional spec- imens [CNC, RBCM]. Scleropogon bradleyi (Bromley). Pacific Coastal (in the northern part of its range); Garry Oak parklands of southern Vancouver Island and Gulf Islands. South to California. The specimen of S. helvolus Loew listed in Hine (1904) should be referred to this species; it is in the Ohio State Collection and was examined during this study. Specimens recorded in Wilcox (1971) from Lytton in the southern Interior of British Columbia are apparently S. neglectus. Addi- tional specimens [RBCM, UBC]. Scleropogon neglectus (Bromley). Western; widespread in dry, open forests and grasslands of southern British Columbia and prairie provinces. South to New Mexico and Arizona. First recorded in Wilcox (1971). Additional specimens [RBCM, UBC, CNC]. Stenopogon rufibarbis (Bromley). Intermontane; grasslands, especially mesic ones, in southern British Columbia. Also in grasslands of southern Alberta and Saskatchewan. South to Ari- zona and California. First recorded in British Columbia by Adisoemarto (1967). Recorded on the Great Plains as S. obscuriventris Loew by Adisoemarto (1967) (Wilcox 1971). Addi- tional specimens [CNC, RBCM, UBC, PFC]. Subfamily Laphriinae Laphria aimatus McAtee. Cordilleran; dry coniferous forests in the southern Interior of British Columbia and the Alberta mountains. First recorded by Adisoemarto (1967). Additional specimens [CNC, RBCM]. Laphria fernaldi (Back). Cordilleran; widespread in the forests of British Columbia and the mountains of western Alberta. First recorded by Adisoemarto (1967). Additional specimens [CNC, RBCM, UBC, PFC]. Pogonosoma ridingsi Cresson. Cordilleran; dry forests of southern British Columbia (includ- ing coastal and interior areas) and the southern Rocky Mountains of Alberta. P. stricklandi (Adisoemarto) named from Alberta by Adisoemarto (1967) is probably conspecific. Addi- tional specimens [CNC, RBCM, PFC]. Subfamily Asilinae Dicropaltum mesae (Tucker). Western; widespread in grasslands of southern Interior of British Columbia north to the Chilcotin region. Southern Alberta; cited in Adisoemarto (1967) as Asilus mesae (Tucker) and in Martin (1975) in Negasilus, this species is here placed in Di- cropaltum to conform to the proposed treatment of Fisher and Wilcox (1987). Additional specimens [RBCM, UBC] Efferia albibarbis (Macquart). Southern; xeric grasslands of extreme southern Okanagan Val- ley, especially where there is sand [CNC, RBCM, UBC]. Only other Canadian localities are on the beaches of Lake Erie, Ontario [RBCM, CNC, UG]. First recorded in Cannings (1989). Efferia benedicti (Bromley). Intermontane; grasslands of the southern Interior of British Co- lumbia, especially on silty soils. This is the species that Adisoemarto (1967), using the genus Nerax, incorrectly called N. canus (Hine). In British Columbia first recorded by Cannings (1989). Additional specimens [CNC, RBCM, UBC, PFC, UG]. There is no evidence that the species occurs in Alberta despite its inclusion in Adisoemarto (1967) and Strickland (1946). Efferia coulei Wilcox. Intermontane; grasslands, especially mesic ones, of the southern Interior of British Columbia north to the Chilcotin region. Described in Wilcox (1966) from Wash- ington. First recorded in Cannings (1989). Additional specimens [CNC, RBCM, UBC, UG]. 26 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Efferia staminea (Williston). Western; mesic grasslands in southern Interior of British Colum- bia. First reported in British Columbia by Cannings (1989). Additional records [CNC, RBCM, UBC]. Machimus erythrocnemius (Hine). Southern; forests of British Columbia Interior [CNC, RBCM]. First recorded in Adisoemarto (1967). Additional records [RBCM]. Proctacanthus milbertii Macquart. Southern; grasslands of southern Interior of British Colum- bia. First recorded in British Columbia in Cannings (1989). Additional specimens [CNC, RBCM, UBC, PFC]. Proctacanthus occidentalis Hine. Intermontane; grasslands of the southern Interior of British Columbia. First recorded by Cannings (1989). Additional specimens [CNC, RBCM, UBC, PEG]. Rhadiurgus variabilis (Zetterstedt). Holarctic; Boreal in Canada. Widespread in subalpine forests throughout southern British Columbia and the Rocky Mountains of Alberta. Wide- spread in the Boreal Forest across Canada from Yukon to Labrador. Treated as Nigrasilus ni- tidifacies Hine in Stone et al. (1965); the names were synonymized in Cannings (1993). First reported in British Columbia by Hine (1909) and by Cannings (1993) in Yukon and North- west Territories. ACKNOWLEDGEMENTS I am grateful to D.M. Wood (Agriculture Canada, Ottawa) for encouragement and the loan of specimens and to E.M. Fisher (California Department of Agriculture and Food, Sacramento) for identifications and advice. I also thank P. Arnaud, Jr. (California Academy of Sciences, San Francisco), D.C. Darling (Royal Ontario Museum, Toronto), B. Duncan (Pacific Forestry Centre, Victoria), S.M. Marshall (University of Guelph, Guelph), G.G.E. Scudder (University of British Columbia, Vancouver), and C.A. Triplehorn (Ohio State University, Columbus) for allowing me to examine specimens in their care. REFERENCES Adisoemarto, A. 1967. The Asilidae (Diptera) of Alberta. Quaest. Entomol. 3: 3-90. Adisoemarto, A. and D.M. Wood. 1975. The Nearctic species of Dioctria and six related genera (Diptera: Asilidae). Quaest. Entomol. 11: 505-576. Blades, D.C.A. and C.W. Maier. 1992. A survey of grassland and montane arthropods collected in the Osoyoos region of British Columbia. Unpublished report to the South Okanagan Critical Areas Project. 36 pp. Cannings, R.A. 1989. The Robber Flies (Diptera: Asilidae) of a Festuca grassland in the Okanagan Valley, British Co- lumbia. J. Entomol. Soc. Brit. Columbia 86: 14-26. Cannings, R.A. 1993. New synonomy of Rhadiurgus variabilis (Zetterstedt) (Diptera: Asilidae) with notes on mor- phology, natural history, and geographical variation. Can. Entomol. 125: 337-354. Fisher, E.M. and J. Wilcox. 1987. Checklist of Nearctic Asilidae. Unpublished manuscript. Foxlee, H.R. 1941. A list of nineteen species of Asilidae collected at Robson, B.C. (Diptera). Proc. Entomol. Soc. Brit. Columbia 38: 14. Foxlee, H.R. 1944. Records of some flies and wasps collected at Robson, B.C. (Diptera: Asilidae; Hymenoptera: Ich- neumonidae). Proc. Entomol. Soc. Brit. Columbia 41: 26. Hine, J.S. 1904. The Diptera of British Columbia (First Part) Can. Entomol. 36: 85-92. Hine, J.S. 1908. Two new species of Asilidae from British Columbia. Can. Entomol. 40: 202-204. Martin, C.H. 1975. The generic and specific characters of four old and six new Asilini genera in the western United States, Mexico, and Central America (Diptera: Asilidae). Occas. Pap. Calif. Acad. Sci. 119: 1-107. Stone, A., C.W. Sabrosky, W.W. Wirth, R.H. Foote, and J.R. Coulson. 1965. A catalogue of the Diptera of America north of Mexico. U.S. Dept. Agriculture, Agriculture Handbook No. 276. Washington, D.C. 1696 pp. Strickland, E.H. 1946. An annotated list of the Diptera (flies) of Alberta. Additions and Collections. Can. J. Res. Ser.D 24: 157-173. Wilcox, J. 1966. Efferia Coquillett in America north of Mexico (Diptera: Asilidae). Proc. Calif. Acad. Sci. 34(2): 85-234. Wilcox, J. 1971. The genera Stenopogon Loew and Scleropogon Loew in America north of Mexico (Diptera: Asilidae). Occas. Pap. Calif. Acad. Sci. 89: 1-134. Wilcox, J. and C.H. Martin. 1936. A review of the genus Cyrtopogon Loew in North America (Diptera: Asilidae). En- tomol. Amer. 16(1): 1-95. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 27 Insect pest and natural enemy populations in paired organic and conventional apple orchards in the Yakima Valley, Washington ALAN KNIGHT USDA, ARS, 3706 W. NOB HILL BLVD, YAKIMA, WA 98902 ABSTRACT Insect pest and natural enemy populations were evaluated during the 1990 growing season in five paired certified organic and conventional apple orchards in the Yakima Valley, Washington. Each orchard-pair was managed by one grower and had similar conditions of location, extent, cultivars, and tree density. Organic orchards had not been treated with synthetic insecticides for 1-2 years before this study. Fruit injury from codling moth and population densities of phy- tophagous mites, sucking bugs, rosy apple and green aphids, leafminers, leafhoppers, and se- lected natural enemies were monitored throughout the season. Damage from codling moth was over 3% in three of the five organic orchards. Densities of phytophagous mites were high in one conventional orchard at the end of the season. Organic orchards had significantly higher popu- lations of sucking bugs at bloom than did conventional orchards. There was no significant dif- ference between orchard types in the densities of rosy apple aphid colonies per tree, but colonies in conventional orchards had significantly more aphids and significantly less parasitism than in organic orchards. The population density of green aphids was higher in conventional than or- ganic orchards during the second half of the season. There was little difference in numbers of adult leafhoppers caught on sticky traps between orchard types, but captures of a leafhopper egg parasite were significantly higher in organic than in conventional orchards throughout the sea- son. Immature leafminer populations were significantly higher and parasitism of leafminer was significantly lower in conventional than organic orchards after July. Parasitism of codling moth was not found in any orchard. Key words: Codling moth, organic, apple, pest management, aphid, mite, leafhopper, leafminer, egg parasite INTRODUCTION Increased public awareness and changes in societal attitudes towards pesticides (Ott et al. 1991) and increased consumer support for IPM practices (Hollingsworth et al. 1993) are forcing a reconsideration of existing pest management programs in apple production (Prokopy & Croft 1994). The focus of this movement is to develop alternatives to broadspectrum neuroactive insecticides for the major pests in each region. In the western U.S., codling moth, Cydia pomonella (L.) is the key insect pest in apples and conventionally-managed orchards rely on a series of ‘cover sprays’ against this pest during the season (Washington State Co- operative Extension Service 1992). Organophosphate insecticides have been used almost exclusively to manage codling moth during the last 35 years, and resistance has recently been documented (Varela et al. 1993, Knight et al. 1994). The frequent use of organophosphate in- secticides in apple also contributes to outbreaks of secondary pests (Prokopy & Croft 1994), such as mites, sucking bugs, aphids, leafhoppers, and leafminers. The mean number of insecti- cide sprays applied in Washington apple orchards is eight per season (Beers & Brunner 1991). Biological control plays a limited role in managing populations of pests in sprayed orchards, ex- cept for instances where natural enemies have developed insecticide resistance (e.g., predatory mites [Hoyt 1969}). The level of biological control of insect pests which can be established in commercial apple orchards can probably best be viewed by examining populations in certified-organic orchards. Organic orchards cannot be treated with organophosphate, carbamate, pyrethroid, or other syn- thetic insecticides (Washington State Department of Agriculture 1992). Instead, growers must rely ona short list of materials which includes botanicals, microbials, minerals, natural oils, and 28 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 soaps. These materials are thought not to be as disruptive of natural enemies as synthetic insec- ticides. The organic certification program in Washington state began in 1988 with 11 growers having a total of 40 ha of pome fruits. This peaked in 1990 with 100 growers and 800 ha (M. McEvoy, personal communication). The size of the program has stabilized at ca. 0.5% of the to- tal apple production in Washington (350 ha). Little information has been gathered on the suc- cess of organic apple pest management during this brief period. The objective of my study was to compare insect and mite pests and natural enemy population densities in paired organic and conventional apple orchards in the Yakima Valley of Washington. MATERIALS AND METHODS Study sites. In 1990, five apple growers with both organic and conventional orchards in the Yakima Valley were included in this study. Each organic orchard was paired with another or- chard treated conventionally with synthetic insecticides. Orchard-pairs were matched for their similarity in area, cultivar, and planting density. The orchards were primarily ‘Delicious’ in- terplanted with ‘Golden Delicious’ at a density of 450-600 trees per ha and ranged in size from 4-16 ha. Spray practices. Conventional orchards received an average of 3.7 sprays of azinphosmethy1 (Guthion 50W, Miles Chem., Kansas City, MO) directed at codling moth. In contrast, organic orchards were treated with either ryania (Ryan 50, Dunhill Chem., Riverside, CA), granulosis virus (provided by Dr. L. Falcon, Univ. of California, Berkeley), Bacillus thuringiensis Berliner (Dipel 2X, Abbott Labs, N. Chicago, IL), or cryolite (Kryocide 96, Penwalt Chem., Bryan, TX) alone or in various combinations (a mean of 14 sprays of these materials was applied per or- chard). Secondary pests in conventional orchards were treated with a mean of 2.5 sprays of car- bamate and organophosphate insecticides at standard rates (Washington State University Co- operative Extension Service 1992). These included: phosphamidon (Swat 8E, Ciba Geigy, Greensboro, NC), carbaryl (Sevin XLR, Union Carbide, NY, NY), and oxamyl (Vydate 2L, E. I. Dupont de Nemours & Co., Wilmington, DE). Growers applied in organic orchards a mean of 2.0 sprays for secondary pests at standard rates; including soap, pyrethrum, and rotenone (In- tegrated Fertility Management 1990). Pests and Natural Enemies. Population densities of various pest and beneficial arthropods were monitored in each orchard. These included: the phytophagous mites, Tetranychus urticae Koch and Panonychus ulmi (Koch) and the predatory mite, Typhlodromus occidentalis (Nes- bitt); the sucking bug, Campylomma verbasci (Meyer); rosy apple aphid, Dysaphis plantaginea Passerini, a complex of green aphids, Aphis pomi DeGeer, Rhopalosiphum fitchii (Sanderson), and Aphis spiraecola Patch, aphid parasitism, and generalist aphid predators; white apple leafhopper, Typhlocyba pomaria McAtee and a mymarid egg parasitoid, Anagrus sp.; western tentiform leafminer, Phyllonorycter mespilella (Hubner) and levels of leafminer parasitism; and fruit injury by codling moth. Sampling. Sampling was done on 11 and 24 May, 8 and 20 June, 6 and 31 July, 16 and 27 Au- gust, and 10 September. Fruit injury was determined 2-3 July and 27-28 August. Scouts walked transects within each orchard and arbitrarily chose the trees, shoots, and leaves to sample. Mites were sampled by collecting 16 leaves from each of ten trees at each orchard. Leaves were washed in 800 ml of a 50:50 solution of water (with 1 g detergent added) and 25% ETOH for 30 s. The liquid was poured through a fine sieve into a petri plate, and mites were counted un- der a dissecting microscope. C. verbasci nymphs were washed similarly from five blossom clusters collected from each of ten trees per orchard on 23 April. Rosy apple aphids were sam- pled by counting the number of infested shoots observed per 3 min from 10 trees in each orchard on 2-3 July. Ten colonies were collected and the number of living and parasitized aphids and the number of generalist predators within each colony were recorded. Green aphids were sampled by counting the number of aphids on the most infested leaf per shoot from five shoots on each of 10 trees in each orchard. The total number of generalist predators per shoot was also recorded. Adult white apple leafhopper and Anagrus sp. adults were sampled with sticky yellow cards (Trece Inc., Salinas, CA). Five traps were placed at 2.0 m in the tree canopy and were retrieved after 7 d. Data were expressed as the mean number of adults caught per day per trap for each or- J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 29 chard. The number of immature leafminers per 10 leaves was counted from 20 trees in each or- chard by selecting the third leaf down the shoot from the leaf visually selected. Levels of para- sitism were assessed for each generation by dissecting 50 mines from each orchard. Host feed- ing was included as a part of total parasitism (Barrett & Brunner 1990). Fruit injury was determined mid-season and at harvest by inspecting fruit along 40 transects, 20 apples from five consecutive trees (4,000 apples per orchard). Fruit injury for each orchard was weighted by the percentage of the total number of trees of each cultivar. Corrugated cardboard bands were placed around forty trees in each orchard on 10 June and 15 August to determine parasitism of codling moth larvae. Diapausing larvae were kept at 2°C for 120 d and then reared at 22°C un- til the completion of moth and parasitoid emergence. Differences in the mean population counts of pests and natural enemies between organic and conventional orchards were analyzed using a paired sample t-test for each date. RESULTS Pest and Natural Enemies. Phytophagous mite populations were low and populations of predatory mites were high in all orchards during the season (Fig. 1A and 1B). However, on the last sample date, phytophagous mite populations (7: urticae) increased in one conventional or- chard to high levels, more than 20 mites per leaf (Fig. 1A). . Population densities of C. verbasci during bloom were significantly higher in organic than in conventional orchards (mean + SE = 2.0 + 0.5 and 0.1 +0.01 nymphs per five blossom clusters, respectively). Fruit injury at harvest from C. verbasci was detected only in one orchard (2.8% of fruit). Densities of rosy apple aphid colonies per tree did not differ between organic and conven- tional orchards (Fig. 2A). However, the number of living aphids per colony in early July was significantly higher in conventional orchards. In addition, within individual colonies, signifi- cantly higher number of parasitized aphids were found in the organic orchards (Fig. 2B). Preda- tor densities in aphid colonies did not differ between orchard types. Densities of green aphids were low in organic orchards all season (Fig. 3). Densities were much higher in conventional than in organic orchards during July and August and on two dates these differences were significant. Few generalist predators (primarily immature coccinellids, syrphids, and chrysopids) were found on shoots infested with aphids (i.e., less than 0.1 preda- tors per shoot in the organic orchards) but these data are not included here. Few differences were seen in populations of white apple leafhopper between organic and conventional orchards during the season (Fig. 4A). In contrast, density of the egg parasitoid, Anagrus sp., was substantially higher in organic orchards in five of the seven samples (Fig. 4B). Table 1 Summary of fruit injury by codling moth in mid-summer (2-3 July) and just before harvest (27-28 August) in organic and conventional apple orchards, 1990. Percentage fruit injury Mid-summer At Harvest Orchard Organic Conventional Organic Conventional Yi 4.00 0.28 32.48 0.78 nN , 10.18 OH5 21.33 0.23 x3 0.28 0.13 0.83 0.20 Y4 0.13 0.20 3.65 0.90 Y5 023 0.03 0.28 0.05 Mean 2.96 0.16 11.70 0.43 SE 1.95 0.04 6.50 0.17 30 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 100 leaves Mi Organic Conventional 80 60 40 20 Phytophagous mites / 16 6/20 7/06 7/31 8/16 8/27 Sample date 100 leaves MM Organic 80 Conventional 60 40 20 Predatory mites / 16 Sample date Figure 1. Seasonal population densities of (A) phytophagous mites and (B) predatory mites (B) per sample of sixteen leaves per tree from five paired organic and conventional orchards, 1990. ‘**’ denotes a significant difference, p < 0.05. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 31 HM Organic E4 Conventional Rosy apple aphid colonies / tree and aphids / colony SiN Ae NNN Soe ee colonies aphids (x 1,000) 120 HM Organic w Conventional o 100 ~ & mie ° =O 80 5 + eq fo 60 o © b= S > ” @ 40 z 2 ° = 20 Figure 2. Number of rosy apple aphid colonies per tree and aphids per colony (A) and the number of par- asitized aphids and generalist predators per colony (B) from five paired organic and conventional orchards, 2-3 July, 1990. ‘**’ and ‘***’ denotes a significant difference, p < 0.05 and < 0.01, respectively. 32 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Densities of leafminers increased steadily during the season in all orchards but averaged less than 1.5 mines per leaf by the third generation (Fig. 5A). During August and September signif- icantly more mines were found in the conventional than organic orchards. Percent parasitism of leafminer larvae was significantly higher in the organic than in the conventional orchards in both the second and third generations (Fig. 5B). Large numbers of codling moth were recovered from the cardboard bands placed in organic orchards from the summer and overwintering generations (103 and 532 adults emerged, re- spectively), but no parasitoids were collected. Similarly, no parasitoids were collected from the sample of overwintering codling moth from conventional orchards (108 adults emerged). Following the first flight of codling moth the organic orchards Y1 and Y2 had high levels of fruit injury (Table 1). Both of these orchards were adjacent to small unsprayed apple blocks treated unsuccessfully with an experimental sex pheromone membrane dispenser. At harvest, levels of fruit injury from codling moth exceeded 20% in orchards Y1 and Y2. In addition, the organic orchard Y 4 suffered nearly 4% fruit injury at harvest. In contrast, both organic orchards Y3 and Y5 which were situated within 1 km of each other and were fairly isolated from other apple orchards, had less than 1% fruit injury at harvest. Fruit injury in all five conventional or- chards was less than 1% before harvest (Table 1). DISCUSSION This study shows that densities of pests other than codling moth and C. verbasci are similar in organic and conventional orchards or are lower in organic than conventional orchards in the Yakima Valley. The elimination of broad-spectrum insecticides from organic orchards appeared to allow higher levels of natural enemies to develop than in conventional orchards. However, codling moth was not controlled biologically in either orchard type. In contrast, there were low levels of parasitism in abandoned apple orchards (3.4% of the overwintering larvae) and crabapple plantings (7.0% of summer generation and 8.7% of overwintering larvae) in Yakima. All the parasitoids collected were the braconid Ascogaster quadridentatus Wesmael or its hy- perparasitoid Perilampus sp. 40 HM Organic s Conventional D re) a= ae 30 k oO ~ = ” ee © 22 = 20 CD aie oO ” o ® 6 tc 10 @) - 5/11 5/24 6/08 6/20 7/09 7/19 7/317 8/16, Bia7 Sample date Figure 3. Seasonal population densities of green aphids per most infested shoot per tree from five paired organic and conventional orchards, 1990. ‘**’ denotes a significant difference, p < 0.05. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 33 80 HM Organic Conventional 60 7) hes rT) 2. > ro j Oo & , xc SU : =e 40 ; ® / — oe. Pe va Cy] Zt. rere f ws 4 ee ; 3 x : < ; = 20 , ue , @) d 6/20 7/05 7/16 7/31 8/16 8/27 9/10 Sample date H Organic 20 Conventional i?) cS =| ne} om © aS 2. 7) =~ 7) = 10 = = ps ie c m4 _ a 6/11 7/05 7/16 7/31 8/16 8/27 9/10 Sample date Figure 4. Seasonal population density of adult leafhoppers per trap per day (A), and adult Anagrus sp. per trap per day (B) from five paired organic and conventional orchards, 1990. ‘*’, ‘**’, and ‘***’ denotes a significant difference of p < 0.10, < 0.05, and < 0.01, respectively. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 2 ‘= © =) O ie Conventional CO TE CCC CAME SER MT Ley ef UY, BAER Lat OLY oat a Atay Nee es NON SCN oN OER Ne ND oS CARE OC GUE ONY ME nd DOT LRN ORY Sen y SSaeeY «MIT ORT Oey <r SRY omer One SENSE ST Na A eee Ny CNS oN Lae EEN Ce Le OED LATE PAD Ie Riga OOO By De ee AS SIO On Ae Sow NSN NNER NON GOR Sie Weewe Se Scene ON. S8Ae3]| OL / SOdUIIN 8/16. “8727 ori 6/08 -7/0See7 1 1-9% 7/341 5/11 Sample date 100 HH Organic O eS fe) we S co) > (= S) O 80 60 NSE SIN SENN EON Cale NNT EN aN SEEN NONE eee CLA DS EEO EO ELAA 40 SeAIP] JOUIWYyea] JO wusijziseied aHejua010d 20 0) 3rd 2nd 1st Generation Figure 5. Seasonal population densities of western tentiform leafminer per 10 leaves per tree (A) and percent parasitism per generation (B) in organic and conventional orchards, 1990. ‘*’ and ***’ denotes p <0.10 and < 0.05, respectively. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 35 Factors regulating the population of C. verbasci in apple are poorly known (Thistlewood et al. 1990). Fewer C. verbasci nymphs were found during bloom in organic than in conventional apple orchards in British Columbia (McBrien et al., in press). However, these orchards had been organic for 10-15 yrs and were not sprayed during the season with ryania. To manage codling moth in 1990, organic apple growers had to choose between a number of relatively ineffective materials. Typically, organic growers in Washington used weekly sprays of ryania, Bt, and virus, often in combination. The cost of pest management for organic grow- ers compared with a conventional program of azinphosmethy] was 5- to 10-fold higher (Knight, unpublished data), yet despite these costs, many growers suffered economic levels of fruit in- jury. In a spray trial conducted in 1991, fruit injury during the second generation of codling moth was reduced only 81, 47, and 16% with six weekly applications of ryania, virus, and Bt com- pared with an unsprayed check, respectively (Knight, unpublished data). Inspection of these in- juries plus those collected from four commercial orchards treated with combinations of these materials, found that on 65-80% of these apples, codling moth larvae had created only shallow tunnels. The absence of feeding by codling moth larvae prior to entering the fruit makes stom- ach poisons such as Bt (Andermatti et al. 1988) and virus (Falcon et al. 1968) largely ineffec- tive in producing clean fruit, although these materials can potentially be used to reduce popula- tions in later generations (Wearing 1990). Ryania acts as both a contact and stomach poison and was used commonly in the 1950’s in seasonal spray programs (Patterson & MacLellan 1954). However, orchards must be sprayed 6-12 times per season and repeated applications of ryania can cause severe phytotoxicity on some cultivars (Knight, unpublished data). Because of their inability to control codling moth in 1990, two organic growers dropped out of the program. In 1991, a pheromone dispenser system (Isomate-C, Pacific Biocontrol, Davis, CA) was registered for mating disruption of codling moth and its adoption by organic growers during the past three years has been high (> 90% in 1993, M. McEvoy, personal communica- tion). A survey of fifteen organic growers, who adopted mating disruption, found that their use of ryania, Bt, and virus declined by 80% from 1990 to 1993 (Knight, unpublished data). The benefit of using mating disruption for organic growers can be seen by comparing levels of fruit injury in the two organic orchards Y3 and Y5 in 1991. Orchard Y3 adopted mating disruption and had less than 0.4% fruit injury. In contrast, the organic orchard Y5 continued to use virus and Bt and suffered ca. 40% fruit injury from codling moth. Subsequentially, the grower dropped out of the program (Knight, unpublished data). Mating disruption has worked well in apple orchards with low population densities of codling moth (Gut & Brunner 1991, Howell 1992). Yet, in a three year survey of seven paired conven- tional and pheromone-treated orchards in the Yakima Valley, the use of insecticides for sec- ondary pests declined only 20% and levels of biological control of secondary pests did not in- crease with the adoption of mating disruption (Knight, in press). In particular, some apple growers suffered economic losses to leafrollers in orchards treated with mating disruption (Howell 1992, Brunner et al. 1992) and use of organophosphate insecticides for the summer generation of leafroller has become widespread. Interestingly, leafrollers were not observed in orchards in this study in 1990. In the following year, however, 12% fruit injury from the leafrol- ler, Pandemis pyrusana Kearfott, occurred in one orchard. During the following two years, the grower used Bt for both the overwintering and summer generation and fruit injury was less than 0.3% (Knight, unpublished data). Knight (in press) concluded that natural enemies cannot reduce pest populations in apple or- chards sprayed with broad-spectrum insecticides nor can they respond quickly to pest outbreaks in small, isolated pheromone-treated orchards surrounded by sprayed orchards. Creating a sus- tained role for biological control in tree fruit pest management may require area-wide reduction in the use of broad-spectrum insecticides. In the eastern U.S., Prokopy et al. (1990) suggested that apple orchardists adopt a transitional approach towards the use of fewer insecticides and enhanced biological control. In transitional second-stage IPM, orchards would not be treated with synthetic insecticides after petal-fall ex- cept along borders. Adoption of a similar approach in the western U.S. orchards might have to rely on mating disruption to manage codling moth, with Bt possibly mating disruption for 36 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 leafroller. Other pests would either be managed early in the season or later with selective in- secticides and growers would rely more on biological control. Continued study of pest and nat- ural enemy populations in organic orchards using mating disruption for codling moth may pro- vide more evidence for the success of this approach. ACKNOWLEDGEMENTS I thank Ronah Grigg and numerous summer field assistants at the USDA-ARS Laboratory, Yakima, WA who helped collect the data, and the growers for their cooperation. I acknowledge the information on the organic certification program provided by Miles McEvoy, Washington State Department of Agriculture, Olympia, WA, and the critical comments of an earlier draft provided by Larry Hull, Penn State University, Biglerville, PA, and Dave Horton, USDA-ARS, Yakima, WA. REFERENCES Andermatt, M., E. Mani, Th. Wildbolz, and P. Lethey. 1988. Susceptibility of Cydia pomonella to Bacillus thuringien- sis under laboratory and field conditions. Entomol. Exp. Appl. 49: 291-295. Barrett, B. A. and J. F Brunner. 1990. Types of parasitoid-induced mortality, host stage preferences, and sex ratios ex- hibited by Pnigalio flavipes (Hymenoptera: Eulophidae) using Phyllonorycter elmaella (Lepidoptera: Gracillari- idae) as a host. Environ. Entomol. 19: 803-807. Beers, E. H. and J. F Brunner. 1991. Washington state apple and pear pesticide use survey 1989-90. Final report to USDA/NPIAP. Brunner, J. F., L. J. Gut, and A. L. Knight. 1992. Transition of apple and pear orchards to a pheromone-based pest man- agement system. Proc. WA Hort. Assoc. 88: 169-175. Falcon, L. A., W. R. Kane, and R. S. Bethell. 1968. Preliminary evaluation of a granulosis virus for control of the codling moth. J. Econ. Entomol. 61: 1208-1213. Gut, L. J. and J. F Brunner. 1991. Mating disruption as a control for codling moth in Washington. Proc. WA Hort. As- soc. 87: 199-201. Hollingsworth, C. S., M. J. Paschall, N. L. Cohen, and W. M. Coli. 1993. Support in New England for certification and labelling of produce grown using integrated pest management. Amer. J. Altern. Agric. 8: 78-84. Howell, J. F. 1992. Two years of commercial use of Isomate-C to disrupt mating for control of codling moth. Proc. WA Hort. Assoc. 88: 176-181. Hoyt, S.C. 1969. Integrated chemical control of insects and biological control of mites on apple in Washington. J. Econ. Entomol. 62: 74-86. Integrated Fertility Management. 1990. Products and services for natural agriculture. Vol. 7. 47 pp. Knight, A. L. 1994. Grower adoption of mating disruption for codling moth in Yakima Valley, Washington. J. Econ. En- tomol., in press. Knight, A. L., J. F Brunner, and D. Alston. 1994. Survey of azinphosmethy] resistance in codling moth in Washington and Utah. J. Econ. Entomol. 87: 285-292. McBrien, H.L., G. J. R. Judd, and J. H. Borden. Campylomma verbasci (Heteroptera: Miridae): pheromone-based sea- sonal flight patterns and prediction of nymphal densities in apple orchards. J. Econ. Entomol., in press. Ott, S. L., C. L. Huang, and S. K. Misra. 1991. Consumers’ perception of risk from pesticide residues and demands for certification of residue-free produce. pp. 175-188 In: J. A. Caswell (ed.) Economics of food safety. Elsevier, New York. Patterson, N. A. and C. R. MacLellan. 1954. Control of codling moth and other orchard pests with ryania. Annu. Rep. Entomol. Soc Ontario. pp. 25-32. Prokopy, R. J., M. Christie, S. A. Johnson, and M. T. O’Brien. 1990. Transitional step toward second-stage integrated management of arthropod pests of apple in Massachusetts orchards. J. Econ. Entomol. 83: 2405-2410. Prokopy, R. J. and B. A. Croft. 1994. Tree fruit pest management. In R. L. Metcalf and W. H. Luckman (eds.) Intro- duction to pest management. John Wiley & Sons, NY. Thistlewood, H. M. A., J. H. Borden, and R. D. McMullen. 1990. Seasonal abundance of the mullein bug Campylomma verbasci (Meyer) (Heteroptera: Miridae). Can. Entomol. 122: 1045-1058. Varela, L. G., S.C. Welter, V. P. Jones, J. F Brunner, and H. Riedl. 1993. Monitoring and characterization of insecticide resistance in codling moth (Lepidoptera: Tortricidae) in four westem states. J. Econ. Entomol. 86: 1-10. Washington State Department of Agriculture. 1992. Organic food production. Chapter 15.86. pp. 158-160. Washington State University Cooperative Extension Service. 1992. Spray guide for tree fruits in eastern Washington. Washington State Univ. Bull. 0419. 156 pp. Wearing, C. H. 1990. Granulosis virus control of codling moth in Nelson. Proc. N. Z. Weed and Pest Control Conf. 43: 317-321. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 37 Limiting white pine weevil attacks by side and overstory shade in the Prince George Forest Region S.P. TAYLOR BRITISH COLUMBIA FOREST SERVICE, PRINCE GEORGE, CANADA V2L 3H9 and R. D. COZENS BRITISH COLUMBIA FOREST SERVICE, VICTORIA, CANADA V8W 3E7 ABSTRACT A study was initiated in 1985 to measure the effects of side and overstory shade on attack by white pine weevil and on annual growth in interior white spruce. The study was undertaken in the Prince George Forest Region where the weevil causes extensive damage to plantations of interior white spruce. Annual attack rates decreased significantly with increased brush cover. The treatment with side shade was achieved using narrow strip cuts running east and west. Side and overstory shade also reduced annual growth. Results indicate that up to 6% reductions in annual attack rates could be expected for at least 5 years following treatment but that differences in attack rates between treatments took at least three years to appear. INTRODUCTION Young trees of interior white spruce (Picea glauca (Moench) Voss engelmannii Parry ex En- gelm.) are subject to severe damage by the white pine weevil (Pissodes strobi (Peck)) in the Prince George Forest Region (Taylor et al. 1991). This damage results in the formation of stem defects such as crooks and forks (Alfaro 1989), which reduce the merchantability of the tree. Growth loss also occurs since the leader is killed through girdling by the larvae of the weevil. Effects of side or overstory shade on damage levels and weevil behaviour have been reported for interior white spruce, Sitka spruce (Picea sitchensis (Bong.) Carr.) and eastern white pine (Pinus strobus L.). Shade has direct or indirect negative effects on weevil feeding, oviposition activity and brood development (McMullen 1976, Sullivan 1959), on the weevil’s visual re- sponse to the leader silhouettes of the host (VanderSar and Borden 1977), and on survival of overwintering adults (Harman and Kulman 1969, Droska 1982). Shading also reduces the di- ameter and length of the leader to less than the size preferred by the attacking weevils (Harman and Kulman 1969, Taylor et al. 1991) and improves recovery of damaged trees (Alfaro and Omule 1990). The purpose of this study was to quantify the effects of side and overstory shade both on wee- vil attacks and the annual growth of the spruce. METHODS The study was conducted in the Prince George Forest Region in mesic plantations located in the willow variant of the wet cool sub-boreal spruce subzone (see Pojar et al. 1987 for details of this classification system). Three interior white spruce plantations, 50 kilometers east of Prince George, were selected (Fig. 1) to establish this trial after a random walk through them in- dicated an active weevil population. These plantations had been clearcut in 1969, site prepared with a broadcast burn in 1970 and planted in 1971 with 2+1 bareroot spruce seedlings (grown for two years in the nursery greenhouse and for one year in outside transplant beds). Three treatment plots were established in each plantation (Fig. 1 and 2) as follows: e the overstory shade were untreated controls with an intact deciduous overstory that was relatively continuous. The overstory shade trees that overtopped the spruce were: trembling aspen (Populus tremuloides Mich), paper birch (Betula papyrifera Marsh), willow species (Salix spp.) and alder (Alnus crispa spp. sinuata (Regal) Hult); ¢ the no shade treatment had all of the deciduous overstory removed at one time; and 38 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Prince George DAWSON CREEK Forest Region 4/2 km. PLANTATION 3 GEORGE PLANTATION | PLANTATION : Vancouver 784km FIGURE |. Location and design of the plots in the three study plantations. (Treatments for plots: SS = side shade, OS=overstory shade, and NS=no shade) metal pegs to mark treatment boundaries No Shade Overstory (NS) | Shade (OS) 150m FIGURE 2. The plot design for the project, replicated on each of three plantations. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 39 e the side shade treatment consisted of alternate strips with brush removed (no shade) and un- brushed strips (overstory shade), so that the crop trees in the debrushed strips were in partial or side shade from the unbrushed strips. Strips in the side shade treatment were run in an east-west direction to provide shading to the exposed spruce trees when the sun angle was at its maximum. A maximum angle of 58.5° was calculated to occur at noon on the 21st of June at the study sites (Anon. 1965). The sun angle one hour before and after the noon maximum was determined to be 55°. This lower angle was used for the calculations of required strip width. Plots were laid out and cleared mechanically of brush in November of 1985. A stem map of the plots were completed in April 1986 and all spruce trees were permanently identified with numbered metal tags. The past occurrence of weevil attacks was estimated to provide a history of weevil activity within the stand, and annual weevil attacks with leader and diameter growth were periodically recorded. A randomized complete block design was used in this experiment with three blocks (planta- tions) and three silvicultural treatments (plots) within each block. The annual growth and wee- vil rate attack data were subjected to analysis of variance in order to assess potential treatment effects. Data analysis for the weevil attacks was conducted on the sample means for each plot, but data analysis for height increment was based on the individual observations within each plot. Analysis of variance was conducted for annual height growth using the following linear model: Yijk = u + Pi + Tj + PTij + Eijk where u — grand mean Pi — ith plot effect Tj — jth treatment effect PTij — block by treatment interaction Eijk — residual error The least square solution was used to compute the sum of squares and significance test by SAS GLM procedures (SAS 1985, Searle 1987). Preliminary analysis showed that the weevil attack data were not distributed normally. Thus, analysis of variance was not appropriate. As these data were binomially distributed a loglinear model was used for analysis of variance (Bishop, Fienberg and Holland 1975). The SAS CAT- MOD Model (SAS 1985) was used to test the differences in weevil attack on the three treat- ments. Then the Chi-Square Test was used to test for differences between means of attack rates as this was discrete data and the Duncan Multiple Test was used on the height increments, a con- tinuous variable. RESULTS The annual attack rates for 1993 averaged 21.3%, 14.8% and 15.1% for the no shade, side shade and overstory shade treatments respectively (Fig. 3). Significant treatment effects, at the 1% level (Table 1), appeared in 1989 and persisted for the 1990, 1991 and 1993 remeasurement periods. However, no significant differences were found before 1989. No measurements were taken in 1992. The multiple contrasts indicated that all comparisons between no shade versus overstory shade, and between no shade versus side shade were significant from 1989 to 1993 (Table 1). It took three full growing seasons before differences in attack rates between treatments started to show. The maximum difference between the no shade and overstory shade plots was 6% in 1993. Table 1 also indicates that there were interactions at the block level possibly due to the site. These interactions vindicate the decision to use a randomized complete block design. The density of the trees was 951, 1151 and 791 stems per hectare for plantations 1, 2 and 3 respectively. The mean height in 1991, in all plots, was 4.4 + 1.4m (S.D.) and mean DBH was 6.2 cm (+ 2.6 cm). Analysis of variance indicates that there were significant treatment effects at the 1% proba- 40 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Table 1 Effect of three silvicultural treatments (Overstory Shade, Side Shade, and No Shade) on percentage of weevil attacks and results of analysis of variance by category model method. Year 1987 1988 1989 1990 199] 1993 Treatment Average percentage of weevil attacks4 Overstory Shade 1.59a 1.22a 2.37a 2.70a 4.56a 15.10a Side Shade 1.16a i212 3.13a 2.96a 5.83a 14.75a No Shade 2.20a 1.53a 5.39b 5.70b 9.16b 21.30b Sources of variation Probability levels® an Treatment 0.829 0.789 0.002** 0.004** 0.001 ** 0.013** (X75 4) (0:37) (0.45) (12.51) (11.13) CEABS) Ee 18:69) Block 0.001 ** 0.002** 0.001 ** 0.001 4* 0.001 ** 0.346 (X79 4) (24.49) C251) (35:25) (38.79) (27.47) (0.89) a Means within columns, followed by the same letter are not significantly different (p>=0.05) according to X2 pairwise contrasts of categorical model. b (X?5.4) is a Chi-square value under null hypothesis. **Significant difference at 1% level. Table 2 Effect of three silvicultural treatments (Overstory Shade, Side Shade and No Shade) on annual height in- crement (mean + standard error) and results of analysis of variance. Year 1986 1987 1990 1991 Treatment Average annual height increment4 (cm) Overstory Shade 22.4+0.5a 27.9+0.6a 36.1+0.4a 42.8+0.4a Side Shade 21.9+0.4a 25.9+0.5b 38.0+0.4b 44.4+0.5b No Shade 18.5+0.3b 22.0+0.4c 37.6+0.5b 45 .3+0.4b a Means within columns, followed by the same letter are not significantly different at (p=0.05) level ac- cording to Duncan multiple comparison. bility level on all height increments (Table 2). The tests for multiple comparisons accentuate these differences as the order of the significant relationship between the no shade and overstory shade regimes in 1986 are reversed for the 1991 measurements (Table 2). It is interesting to note that height increment also took about three growing seasons before differences started to appear. There are significant differences between plots, but no significant interaction effect between plot and treatment. DISCUSSION The reduction in weevil damage and spruce growth rates reported in this study are similar to those reported in Stiell and Berry (1985) for white pine, McLean (1989) for Sitka spruce and Taylor et al. (unpublished observations) for interior white spruce. The fact that differences in at- tack rates between treatments varied only between | to 6% indicates that measures to modify broadcast herbicide treatments, as suggested in Taylor et al. (unpublished observations), will not be worthwhile until current attack rates exceed at least 15% to 20%. If the attack rates had been at this level when the experiment started, larger differences between treatments may have been noticed. Nonetheless, a side shade regime should significantly reduce the levels of weevil at- tacks in areas of high weevil hazard. 4] J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 £6 co IG ‘sawibas juawjoas) aas4} ay} UBAaMJaq $a}DJ YODJJD JUaIIND Jo UOSIJDdWOD wy ¢ 3JYHNOlgZ YV3SA SQVHS AYOLSYSAO + P!) m > 4 = m = on | z re) < m = oo m >) Co) va) oO JQVHS AYOLSHYSAO —-} Sa0VHS-301S- —- JGVHS ON >< G3WMOVLLVY SWNSLS 31SILdSOSNS JO LN3A0Y¥3d 42 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 The weevil seems to need at least three full growing seasons to manifest its response with in- creased attack rates at a stand level. A partial explanation for this may be either that initial at- tack rates were relatively low when the project started or that the stand level differences in shade levels between treatments were minor. A similar delayed response has been noticed on perma- nent weevil plots in the Southern part of the Region. Increased height increment with decreased shade levels is a well documented phenomenon and helps to support the contention found in Taylor et al. (unpublished observations) that a trade-off exists between reduced weevil attack and decreased spruce growth rates. The exact na- ture of this trade-off must be left for future study. The close relationship observed here between weevil attack rate and annual growth has been commonly accepted for white pine and Sitka spruce for a long time (Wood and McMullen 1983; Kline and Mitchell 1979; and VanderSar and Borden 1977). ACKNOWLEDGEMENTS The following are gratefully acknowledged for their help: Staff in the Prince George Forest District, Tom Landine, Dr. H. Wu, Dr. R. Alfaro, Dr. S. Lindgren and L. Herring. REFERENCES Alfaro, R.I. 1989. Stem defects in Sitka spruce induced by Sitka spruce weevil, Pissodes strobi (Peck), pp. 177-185. In: Insects affecting reforestation: biology and damage. Proceedings of a meeting of the IUFRO Working Group on Insects Affecting Reforestation (S 2.07-03) held under the auspices of the 18th International Congress of Ento- mology, 3-9 July, 1988, Vancouver. R.I. Alfaro and S.G. Glover (eds.). Forestry Canada, Victoria. Alfaro, R.I. and S.A.Y. Omule. 1990. The effect of spacing on Sitka spruce weevil damage to Sitka spruce. Can. J. For. Res. 20: 179-198. Anonymous. 1965. Finding the sun’s true bearing. Civil Aviation Branch, Department of Transport. Ottawa. p 112. Bishop, Y.M.M., S.E. Fienberg and P.W. Holland. 1975. Discrete Multivariate Analysis: Theory and Practice. Cam- bridge, Massachusetts, The MIT Press. Droska, J.S. 1982. Responses of the white pine weevil Pissodes strobi (Peck) (Coleoptera: Curculionidae) to select environmental factors in the fall, M.Sc. thesis, Univ. of Maine, Orono. 60 pp. Harman, D.M. and M.M. Kulman. 1969. Dispersion of released white pine weevils in intra-stand growth types. Ann. Entomol. Soc. Amer. 62: 835-838. Kline, L.N. and R.G. Mitchell. 1979. Insects affecting twigs, terminals and buds. In: Forest Insect Survey and Control. J.A. Rudinsky (ed). O.S.U. Book Stores Inc. p 4772. McLean, J.A. 1989. Effects of red alder overstory on the occurrence of Pissodes strobi (Peck) during the establishment of a Sitka spruce plot, pp. 167-177. In: Insects affecting reforestation: biology and damage. Proceedings of a meet- ing of the IUFRO Working Group on Insects Affecting Reforestation (S 2.07-03) held under the auspices of the 18th International Congress of Entomology, 3-9 July, 1988, Vancouver. R.I. Alfaro and S.G. Glover (eds.). Forestry Canada, Victoria. McMullen, L.H. 1976. Effect of temperature on oviposition and brood development of Pissodes strobi (Coleoptera: Curulionidae). Can. Entomol. 108: 1167-1172. Pojar, J., K. Klinka and D.V. Meidinger. 1987. Biogeoclimatic ecosystem classification in British Columbia. For. Ecol. Manage. 22:119-154. SAS Institute Inc.. 1989. SAS User Guide. Statistics Version 6th Edition. Carry N.C. SAS Institute Inc. Searle, S.R. 1987. Linear models for unbalanced data. John Wiley and Sons Inc. New York. Stiell, W.M. and A.B. Berry. 1985. Limiting white pine weevil attacks by side shade. For. Chron. 61: 5-9. Sullivan, C.R. 1959. The effect of light and temperature on the behaviour of adults of the white pine weevil, Pissodes strobi Peck. Can. Entomol. 91: 213-232. Taylor, S.P., R.I. Alfaro and K. Lewis. 1991. Factors affecting the incidence of white pine weevil damage to white spruce in the Prince George Region at British Columbia. J. Entomol. Soc. Brit. Columbia. 88: 3-7. Taylor, S.P., R.I. Alfaro, C. Delong and L. Rankin. (1994 Unpublished Observations). The effects of overstory shading on white pine weevil damage to interior white spruce and its effects on spruce growth rates. Prince George. VanderSar, T.J. P. and J.H. Borden. 1977. Visual Orientation of Pissodes strobi (Peck) (Coleoptera: Curculionidae) in relation to host selection behaviour. Can. J. Zool. 55: 2042-2049. Wood, R.O. and L.H. McMullen. 1983. Spruce weevil in British Columbia Environment Canada. Canadian Forestry Service. Pacific For. Research Centre. For. Pest Leaflet #2. p 4. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 43 Effects of male to female ratio and number of females per nesting tunnel on sex ratio and number of progeny of the alfalfa leafcutter bee Megachile rotundata (Hymenoptera: Megachilidae) D.F. MAYER DEPARTMENT OF ENTOMOLOGY, WASHINGTON STATE UNIVERSITY, IAREC PROSSER, WA 99350 ABSTRACT This paper reports the results of two 3-year studies on the effects of: 1) the ratio of males to fe- males in the parental generation on percent female progeny; and 2) the ratio of females to nest- ing tunnels on percent female progeny. In study |): there were no significant differences be- tween treatments in percent females in the progeny or total number of nesting cells produced each year. The average percentages of females were 22% in 1990, 27% in 1991, and 28% in 1992. In study 2): there were significantly fewer female progeny with 2 females per tunnel in 1991, and in all years, significantly fewer progeny when the females were crowded. The total number of cells produced was inversely related to crowding with ratios of females per tunnel of i224: 1 and 2:1. Key words: alfalfa leafcutter bee, Megachile rotundata, alfalfa seed INTRODUCTION The alfalfa leafcutter bee, Megachile rotundata (F.), is the primary pollinator of commercial alfalfa seed in the Pacific Northwest of the United States and southwestern Canada (Richards 1984; Mayer et al. 1990). Alfalfa seed growers in the U.S. often purchase leafcutter bees by the gallon from producers in Canada. A gallon of bees contains about 10,000 cells, although the per- cent females in a gallon may vary considerably. Consumers (alfalfa seed growers) prefer the highest possible percent females because females, not males, pollinate the seed crop. Variable sex ratios have been reported for M. rotundata (Osgood 1964, Stephen and Osgood 1965, Waters 1969, Maki and Moffett 1986). Basal cells in the nesting tunnel tend to contain female bees, whereas apical cells contain males (Rothschild 1979). Some studies show that tunnel diameter affects sex ratios (Stephen and Osgood 1965). In wider tunnels the percentage of females produced is greater than in narrower tunnels of the same depth. Klostermeyer et al. (1973) showed that the percent of females increased progres- sively in 4, 4.8 and 6.2 mm diameter holes. However, Rothschild (1979) found no differences in percent females using 6.35 and 7.14 mm diameter holes. Gerber and Klostermeyer (1970) showed sex determination to be a voluntary act for M. ro- tundata concluding that the stimulus which induces the bee to lay fertilized, or female eggs is associated with tunnel depth. Later Gerber and Klostermeyer (1972) showed that altering the depth at which cells were completed changed the probability that a cell would receive a fertil- ized egg. Depths of 4, 8 and 16 cm showed a significant association with sex ratios although there was none with a 12 cm tunnel. Rothschild (1979) also found no association between sex and tunnel with an 11.7 cm tunnel. Stephen and Osgood (1965) found no correlation between sex ratio and tunnel depths of 5.0, 7.5 and 15.0 cm. Jay and Mohr (1987) found sex ratios (male to females) from 1.6:1 to 3:1 despite the use of tunnels of standard length and diameter. They also concluded that there were no significant increases in females produced in replacement nests. Tepedino et al. (1994) in a one-year study showed that intertunnel distance had a signif- icant effect on the percentage of female progeny. Tepedino and Parker (1988) found that the sex ratio of emergent second-generation bees was strongly biased toward females and the sex ratio of diapausing bees was strongly biased toward males: only 35.5% of second generation bees were males compared with 61.7% of those that 44 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 entered diapause. Parker and Tepedino had reported limited evidence of alternation of sex ratio in 1982. Gosek et al. (1988) reported percentages of females in different breeding lines from 0 to 87%, with a mean of 48%; in wild populations it was 45%. An over-abundance of males led to a small number of females in the next generation (one-quarter to one-fifth of normal). The high- est proportion of females (50% above normal) was obtained when the parental generation had only a low number of males. They concluded that the optimal number of males in isolated mat- ing cages 1s about 15% of the population. Gerber and Klostermeyer (1972) and Rothschild (1979) concluded that females act as though they know beforehand the number of cells they will provision per tunnel. They could ‘know’ the number of eggs they will fertilize. I report here results of 2 studies: 1) the effect of the ratio of males to females in the parental generation on percent female progeny; and 2) the effect of the ratio of females to nesting tun- nels on percent female progeny. MATERIALS AND METHODS _ Each year, new nest blocks were prepared by taping laminate wood pieces (lcm x 13cm x 12cm) together with strapping tape to form small blocks with 104 nesting tunnels, and cover- ing the back of each block with aluminum foil. Tunnels were 5mm in diameter and 12cm deep. One nest block was placed in each cage. Each year, loose bee cells were obtained from Mr Pollination Services in Canada during the winter and stored at 3° C for about 36 weeks. In the spring, the cells were removed from stor- age and incubated at 28-29° C. Adults that emerged after about 19-21 days were allowed to fly Table 1 Effect of the ratio of male to female leafcutter bees on percent female progeny and total cells produced. Prosser, WA. 1990 199] 1992 Males:Females % Females Total % Females Total % Females Total 6:1 24a 684a 28a 576a 32a 589a 3:1 19a 683a 24a 664a 30a 66la Ze 26a 726a 3la 660a 29a 694a lL: 18a 606a 29a 867a 2la 588a Means within a column followed by the same letter are not significantly different at the p=0.05 level, Newman-Keuls studentized range test. Table 2 Effect of the ratio of female leafcutter bees to tunnels on percent female progeny and total cells produced. Prosser, WA. 1990 199] 1992 Females:Tunnels % Females Total % Females Total % Females Total [eZ 18a 566a 33a 421a 30a 505a fl 23a 496a 30a 303b 34a 483a 21 22a 181b 19b 300b 28a 286b Means within a column followed by the same letter are not significantly different at the p=0.05 level, Newman-Keuls studentized range test. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 45 in the laboratory and males and females were counted and collected into separate vials off the windows. The adults were then released into the cages containing blooming alfalfa and the nest blocks. For the male-to-female ratio studies, 16 cages (6 x 6 x 1.8 m) and for the females-per-tunnel studies, 12 similar cages were erected over different plots of blooming alfalfa each year at Prosser, WA. For male-to-female ratio studies, 80 females were put in each cage and then males added to obtain a 6:1 ratio in 4 cages, 3:1 in 4 cages, 2:1 in 4 cages, and 1:5 in 4 cages. For fe- male-per-tunnel studies, 52 females were put in 4 cages (1 female:2 tunnels), 104 females were put in 4 cages (1 female:1 tunnel) and 208 females in 4 cages (2 females: 1 tunnel). Males were put in the cages at the same time and in equal number to females (1:1). In 1990, bees were put in the cages on 30 July; in 1991 on 5 July; and in 1992 15 July. The bees foraged and constructed cells in the nest blocks during each season. At the end of the nesting season (August) the bee cells were extracted from the laminate boards, counted and put into cold storage at 3° C. After a chilling period of about 36 weeks, the cells were incubated at 28-29° C, the adults reared out and sexed to determine sex ratios. The data were analyzed as a randomized complete block design by analysis of variance, with Newman-Keuls studentized range test for mean separations (Lund 1989). RESULTS AND DISCUSSION Male to Female Ratio There were no significant differences between treatments in the percent females in the prog- eny in any year (Table 1), and no significant differences between treatments in the total number of cells produced each year. There were no significant differences in the mean percent females in different years (22% in 1990, 27% in 1991, and 28% in 19972). In contrast to Gosek et al. (1988), I found that the ratio of males to females had no effect on percent females in the progeny. This difference could conceivably be attributed to different test conditions, methods, or even differences between races of the alfalfa leafcutter bee. Females per Tunnel In 1991, there was a significantly lower percentage of female progeny produced with 2 fe- males per tunnel (Table 2). In all 3 years, there were significantly fewer progeny produced when the bees were crowded (2:1 ratio) than when uncrowded (1:2 ratio). The total number of cells produced was inversely related to crowding with ratios of females per tunnel of 1:2, 1:1 and 2:1. Large-scale research is needed to confirm these effects in the field. CONCLUSION The percentage of female progeny in any population of alfalfa leafcutter bees appears to de- pend on several, interrelated, factors. It was not affected by different ratios of male to female parents or the number of females released into large cages with a fixed number of wooden tun- nels. Larger numbers of females made significantly fewer cells. The results were consistent over three years except that in one year the percentage of females was reduced in the most crowded condition. ACKNOWLEDGMENTS I thank the Washington Alfalfa Seed Commission and the USDA/ARS for partial funding of this research and J.D. Lunden and M.R. Jasso for their help. 46 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 REFERENCES Gerber, H.S. and E.C. Klostermeyer. 1970. Sex control by bees: a voluntary act of egg fertilization during oviposition. Science 167: 82-84. Gerber, H.S. and E.C. Klostermeyer. 1972. Factors affecting the sex ratio and nesting behavior of the alfalfa leaf- cutter bee. Tech. Bull. Wash. Agric. Sta. 73. 11 pp. Gosek, J., A. Ruszkowski, M. Bilinski and K. Kaczmarska. 1988. The percentage of females in the progeny of the lucerne leafcutter bee (Megachile rotundata) in relation to the percentage of females in the parent generation and to the breeding line and population density. Pszczelnicze Zeszyty Naukowe 32: 99-110. (In Polish). Klostermeyer, E.C., S.J. Mech, Jr. and W.B. Rasmussen. 1973. Sex and weight of Megachile rotundata (Hymenoptera: Megachilidae) progeny associated with provision weights. J. Kans. Entomol. Soc. 46: 536-548. Jay, S.C. and N. Mohr. 1987. The effect of nest replacement on the production of females of the alfalfa leaf-cutter bee Megachile rotundata (F). J. Apicult. Res. 26:69-72. Lund, R.E. 1989. MSUSTAT statistical analysis package 4.12. Montana State University, Bozeman, MT. 133 pp. Maki, D.L. and J.O. Moffett. 1986. Nesting cell position, sex ratios, and emergence times of the alfalfa leafcutting bee, Megachile rotundata (F.) in northwestern Oklahoma. Southwest Entomol. 11: 107-112. Mayer, D.F., J.D. Lunden and E.R. Miliczky. 1990. Effects of fungicides on chalkbrood disease of alfalfa leafcutting bee. Appl. Agric. Res. 5: 223-226. Osgood, C.E. 1964. Foraging and nesting behavior of the leafcutter bee Megachile rotundata (Hymenoptera: Megachil- idae). Can. Entomol. 112: 555-558. Parker F.D. and V.J. Tepedino. 1982. Maternal influence on diapause in the alfalfa leafcutting bee. Ann. Entomol. Soc. Amer. 75: 407-410. Richards, K.W. 1984. Alfalfa leafcutter bee management in Western Canada. Agric. Can. Publ. 1495/E. 53 pp. Rothschild, M. 1979. Factors influencing size and sex ratio in Megachile rotundata (Hymenoptera: Megachilidae). J. Kans. Entomol. Soc. 53:392-401. Stephen, W.P. and C.E. Osgood. 1865. Influence of the tunnel size and nesting material on the sex ratios in a leaf- cutter bee, Megachile rotundata. J. Econ. Entomol. 58:965-968. Tepedino, V.J. and F.D. Parker. 1988. Alternation of sex ratio in a partially bivoltine bee, Megachile rotundata (Hymenoptera: Megachilidae). Ann. Entomol. Soc. Amer. 467-476. Tepedino, V.J., D.R. Frohlich and C.R. Baird. 1994. Effect of intertunnel distance and nest-surface aspect on progeny production rate and sex ratio in the alfalfa leafcutting bee (Hymenoptera: Megachilidae). J. Econ. Entomol. 87: 27-30. Waters, N.D. 1969. Alfalfa pollinators. Idaho Agric. Ext. Serv. Curr. Info. Ser. 106. 2pp. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 47 The role of two eulophid parasitoids in populations of the leafminer, Phyllonorycter mespilella (Lepidoptera:Gracillariidae) in British Columbia J.E. COSSENTINE and L.B. JENSEN AGRICULTURE AND AGRI-FOOD CANADA, RESEARCH CENTRE SUMMERLAND, BRITISH COLUMBIA, CANADA V0H 1Z0 CONTRIBUTION NO. 894 ABSTRACT In 1991, orchards in the Naramata region of the Okanagan valley in British Columbia had significantly larger populations of the leafminer, Phyllonorycter mespilella, than those of the Osoyoos/Oliver region, 50 km south, where parasitism had been shown to keep the miner be- low treatment levels. We questioned if different roles of the parasitoid species caused the dis- crepancy. Leaves were collected and leafminers and parasitoids assessed from overwintering populations and also weekly from May through October (1992) in apple orchards representa- tive of the areas. Pnigalio flavipes and Sympiesis marylandensis were the major parasitoid species overwintering in 52.3 and 46.7% respectively of the P. mespilella mines. The percent- ages of the two species did not differ significantly between the orchards screened in both areas and did not account for the differences in the numbers of overwintering or summer generation mines. P. flavipes was the dominant parasitoid species in both regions through the three summer generations. S. marylandensis was only found at low levels in three of the eight orchards until the second and third generations. Parasitoid-induced-mortality in 1992 did not have a consistent significant impact on intraseasonal leafminer increase. Five of the orchards studied had leafminer populations above treatment thresholds. Key words: Treefruit, biological control, Hymenoptera, leafminer INTRODUCTION Phyllonorycter mespilella (=elmaella) (Hubner) (Lepidopera: Gracillariidae), is a tentiform leafminer that feeds within the leaves of several economically important fruit trees in the Pacific Northwest (Hoyt 1983). Four parasitoid species were associated with this leafminer when it was first established in the orchards of the Okanagan and Similkameen valleys of British Columbia in 1988 (Cossentine and Jensen 1992). Pnigalio flavipes (Ashmead) (Hymenoptera: Eulophi- dae) was identified as the major parasitoid of the leafminer in British Columbian and Washing- ton State orchards (Barrett 1988, Cossentine and Jensen 1992). Parasitism by this species could reduce the host’s intraseasonal population increase and keep its density below treatment levels (Barrett and Brunner 1990). The value of the other three leafminer parasitoids, species of Symp- iesis, Eulophus and Cirrospilus (Hymenoptera: Eulophidae), in control of P. mespilella in the interior of British Columbia have not been studied. In the 1991 apple growing season, orchards in the Naramata area of the Okanagan valley had very high populations of the leafminer. This was in contrast to the well controlled populations of P. mespilella in the Osoyoos and Oliver orchards, about 50 km further south where P. flavipes was first established, and its effective role in regulating the leafminer populations during the summer became evident (Cossentine and Jensen 1992). In the 1992 growing season we sought to determine if the parasitoids and their roles differed between the two areas, and if these dif- ferences could explain the variation in the leafminer populations. MATERIALS AND METHODS In 1992 we selected five orchards in the Naramata area that had high populations of P. mespilella in 1991 and three in the Oliver/Osoyoos area which had low populations that had been well controlled by parasitism in the past. More orchards and leaves were screened in Nara- 48 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 mata, because judging from high leafminer counts in previous years, we expected fewer para- sitoids would be found. We collected leaves in January 1992 (Naramata 200, Oliver/Osoyoos 100) from the orchard floor at each site before winter diapause of the leafminer or parasitoid pupae was broken. Leaves from each orchard were placed in a ventilated 2-1 plastic container and held at room tempera- ture (20-22°C). The containers were checked daily for parasitoid emergence and the adult par- asitoids were frozen until identified and sexed. Representative specimens were identified by sys- tematists at the Centre for Land and Biological Resources Research, Ottawa. Comparisons of emerging parasitoids were based on the assumption that each species would have an equal chance of successfully developing under the described conditions. The leaves from three or- chards in Naramata were so severely torn that mines per leaf could not be assessed. An esti- mated appropriate mass of torn leaves was therefore collected from each of these orchards so that emerging parasitoid adults could be collected and identified. One hundred leaves were collected randomly from the canopy of each orchard weekly from May 7 until October 5, and on October 24. The infestation level was determined by counting the mines per leaf and assessing the mine contents of these leaves. This count included the numbers of living and dead sap-feeders (instars 1-3) and tissue-feeders (instars 4-5), pupae, emerged pu- pae, parasitoid eggs, larvae and pupae, mines with a round parasitoid exit hole, as well as empty mines. Leaves containing parasitoids in any stage of development were placed in ventilated 2-1] plastic containers and the emerging parasitoid adults were aspirated, frozen and later iden- tified and sexed. Pnigalio and Sympiesis spp. cause leafminer mortality both as larvae which feed externally on host larvae as well as adults “host-feeding’ on leafminer larvae and occasionally on pupae (Barrett 1988, Van Driesche and Taub 1983). In the first generation total parasitoid-induced- mortality (PIM) was assessed as the number of mines containing dead leafminers and/or para- sitoids divided by the total number of mines minus the number of empty mines. The fate of the P. mespilella from empty mines could not be determined. In the second and third generations the PIM and total number of mines per leaf were assessed as above; however, mines with emerged pupae, empty mines and parasitoid exit holes were removed from the calculations because they may have occurred in the first generation. The number of parasitoids emerging per mine was de- Table 1 Phyllonorycter mespilella mines per overwintered apple leaf and for each summer generation, assessed on 100 leaves at peak sap- and tissue-feeding stages. Mines per apple leaf Overwintering First Generation Second Generation Third Generation cs (n) sap tissue sap tissue sap tissue Naramata Orchards I 11.00 (200) 0.07 0.06 1.07 1.84 4.82 7.48 2 5.57 (200) 0.36 0.03 1.88 355 5:32 5.78 3. ‘ 0.03 0.02 0.41 179 6.82 {98 4 : 0.00 0.00 0.08 1.03 2.46 6.54 5 : 0.19 0.15 2.02 4.18 9.33 13.94 Osoyoos/Oliver Orchards IE 2.76 (100) 0.10 0.06 27 4,25 14.64 15.64 z: 0.44 (100) 0.02 0.02 0.24 0.58 2.90 2.82 3 1.22 (100) 0.02 0.01 0.75 1.76 7.63 8.10 aleaves were torn and mines per leaf could not be determined. bcount from previous week, orchard cut down. 49 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 ‘UMOP IND PIVYDIO ‘yaaM SNOTAaId WO] sjUNOD, ‘AJUAPI O} PasIaWd s][Npe proyisesed Ou " ‘PSUTLLLID}OP 9q JOU P[NOD S9UIW PUL UO} 39M SIALII , 617 00°0 O10 IZI 00°0 970 II 90°0 67°0 ts cO'0 LI'0 CCl S00 BC 02 sc 8S 00°0 81°O C6 00°0 97°0 68 00°0 9r'0 OS £00 v70 44 C10 000 CLE £0'0 £00 (644 00°0 vO 6S 1 LO'0 Leo 19 000 81°O 9LT a0) Ogee SPILYIO JIAIQ/SOCAOSE) OS q q ILE 00°0 £0'0 601 00°0 L0°0 vil 00°0 6r'0 B B ¢ 3961 90°0 90°0 OS q q 10] L400. ~=— L00 OS 00°0 00°0 B e 4 VST £00 £00 vse 700 90°0 tcl 00°0 LI0 19 00°0 LO°0 eB e c SIZ 00°0 S00 OS q q S7l O10 9¢°0 tL 700 CLO vITI 60°0 OF Oy -C 91 000 O10 OS q q cL £0°0 80°0 LS 00°0 61°0 GGGE 80°0 Cl OF aI SPIVYIO LICUILIEN u ws Id u ws Id u ws Id u ws Jd u ws Jd yuno,y pI, puosag SIL] BULIOJUIMIDAQ uol}e1ouas ploysesed Jad surwi Jod sproyisesed ‘(SOUIW [8]0]=U) SUT DyJazIdsau sajoKsouo]Ay q Jad spioysesed (wig) stapunjCipu sisaiduckg pure (jg) sadianyf o1psiud ¢ PGB 50 J. ENTOMOL. SOc. BRIT. COLUMBIA 91, DECEMBER, 1994 Table 3 Mortality attributed to parasitoids (PIM) per 100 apple leaves at peak tissue-feeding Phyllonorycter mespilella stages within each of three summer generations. Mortality@ First Generation Second Generation Third Generation Naramata Orchards l 38.65 87.9 96.8 2. 32°9 pei, 100.0 3. 8.2 47.0 99.2 4 50.0 34.4 79.5 5 75.8 86.7 99.5 Osoyoos/Oliver Orchards Is 19.7 95.3 87.0 2 42.0 84.2 94.6 3. 30:2 80.5 99.3 “Mortality was considered to include: parasitoid eggs, larvae, pupae, parasitoid exit holes (first generation only) and dead host larvae and pupae divided by total mines (excluding mines containing emply pupae, parasitoid exit holes or empty mines in the second and third generations). Peach value in the table represents the assessment per 100 mines. termined as the total of adult parasitoids divided by the number of mines per leaf assessed as above. Parasitoid and leafminer counts were not averaged over weeks within generations because each sample could not be considered a replicate of an extended stabilized point in the host-par- asitoid life histories (Van Driesche 1983). Rather, the leafminer populations were compared at five individual weeks during maximum sap-feeding and tissue-feeding stages within each gen- eration. PIM was assessed at the peak tissue-feeding stage when conditions were most oppor- tune for parasitism and host-feeding. P. mespilella mines per leaf, parasitoids per mine and PIM were compared between the two regions using an ANOVA (SAS Institute 1985). Percent parasitism, the sex of each parasitoid, mines per leaf and PIM within the overwintering population were compared between the two regions using a correlation procedure (SAS Institute 1985). RESULTS AND DISCUSSION Overwintering population. Leaves collected in January from orchards in the Naramata area contained significantly (p=0.04) higher numbers of mines per leaf than did leaves collected from Oliver and Osoyoos orchards (Table 1). This illustrates the contrasting infestation levels between the two orcharding regions observed in 1991. Emerging total number of overwinter- ing parasitoids per mine did not differ significantly (p>0.05) between the two regions (Table 2). P. flavipes and Sympiesis marylandensis Girault (Hymenoptera: Eulophidae) (identified by J. Huber, Centre for Land and Biological Resources Research, Ottawa) were the parasitoid species most commonly reared from overwintering P. mespilella mines. S. marylandensis is probably the same species of Sympiesis previously recorded as a minor parasitoid of the leafminer in the Okanagan valley (Cossentine and Jensen 1992), although it is not one of the three species of Sympiesis previously cited as parasitizing Phyllonorycter elmaella in the Fraser valley (Do- ganlar and Bierne 1980). P. flavipes represented 52.3% and S. marylandensis 46.7% of the overwintering parasitoid populations in the eight orchards (n=358). This was unexpected as P. flavipes was the dominant parasitoid species in the summer studies of 1988-1990 (Cossentine and Jensen 1992) and was therefore expected to infest a higher proportion of the overwintering mines. Percentage of the J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 51 total population varied from 0 to 85.7% and from 14.3 to 100% for P. flavipes and S. marylan- densis, respectively. The percentages of P. flavipes and S. marylandensis in the overwintering mines did not differ significantly (p>0.05) between the two regions. Barrett and Jorgensen (1986) reported that S. marylandensis was the dominant parasitoid species of the first and third P. elmaella generations in Utah and that P. flavipes was dominant in the second and fourth gen- erations. The percentages of male and female adults of each of the two parasitoid species did not differ significantly (p>0.05) between the two regions (Pnigalio male:78.5%, 61.9%; female: 21.5%, 38.2%; Sympiesis male: 78.7%, 90.5%; female: 21.3%, 9.5%, in the Naramata and Os- oyoos/Oliver regions, respectively). Zagrammosoma multilineatum (Ashmead) (Hymenoptera: Eulophidae), a species not previ- ously recorded from P. mespilella in British Columbia (Cossentine and Jensen 1992, Doganlar and Bierne 1980) represented 6.06% of the parasitoid population emerging from one Naramata A. 9 -+— Mines/leaf 0.30 12.0 Naramata 4 -o- / “flavipes |mine 1 =-e S.marylandens/s |mine 9.0 a 0.20 on | a | 4 4 6.0 ee a | g 3 0.10 UW t i =< nm §=(3.0 ee s : sg 5 = 0.0 See Bare | 0.00 5 LL B. 0.30 - Po ee = ep) S 120 Osoyoos x o < 90 0.20 6.0 0.10 3.0 0.0 0.00 May 27 July2 Aug5 Sept 9 DATE Figure 1. Phyllonorycter mines per leaf and parasitism by Pnigalio and Sympiesis per mine from May to October 1992. A=orchard 1, Naramata; B = orchard 1, Osoyoos/Oliver. 52 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 orchard. Over all orchards this represented only 0.76% (n=385) of the overwintering para- sitoids. Summer populations. The number of sapfeeding mines per leaf did not differ significantly (p>0.05) between the two regions in the first generation (Naramata: x=0.13 mines/leaf, Oliver/Osoyoos: x=0.05 mines/leaf) (Table 1). We then questioned if the percent parasitism by each species independently, or the sex ratio of P. flavipes or S. marylandensis within the over- wintering population, affected the number of P. mespilella mines per leaf or percent of PIM in the first generation. None of these factors in the overwintering population consistently or sig- nificantly (p>0.05) influenced mines per leaf or PIM in the first generation when counts were analyzed as separate regions and as a whole (Tables | and 3). The number of overwintering mines was not significantly correlated with the number of sap-feeding (r=0.2, p=0.63)) or tis- sue-feeding (r=0.65, p=0.23) mines in the first generation. This contradicts Barrett and Brun- ner’s (1990) conclusion that the survival of overwintering leafminers, rather than the seasonal levels of parasitism, determine the leafminers’ year-to-year population dynamics. 1.00 =—#= Eggs 0.80 | =O=- Larvae 0.60 == Pupae PROPORTION IN STAGE 0.60 0.40 0.20 0.00 DATE Figure 2. Proportion in each developmental stage: A = parasitoids Pnigalio and Sympiesis, B = leafminer Phyllonorycter determined from weekly samples May to October 1992 from orchard 1, Naramata. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 53 Throughout both regions, P. flavipes remained the dominant parasitoid species over the three generations. Significantly (p<0.05) more P. flavipes emerged per 100 mines than did any other parasitoid species in all three generations. Despite its major role in the overwintering popula- tions, S. marylandensis represented a small percent of the parasitoids in the first summer gen- eration (Table 2, Fig. 1), increasing in its role as a parasitoid in the second generation. The mean number of mines per leaf did not differ significantly (p>0.05) between the two re- gions in the second generation (Table |). Mortality caused by host-piercing and oviposition of P. flavipes and S. marylandensis in the first generation was expected to be negatively correlated with the number of mines per leaf found in the second and third generations (Barrett and Brun- ner 1990, Cossentine and Jensen 1992, Van Driesche and Taub 1983). This was true only for the Osoyoos/Oliver region where the PIM in the tissue-feeding stage of the first generation was sig- nificantly negatively correlated (r=0.90-0.96, p<0.05) with the mines per leaf in the second gen- eration over a two-week period. The economic treatment threshold for leafminers in apple has been estimated at one sap- feeder per leaf for the first generation, two sap-feeders per leaf for the second generation pro- vided that PIM is <30% in the first generation, and five sap-feeding mines per leaf in the third generation (Hoyt 1987). The only orchard sampled in this study that exceeded this treatment threshold in the second generation was in the Oliver/Osoyoos region. Leafminer counts in this orchard did not exceed thresholds in 1991. Despite finding six of the eight orchards with PIM above 30% in the first generation (Table 3), five of the eight orchards had exceeded the treatment threshold by the third generation (Table 1). To explain the high 1992 P. mespilella populations, the warm weather early in the season in 1992 may have allowed the leafminers to establish large populations before P. flavipes could have a significant controlling effect. Unfortunately, neither emergence of adult P. mespilella nor the parasitoid species was assessed in the spring to judge if their emergences were synchronized. In Connecticut, adult S. marylandensis emerged two to four weeks before its host, Phyllono- rycter blancardella, in the spring (Maier 1984). S. marylandensis, which made up about 50% of the overwintering parasitoid population, did not appear to influence P. mespilella control un- til the second and third generations by which time the leafminer populations were already above economic thresholds in some orchards. The developmental stages of the parasitoids appear to be in synchrony with those of the leafminer host in the first two summer generations (Fig. 2), with the parasitoids pupating just at the end of the P. mespilella’s first generation and the para- sitoid eggs being laid at the beginning of generations two and three. The parasitoids appear to have two generations during the leafminers third (Fig. 2). Parasitoid-induced-mortality increased with generation (Table 3), contrary to what was ob- served by Barrett and Brunner (1990) but they excluded mines judged to be from an earlier gen- eration in their counts. We excluded mines but that were empty or contained an emerged pupa or a parasitoid hole. We do not believe that the dead larvae could be assigned to a particular gen- eration consistently. The high PIM in the second and third generations in our study may be par- tially due to the accumulation of dead larvae from previous generations. However the PIM in the second and third generations was also high when compared to studies done in a similar fashion in the Okanagan valley from 1988 to 1990 (Cossentine and Jensen 1992). These high percentages indicate that a low number of live leafminers would be found in the 1992-93 over- wintering mines. This must, at least in part, account for the low populations of P. mespilella ob- served in the summer of 1993. We conclude that the percentage of P. flavipes and S. marylandensis in the overwintering leafminer population of 1991-92 did not differ between the orchards screened in Naramata and Oliver/Osoyoos, and could not explain the differences in the number of first generation mines in any of the eight orchards. We found P. flavipes to be the dominant parasitoid in the three sum- mer generations. S. marylandensis did not start to participate within the complex, except at low levels in three orchards, until the second generation. Neither the Eulophus or Cirrospilus species previously found parasitizing the leafminer in the south Okanagan valley of British Columbia were found in the orchards studied. The leafminer parasitoid complex is usually an efficient and effective biological control of the 54 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 host populations. In 1992 leafminers exceeded economic thresholds in orchards in the Okana- gan valley. Neither P. flavipes or S. marylandensis had a significant influence on intraseasonal leafminer increase. However, increasing season-long PIM had a dramatic impact on the num- ber of leafminers entering overwintering diapause in the fall of 1992. ACKNOWLEDGEMENTS We thank Debbie Bensen for her technical assistance and Mark Gardiner for preparing the graphs. REFERENCES Barrett, B.A. 1988. The population dynamics of Pnigalio flavipes (Hymenoptera: Eulophidae), the major parasitoid of Phyllonorycter elmaella (Lepidoptera: Gracillariidae) in central Washington apple orchards. Ph.D. dissertation, Washington State University, Pullman. Barrett, B.A. and J.F. Brunner. 1990. Temporal distribution of Phyllonorycter elmaella (Lepidoptera:Gracillariidae) and its major parasitoid Pnigalio flavipes (Hymenoptera: Eulophidae), in Washington apple orchards. Environ. Ento- mol. 19(2):362-369. Barrett, B.A. and C.D. Jorgensen. 1986. Parasitoids of the western tentiform leafminer Phyllonorycter elmaella (Lep- idoptera:Gracillariidae), in Utah apple orchards. Environ. Entomol. 15:635-641. Cossentine, J.E. and L.B. Jensen. 1992. Establishment of Phyllonorycter mespilella (Hubner) (Lepidoptera: Gracillari- idae) and its parasitoid, Pnigalio flavipes (Hymenoptera:Eulophidae), in fruit orchards in the Okanagan and Sim- ilkameen valleys of British Columbia. J. Entomol. Soc. Brit. Columbia. 89: 18-24. Doganlar, M. and B. Bierne. 1980. Parasites of Phyllonorycter elmaella (Lep.: Gracilariidae) on apple in the Vancou- ver district, British Columbia. Can. Entomol. 112:314. Hoyt, S. 1983. Biology and control of the western tentiform leafminer. Proc. WA Hort. Assoc. 79:115-118. Hoyt, S. C. 1987. Impact and thresholds of the leafminer on apple. pp. 7-9. In: Leafminer short course. Washington State University, College of Agriculture and Home Economics, Cooperative Extension Service. 17 p. Maier. C. T. 1984. Abundance and phenology of parasitoids of the spotted tentiform leafminer, Phyllonorycter blan- cardella (Lepidoptera:Gracillariidae), in Connecticut. Can. Entomol. 116:443-449. SAS Institute. 1985. SAS User’s Guide: Statistics, Version 5 edition. SAS Institute, Cary, N.C. 956 pp. Van Driesche, R. G. 1983. Meaning of “Percent Parasitism” in studies of insect parasitoids. Environ. Entomol. 12(6): 1611-1622. Van Driesche, R. G. and G. Taub. 1983. Impact of parasitoids on Phyllonorycter \leafminers infesting apples in Massa- chusetts, U.S.A. Prot. Ecol. 5:303-317. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 55 Notes on the biology and rearing of the carrion fly Prochyliza brevicornis (Melander) (Diptera: Piophilidae) A. SYED DEPARTMENT OF BIOLOGICAL SCIENCES, SIMON FRASER UNIVERSITY BURNABY, B.C., CANADA VS5A 1S6 ABSTRACT I describe the first successful rearing of Prochyliza brevicornis (Melander) in the laboratory on a variety of media. The average developmental period from egg to adult for non-diapausing in- dividuals was 42-47 days with a range of 32-74 days. Best survival of those that emerged as adults (16-32 % ) was on ox-tail bones and ground beef. The majority of the larvae in each gen- eration remained quiescent or did not pupate for up to six months which probably indicates an obligatory overwintering diapause in this species. Key words: Diptera, Piophilidae, British Columbia, forensic entomology, carrion INTRODUCTION Piophilids, also known as carrion flies, are commonest in northern temperate areas (Danks 1980; McAlpine 1977, 1987). They grow and develop on proteinaceous substances such as an- imal carrion, bone and bone marrow, cheese, fish and cured meat (Simmons 1927), corpses (Oldroyd 1964, Nourteva 1977; Smith 1986), hoofs and horns (Bishop 1917), human excreta (Howard 1900) and in household garbage (McAlpine 1977). Melander (1924) reviewed the family Piophilidae and described Prochyliza brevicornis (Me- lander) as a new species. It occurred usually in the months of July-August in some localities in Yellowstone Park, Montana and in Chicago, Illinois in the U.S.A. and in British Columbia, Canada. The revised classification of Piophilidae by McAlpine (1977) lists eight species under the genus Prochyliza. Very little information is available on the biology and rearing of the members of this family except for a few species such as Piophila casei (L). Herein I report on some aspects of the rear- ing and biology of Prochyliza brevicornis. Adults of P. brevicornis emerging from a forensic sample of insects brought to Simon Fraser University from Sprott lake , B.C. were used to start a colony for rearing and observations. Their identification was confirmed by Dr. J.L. McAlpine at the Biosystematics Research Centre, Agriculture Canada, Ottawa. MATERIALS AND METHODS I reared P. brevicornis for three successive generations at 26 +1°C, 50% +5% RH, with a 12L:12D photoperiod. Seventeen newly emerged adults serving as a starter colony were placed in 10x10x10 cm wooden cages with a clear acrylic plastic front and a Saran screen at the rear. For second and third generation rearing 40 and 8 adults were caged respectively. Sugar cubes and skim milk powder in a 5.0 cm diam petri dish were provided as food, and water was sup- plied in conical flask with dental cotton wicks. Ovipositional substrates such as uncooked ox- tail bones, ground beef, chicken wings were provided in a 5.0 cm diam. petri dish and placed inside the adult cage. For larval rearing the above three substrates as well as beef salami and processed cheddar cheese slices were used. Larvae were reared in 41 jars. The medium was on a layer of paper towels and was covered with facial tissue to provide dry surfaces for pupation. RESULTS AND DISCUSSION Adults mated after emergence as soon as they were released inside the cage. Mating lasted from 15 sec to 15 min. Males mounted the females during copulation and made vigorous jerks from side to side. In some cases two males were in copula at the same time with one female. 56 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Table 1 Development (in days) on ox-tail and ground beef of P.brevicornis for three generations at 26 + 1°C, 50+5%R and 12L:12D. Developmental Generation | Generation 2 Generation 3 stage Duration Duration Duration N Mean+SE Range N Mean+SE Range N Mean+SE Range eggs 150 1.520:3.-- 1,022.0 200 1,540.3. £.0-2.0 150 1.540.3. 1.0-2.0 larvae 36 3646.2 23-65 19 3344.4 28-40 129 3842.8 33-43 pupae 24° 8.3409 7-13 ASO, TIES Ova 49 7.540.6 6-8 total 24 = 41.945.9 32-74 48 42.4+1.4 37-47 49 47.542.4 43-51 During the course of rearing four females and eight males were found dead after such dual copulation. Under the dissecting microscope, the detached genitalia of one male were observed to be fused externally with the female genitalia. The other males died attached to females. This is evidence that dual mating with one female might be common in this species. Simmons (1927) reported a similar phenomenon for Piophila casei (L.) in which adults of advanced age can copulate but not separate in the laboratory and die in copula. Eggs were laid singly or in clusters. Most oviposition occurred during 3-5 days after mating. Several ovipositional substrates, such as uncooked chicken wings, ground beef, cheese slices and ox-tail, were offered to mated females. Ox-tail appeared to be the preferred substrate for egg laying. Ox-tail bone dries rapidly when left at room temperature for 1-2 days and is much drier than chicken wings or ground beef. It is quite likely that the putrifying fat around the meat and bones stimulates egg laying. Eggs hatched in 24-48 h at 26°C. Newly hatched larvae were 1.5-2.0 mm long, and were very soft and fragile. Second instar larvae were 2-3 mm long, and could be distinguished by their prominent slender mouth hooks. The final instars were 5-6 mm long, and could be readily recognized by the presence of strong mouth hooks and their skipping behavior. The larva skips by bending its body in the shape of a ring and hooks its oral claws over the sharp angle formed by the ventral edge of the posterior beveled truncation. It then pulls hard and the hold is suddenly released resulting in snap throw- ing of the insect in the air (Simmons 1927). Larvae grew well on ground beef or ox-tail bones. Some trials were made by placing second and third instar larvae on beef salami, chicken wings and cheese in Petri dishes. No development occurred on beef salami and all larvae either died or were overtaken by mould or bacterial growth. Similarly development on chicken wings or cheese slices resulted in only a few pupae. The larvae reared on ox-tail bones grew well up to the third instar and slowly started disap- pearing. There was no sign of escape from jars but a close examination of the ox-tail pieces re- vealed that larvae had entered the bones and hard ligaments. No attempt was made to extract them. Larvae on ground beef were given fresh portions of ground beef every two weeks. A froth would appear the next day on the fresh meat where larvae congregate. This could be a result of bacterial activity. Most of the larvae growing either on ground beef or ox-tail bones did not pu- pate and remained quiescent for up to six months, after which the cultures were either discarded or observations terminated. Simmons (1927) reported that retarded growth of piophilid larvae was caused by low temperature or starvation as a result of desiccation of food. Because none of these two factors could have occurred in my cultures, the quiescent larvae had probably entered an obligatory diapause. The total larval period lasted from 23-65 days for those larvae which pu- pated (Table 1). Third instar larvae in their skipping stage wandered around apparently in search of dry places for pupation. The pupal period lasted 4-13 days. The total developmental period from egg to adult of 121 insects that developed successfully was 32-74 days. The yield of the insects reared to adulthood was 16-32 % (Table 1). J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 a7 In the field, Piophilids infest vertebrate cadavers at the decompositional stage when fatty acids are formed (Johnston and Villeneuve 1897, Nourteva 1977). Thus oxtail bones may be a more suitable substrate for development than fresh ground beef or chicken wings. Piophilids have been used as forensic indicators to establish the season and year of their in- festation of human remains ( Skinner ef al. 1988; Smith 1986 ). In view of its prolonged and asynchronous larval development in the laboratory, and its apparent obligatory diapause, this in- sect would be a poor indicator of the elapsed time since death, especially if it were the only in- sect found on the remains. ACKNOWLEDGEMENT I thank Dr. J.H. Borden, Center for Pest Management, Dept of Biological Sciences, Simon Fraser University, Burnaby, B.C., for review of the manuscript. REFERENCES Bishop, F.C. 1917. Some problems in insect control about abattoirs and packing houses. J.Econ.Entomol. 10: 260-277. Danks, H.V. 1980. Arthropods of Polar Bear Pass Bathurst Island, Arctic Canada. Syllogeus (Nat. Hist. Mus. Can.) 25: 1-68. Howard, L.O. 1900. A contribution to the study of insect fauna of human excrement. Proc.Wash. Acad. Sci. 2: 541-604. Johnston, W.G. and G. Villeneuve. 1897 On the medico-legal application of entomology. Montreal Med. J. 24: 81-90. Melander, A.L. 1924. Review of the dipterous family Piophilidae. Psyche 31: 78-86 McAlpine, J.L. 1977. A revised classification of the Piophilidae including ‘Neottiophilidae’ and ‘Thyriophoridae’ (Diptera: Schizophora). Mem. Entomol. Soc. Can. 103: 66 pp. McAlpine, J.L. 1987. (ed.) Manual of Nearctic Diptera. Vol. 2. Agriculture Canada Research Branch, monograph 28, Supply and Services Canada, Hull. Nourteva, P. 1977. Sarcosaprophagus insects as forensic indicators In:Tedeschi,C.G., Eckert,W.G. & Tedeschi,L.G. (eds.) Forensic Medicine, a study in Trauma and Environmental hazards. Vol. II Physical Trauma: 1072-1095, Saunders Philadelphia. Oldroyd H. 1964. The natural history of flies. W.W. Norton & Co., N.Y. 324 pp. Simmons, P. 1927. The Cheese skipper as a pest in cured meats. Bull.U.S.Dept.Agric. 1453: 51-55 pp. Skinner, M., A. Syed, J. Farrell and J.H. Borden. 1988. Case report in forensic anthropology — animal and insect fac- tors in decomposition of a homicide victim. Can. J. Forensic. Sci. 21(182):71-81. Smith, K.G.V. 1986. Manual of forensic entomology. British Museum (Nat. Hist.), Comstock Pub. Assoc. 205 pp. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 59 Biological control of the two-spotted spider mite in raspberries with the predator mite, Phytoseiulus persimilis L. WOOD!, D.A. RAWORTH?, and M. MACKAUER! ICENTRE FOR PEST MANAGEMENT, DEPARTMENT OF BIOLOGICAL SCIENCES SIMON FRASER UNIVERSITY, BURNABY, B.C. V5A 1S6 2PACIFIC AGRICULTURE RESEARCH CENTRE AND AGRI-FOOD CANADA, 6660 N.W. MARINE DRIVE, VANCOUVER, B.C. V6T 1X2 ABSTRACT Phytoseiulus persimilis was released to control the two-spotted spider mite, Tetranychus ur- ticae, in field raspberries at Agassiz, B.C. The mite predators became established and responded numerically to the prey in the treatment plots. For a period of 8 weeks after release, the num- bers of T: urticae were consistently lower in the treatment plots than in the controls. Differences in numbers of 7: urticae between the treatments and the controls were significant on two dates. Key words: TJetranychus urticae, Phytoseiulus persimilis, Rubus idaeus, biological control, Fraser Valley INTRODUCTION The two-spotted spider mite, Tetranychus urticae (Acari: Phytoseiidae) Koch is a common pest of raspberries in British Columbia. A severe infestation can result in almost complete de- foliation by August. Photosynthetic reserves necessary for cold hardiness are lost if premature defoliation occurs (Jennings et a/. 1964). An infestation in the autumn can result in reduced bud survival during the following winter (Doughty et al. 1972). Weak plants leaf out earlier in the spring, and are thus more susceptible to late frosts than healthy plants (W.Peters, District Hor- ticulturist, Abbotsford, B.C., personal communication). Phytoseiids are widely used for the biological control of spider mites on various greenhouse crops (Costello and Elliott 1981; Mori et al. 1989; Tanigoshi 1982). Because of its high vorac- ity, short developmental time, high fecundity (Laing and Huffaker 1969) and good dispersal ability (McMurtry 1982), Phytoseiulus persimilis Athias-Henriot is an important predator of T- urticae in greenhouses. In addition, P. persimilis has also been successfully used for mite con- trol in field strawberries in England, California and New Zealand (Easterbrook 1988; Oatman et al. 1968; Waite 1988). We describe the results of an experiment to determine the efficacy of P. persimilis as a bio- logical control agent of T: urticae on raspberry crops in the Lower Fraser Valley. MATERIALS AND METHODS The experiment was done in a plot of nine rows of red raspberries, Rubus idaeus L., at the Agriculture Canada Research Station in Agassiz. Each row consisted of four eight meter sec- tions separated by two meters of bare ground. Three treatments and a control were assigned at random within a row. This was replicated five times on alternate rows, leaving a buffer row be- tween treatments. We released T. urticae, obtained from Applied Bionomics (Box 2637, Sidney, B.C. V8L 4C1), on 11 May, 1989 by placing three pieces of mite-infested bush bean leaf (Phaseolus vulgaris cv Provider) per stool ( a group of five raspberry canes derived from the same root) onto the raspberry foliage in each plot. The procedure was repeated on 9 and 27 July because the mites did not become established owing to wet, cold weather. The predator P. per- similis was introduced on 2 August when a sample of 30 leaflets per treatment indicated den- sity of 0.70 T. urticae per leaflet. The bean leaves on which the predators were supplied were stapled onto the raspberry foliage in the middle of the canopy in numbers according to the fol- lowing ratios of adult females to predators: 1:50 (High); 1:100 (Medium); and 1:200 (Low); and a control. 60 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 60 & Numbers / leaflet (direct counts) 0 20 40 60 Numbers / leaflet (brushed counts) Figure 1. The relationship between estimated numbers of Tetranychus urticae on raspberry leaflets by di- rect counts and counts after removal with a mite-brushing machine. 8 0.12 7 A B ® Ss — 6 0.08 \ = Ps En 0.04 = | D 2 = 0.00 2 4 6 8 2 4 6 8 Time (wk) Figure 2. Population trends of Tetranychus urticae (A) and Phytoseiulus persimilis (B) in raspberry plots at Agassiz, B.C., 1989. Each point is the average of five replicates for the predator/prey treatments: 1:50,(@); 1:100 (4) ; 1:200 (@); and control,(*). One average standard error of a given mean density was 1.491 (A) and 0.03(B) mites per leaflet. Time zero was 2 August when P. persimilis was introduced. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 61 Mites were sampled on 13 August and at weekly intervals thereafter until 1 October. Sam- ples consisted of 30 leaflets per replicate, 10 leaflets picked equally from the top, middle, and bottom of the plant. The mites were removed from the leaves with a mite-brushing machine (J.G.H. Edwards, Llanfair Orchards, RR1, Okanagan Falls, B.C.), and all stages other than eggs were counted at 10X magnification under a dissecting microscope. Brushed-mite counts were compared to direct counts of mites on leaves. Twenty-one leaflets were picked at random from raspberry plants that were infested with T- urticae. The mites were counted under a dissecting microscope. Each leaflet was then passed through the mite-brushing machine (Henderson and McBurnie 1943), and the T: urticae were counted again. The data were analyzed using SAS® REG and GLM Anova procedure with repeated measures (SAS Institute Inc. 1985). The GLM analyses were performed on log- and square- root-transformed, and untransformed data with similar results. The results reported are from analyses of untransformed data. RESULTS AND DISCUSSION The regression of direct counts (y) on brushed-mite counts (x) (Fig. 1; r2 = 0.732; p < 0.01; y = 7.74 + 0.82 x) was linear since the addition of x2 to the equation was not significant (p > 0.05). The x-intercept was not significantly different from zero (p > 0.05). The data ob- tained using the mite brushing machine were therefore analyzed without calibration. The population trends for T: urticae in the three treatments and the controls followed a simi- lar pattern during the first 2.5 weeks after release, then the numbers diverged (Fig. 2A). Over- all differences between treatments were not significant (p > 0.05), but contrast analysis using Bonferroni’s method showed significant differences between the High treatment and the con- trols at 4.5 weeks (p < 0.05), and between the Medium treatment and the control at 4.5 and 5.5 weeks (p < 0.05). Two-spotted spider mite population levels in the High and Medium treatments maintained the same position relative to the controls through the rest of the experiment but v were not significantly different from the controls (p > 0.05). Phytoseiulus persimilis became established in the treatment plots at low levels and followed a pattern of population fluctuations similar to that of T: urticae (Fig. 2B). Average P. persimilis numbers increased almost ten-fold within 3.5 weeks. The numerical response was analyzed by regressing average numbers of P. persimilis on average numbers of T: urticae for each treatment (High, r2 = 0.604, p = 0.023; Medium, r2 = 0.608, p = 0.023; Low, r2 = 0.857, p = 0.001; and controls, r2 = 0.309, p = 0.153). The data indicate that P. persimilis was able to find its prey and reproduce when prey were abundant. The experiment shows that P. persimilis, which is not native to B.C., can establish and sur- vive in a raspberry field during the summer, for at least 8.5 weeks, at a prey density of 0.7-6.0 T. urticae per leaflet. Significant treatment effects on two dates indicate that P. persimilis may reduce T: urticae numbers at both a 1:50 and 1:100 predator/prey ratio. The results are in agree- ment with other research showing that, in general, agents should be released at a predator-prey ratio of no less than 1:100 (Hoy et al. 1982; and Mori et al. 1989). ACKNOWLEDGMENTS We thank the Agriculture Canada Research Station at Agassiz and Dr. Stan Freeman and Dr. Dave Gillespie for the use of their raspberry field plots and laboratory facilities, and Ward Strong who suggested the project. The principal author, Leslie Wood, thanks her family for supporting her efforts over a long period. 62 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 REFERENCES Costello, R.A. and D.P. Elliott. 1981. Integrated control of mites and whiteflies in greenhouses. B.C. Min. Agric. and Food 81-5, 15 pp. Doughty, C.C., P.C. Crandall and C.H. Shanks. 1972. Cold injury to red raspberries and the effect of premature defoli- ation and mite damage. J. Amer. Soc. Hort. Sci. 97:670-673. Easterbrook, M.A. 1988. Integrated control of two-spotted spider mite on strawberry. Proc. Brighton Crop Protection Conference 3C-14:241-244. Henderson, C.F. and H.V. McBurnie. 1943. Sampling techniques for determining populations of the citrus red mite and its predators. Circ. U.S. Dep. Agric. 671. Hoy, M.A., D. Castro and C. Cahn. 1982. Two methods for large-scale production of pesticide-resistant strains of the spider mite predator Metaseiulus occidentalis (Nesbitt) (Acarina, Phytoseiidae). Z. Angew. Entomol. 94: 1-9. Jennings, D.L., M.M. Anderson and C.R. Wood. 1964. Observations on a severe occurrence of red raspberry cane death in Scotland. Hort. Res. 4:65-77. Laing, J.E. and C.B. Huffaker. 1969. Comparative studies of predation by Phytoseiulus persimilis Athias-Henriot and Metaseiulus occidentalis (Nesbitt) (Acarina: Phytoseiidae) on populations of Tetranychus urticae Koch (Acarina: Tetranychidae). Res. Pop. Ecol. 11:105-126. McMurtry, J.A. 1982. The use of phytosetids for biological control: progress and future prospects. /n: Recent Advances in Knowledge of the Phytoseiidae. M.A. Hoy (ed). Univ. Calif. Publ. Agric. Sci. 3284. Mori, H., Y. Saito and H. Nakao. 1989. Use of predatory mite to control spider mite (Acarina, Tetranychidae) in Japan. Proc. Intl. Seminar on the use of parasitoids and predators to control agricultural pests, Tsukuba, Japan, Oct. 2-7, 1989. Oatman, E.R., J.A. McMurtry and V. Voth. 1968. Suppression of the two-spotted spider mite on strawberry with mass releases of Phytoseiulus persimilis. J. Econ. Entomol. 61:1517-1521. SAS Institute Inc. 1985. SAS® User’s Guide: Statistics, Version 5 Edition. Cary, NC: SAS Institute Inc., 956 pp. Tanigoshi, L.K. 1982. The use of phytoseiids for biological control: progress and future prospects. Recent Advances in Knowledge of the Phytosetidae. M.A. Hoy (ed). Univ.Calif. Publ. Agric. Sci. 3284. Waite, G.K. 1988. Integrated control of Tetranychus urticae in strawberries in south-east Queensland. Exp. Appl. Ac- arology 5: 23-32. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 63 Evaluation of monitoring methods for western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), during the blossom period of ‘Granny Smith’ apples S.J. BRADLEY AND D.F. MAYER DEPARTMENT OF ENTOMOLOGY, WASHINGTON STATE UNIVERSITY, PROSSER, WA 99350 ABSTRACT Commercial sticky board traps (150 x 100 mm) of three different colors (blue, white or yellow) were treated with one of two chemical attractants (p-anisaldehyde and ethyl nicotinate) and with the solvent ethanol. Blue and white traps caught four and three times more thrips respec- tively than yellow traps. Attractants improved catches by only about 20% and were not consid- ered economical. If traps are used, a plain blue trap is recommended. Trapping, beating tray and flower cluster flicking monitoring methods were compared. Trapping gave a time-averaged in- dication of thrips numbers, but numbers are probably affected by location of the trap and flow- ering stage of the apple. The beating tray method was the most versatile. It could be used re- gardless of flower condition and produced instant results. The currently recommended flower cluster flicking method produced few thrips and is affected by condition and age of the flowers, as well as time of day. We conclude that it is an ineffective method. Monitoring thrips numbers after blossom using a beating tray may give more practical economic thresholds for treatment. Key words: thrips, apples, Frankliniella occidentalis INTRODUCTION Western flower thrips (Frankliniella occidentalis (Pergande)) are small (1-2 mm) slender in- sects that feed on the flowers of many plants. They can cause damage on stone fruit by rasping the surface of the fruit as they feed. The main damage on apples is from females ovipositing in the young fruitlets, just after petal fall. The resulting puncture causes “pansy spot’, a whitish area around the oviposition site. This damage shows up mainly in light skinned varieties such as Granny Smith, but can also be a problem in Rome Beauty and McIntosh (Flint 1991). Chemical control of thrips may not be required every year. If other plants are in flower at the same time, they may dilute the thrips population below damaging levels (Beers et al. 1993). Al- though the relationship between thrips population and fruit damage is unclear, the relationship can only be found by monitoring the thrips during critical periods. Once the relationship is found, monitoring will show if control is required. Many monitoring methods require field sam- ples to be taken and analyzed in the laboratory (Madsen et al. 1975). For most consultants this is not convenient, because growers need the results immediately. Most instant monitoring meth- ods involve either sampling individual flowers (DeGrandi-Hoffman et al. 1988, Terry & De- Grandi-Hoffman 1988, Beers et al. 1993), or the use of a beating tray as used for sampling pear psylla (N. Simone personal communication). The objectives of this study were to compare different sampling methods and times and to evaluate colored sticky board traps. We also assessed thrips damage in the fruit. MATERIALS AND METHODS The ‘Granny Smith’ apple orchards used had either a previous history of thrips pests, or blocks where thrips had been found during flowering. They were at Moxee, Zillah, Prosser, Pasco (Sagemoor) and Mattawa, WA. All orchards used conventional insecticide pest control programs, except for the Mattawa orchard which used organic controls. Three monitoring methods were examined. The first involved sampling individual flower clusters (Beers et al. 1993). Five clusters from five trees were picked and individually given three vigorous shakes (or ‘flicks’) into a white plastic cup and the total number of thrips recorded. 64 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Table 1 The effect of color and attractant on mean (n = 72) daily number of total thrips caught. Means with the same letter are not significantly different at p < 0.05 (log (x+1) transformation). Factor Daily trap catch Colour blue 41.3a white 34.9b yellow 10.6c Attractant p-anisaldehyde 33.4a nicotinate 27.9ab none 25.4b- In the second method thrips were sampled by jarring them from a limb onto a white cloth tray and counting them. A 46 cm (18”’) square cloth beating tray was held under a nearly horizontal section of limb % to 1% inch in diameter with an average complement of flower clusters. The limb was tapped firmly three times with a 1-foot length of rubber hose. Twenty-five randomly selected sites on 25 trees were sampled throughout the block and the total number of thrips recorded. The third method used blue, white and yellow colored sticky traps. Also, Teulon et al. (1993) mentioned trap catch enhancement with the use of chemical attractants. We looked at both color and attractants as a sub-study within this evaluation. The traps were 10 x 15 cm Chroma line card traps produced by Phero Tech Inc., 7572 Progress Way. Ladner, B.C. Three colors were ex- amined: non U.V. white (No. 201); bright blue (No. 411); and bright yellow (No. 611). A chem- ical attractant, either p-anisaldehyde or nicotinic acid ethyl ester (Sigma Chemicals, POB 14508, St. Louis, MO) were each sprayed on 112 different cards. Each attractant was mixed as a 40% solution in 95% ethanol as described in Teulon et al. (1993). The control was 95% ethanol. Attractants were applied to both sides of card traps using one ‘squirt’ (emitting 0.8 ml) per side from a plastic spray bottle, held about 10 cm away. Traps were hung within foliage at about two-thirds of the height of the tree ( between 1.0 and 1.8 m) . At each sub block three blue traps, three blue traps treated with p-anisaldehyde, three blue traps treated with nicotinic, three white traps, three white traps treated with p-anisaldehyde, three white traps treated with nicotinic, three yellow traps, three yellow traps treated with p-anisaldehyde and three yellow traps treated with nicotinic were hung on trees. Trees were selected randomly and traps placed randomly. After a period of 3-5 days the numbers of all vis- ible thrips (all life stages and both sexes) were recorded and new traps randomly placed. Damage was assessed on 6 July at Sagemoor, Mattawa and Moxee and 12 July at Zillah. One hundred fruit were examined on five trees in each sub-block, and the number with one or more pansy spots was recorded. Data from the effect of color and chemical attractants on trap catch study, were transformed using log (x+1) and analyzed using General Linear Model in SAS. Site and time were included as factors. RESULTS AND DISCUSSION During the 1994 blossom season, relatively few thrips were found in south central Washing- ton. In some orchards that previously had a thrips problem, none could be found during blos- som. The orchard in Prosser and one in Zillah were dropped from the study due to a lack of thrips. In two of the orchards (Sagemoor and Mattawa), thrips were found relatively late in the flowering period. At Sagemoor the traps were not replaced after counting on 18 April. The number of thrips caught during the 18-20 April period in Table 3 was obtained by subtracting the number caught in the 13-18 April period from the 20 April total. These data were not used in the analysis of variance in Table 1. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 65 Blue caught more thrips than white and white more than yellow and the effect of color was significant at the p < 0.001 level (Table 1). The attractant p-anisaldehyde caught significantly (p < 0.05) more thrips than the check (Table 1). There was no significant differences between blue (the most attractive color) and attractants (Table 2). Table 3 shows the relative numbers found using the three methods. Traps collected the most thrips but the beating tray method gave immediate results. The Sagemoor Road orchard was monitored for the longest period and showed a rapid in- crease in thrips population (the beating tray method yielded 1 thrips on the first visit which rose to an average of 91 only one week later). The population later declined as expected (DeGrandi- Hoffman et al. 1988). Traps caught steadily increasing numbers of thrips over the whole period. The flower flick method at Sagemoor produced numbers that correlated with the beating tray method, but after petal fall is no longer a viable method since there are no flowers. At Moxee, more thrips were collected using the flower flick method compared to other meth- ods than at Sagemoor. This may be because trees at Sagemoor had more flowers per unit of limb than those at Moxee. The blue traps caught proportionately fewer thrips at Moxee than the other orchards, possibly because of the low flower and limb density, or the increased competition from a greater number of open flowers. As at Sagemoor, the late stage of flowering at Mattawa caused the traps to catch proportionately more thrips than the beating method. Table 4 shows little difference in damaged fruit between the orchard blocks. The orchard at Zillah, while having no thrips present during flowering , had similar damage to the other blocks. The best color for catching western flower thrips is still controversial. Even studies by one group of researchers can produce conflicting results. For example, Yudin et al. (1987) suggested white was the best color, yet one of their experiments showed blue catching the most. Our re- sults support Moffit (1964), that white was far superior to yellow, but he did not test blue. We showed that white is superior to yellow, contrary to the statements of the manufacturers (Phero Tech, personal communication). Blue caught more thrips than white and it was easier to see the thrips and to locate the traps in an orchard full of white blossom where white traps were partic- ularly difficult to find. These conflicting results may be due to subtle differences in the spectral qualities of the colors used and possibly to differences in the thrips population. Thrips in dif- ferent areas or at different times of the year may move to flowers of different colors. We did not see the 2-6 fold increase through the use of attractants that Teulon et al. (1993) found after applying anisaldehyde to sticky traps. This may be due to several factors. They used yellow traps, which are seldom the most attractive color. Our method of applying attractant dif- fered from theirs, although we applied more attractant than them. Our study was conducted in the windy conditions of the field, while they conducted theirs in greenhouses, where it may be easier for thrips to fly towards an odor gradient. Wind would release more volatile attractants from the surface, while at the same time diluting its atmospheric concentration (Van der Kraan & Ebbers 1990). Anisaldehyde also formed yellow clusters of crystals on the surface of the sticky board, a possible reaction with the solvents used, and this may have reduced the ‘sticki- ness’ of the trap as well as diluting the effect of the attractant. Attractants produced little benefit considering the effort required to apply them. Both attrac- tants were skin irritants and the spray drift reddened arms and hands when they were applied. There was also more than one anisaldehyde spill, making travel an unpleasant olfactory expe- rience. Yudin et al. (1987) discussed attractive traps and found good correlation between numbers caught in contrasting colored traps and the thrips population in lettuce crops. We had no absolute method of determining population, but we considered that the beating tray most consistently in- dicated population levels. This method sampled a unit of branch area, and while this varied from orchard to orchard as tree management varied, it did not change in a single orchard over the sampling period. Variation between orchards, might make economic thresholds difficult to determine. Compared with the results of the beating tray, the traps became more attractive near the end of flowering. This is probably when more thrips were leaving the apple trees. Traps give a time- averaged population estimate, since they ‘smooth’ variations of activity during and between 66 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Table 2 The effect of attractants on daily total number of thrips caught in different colored traps. Means with the same letter for the same color trap are not significantly different at p < 0.05 (log (x+1) transformation). Treatment Blue White Yellow Treated with p-anisaldehyde 41.8a 45.4a 13.6a Treated with nicotinate 41.9a 34.4b T3D Untreated 40.1a 13.6c 10.8ab Table 3 Comparison of thrips monitoring methods for ‘Granny Smith’ apple blocks, at three Washington orchards. Block Date Blossom! Flower Flick? Beating Tray? — Blue Traps* Sagemoor — Both 13 Apr 35% PF I 1] _ Sagemoor — E 18 Apr 60% PF 3) 33 — Sagemoor — W 18 Apr 55% PF a 38 -- Sagemoor — E 20 Apr 70% PF 24 82 73 Sagemoor — W 20 Apr 60% PF 10 We 108 Sagemoor — E 25 Apr 99% PF NF 3] 129 Sagemoor — W 25 Apr 95%. PF NF 51 87 Moxee — Both 22 Apr Full Bioom 9 30 _ Moxee — NW 26 Apr 20% PF 2) 85 4] Moxee — SE 26 Apr 20% PF 1] 69 3y Mattawa — NE 22 Apr 99% PF NF 30 164 Mattawa — SW 22 Apr 99% PF NF 49 129 1 PF = Petal Fall, NF = No Flowers 2 Flower flick method, total number of thrips found after flicking 25 flower clusters into a white paper cup. 3 Limb tapping method, total number of thrips found after 25 beating tray observations following three limb hits. 4 Blue trap method, daily average of total thrips caught in all nine blue traps. — nocollection Table 4 Incidence of Pansy spot in samples of 500 fruit from ‘Granny Smith’ orchard blocks Block Pansy Spot Sagemoor — E 2.4% Sagemoor — W 227% Moxee — NW 2.6% Moxee — SE 2.0% Mattawa —- NE 4.0% Mattawa — SW 1.6% Zillah 2.0% J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 67 days. The catch may also be affected by density of flowers around each trap. Position may also affect the catch, and we noticed that traps in sunny positions caught more than those in the shade. These factors also make comparisons between different orchards difficult. Madsen & Jack (1966) suggested that post petal-fall is the best time to spray for thrips, so monitoring at that time may give the best prediction of damage. The number of thrips caught may be related to number of flowers (or fruitlets) on a limb, which may make determining eco- nomic thresholds difficult. Beers et al. (1993) suggested that flower flicking should only be done in the late morning since thrips may only be on the flowers then. The beating tray method is not affected by this movement as the thrips probably only move on to neighboring leaves and branches. The beating tray method seemed to be the easiest and quickest and because it was probably not affected by time of day consultants could visit several orchards in a day. The flower flick method yielded few thrips, and is affected by time of day (Beers et al. 1993). Consultants would therefore be at orchards only between 10.am and noon. The method can not be used once flowering is finished, even though it does give an actual number of thrips per flower, which may give a good estimate of potential damage. Late in the flowering period, flower flicks could yield abnormally high numbers because all thrips might be on the last re- maining flowers. Hence flower flicks may not truly reflect relative risk of apple damage from the next generation of thrips. Madsen et al. (1975) used 20 thrips per 100 clusters (using a glass cylinder thrips extractor) as a treatment threshold, but found it did not keep damage below an acceptable level. Terry & DeGrandi-Hoffman (1988) found flower flicking less efficient than laboratory extraction methods, especially late in the blossom period. Numbers given by this method depend greatly on flower stage. Damage to the apples was similar in all orchards. Terry (1991) found that oviposition (dur- ing flowering) did not increase significantly with the number of thrips, hence monitoring by any method may not be particularly useful. Terry’s study ceased soon after petal fall. This is not the time of fruit damage but later in the season (as suggested by Madsen & Jack 1966). Further work is needed to determine if the beating tray method gives consistent results at any time of day as we suspect it should. Monitoring populations during the flowering season and af- ter flowering to see when thrips are in the trees would be useful to see if their presence later in the season can be related to damage. Populations of thrips were low in 1994. Other years might have high thrips numbers during flowering which could require preventative control at that time. Monitoring populations in more orchards during peak blossom and a few days after-petal fall, followed by an assessment of damage should indicate any correlation between numbers and damage. ACKNOWLEDGEMENTS We thank the Washington State Fruit Tree Research Commission for funding this study and Nana Simon for her help. REFERENCES Beers, E. H., J. F Brunner, M. J. Willet & G.M. Warner (eds). 1993. Western flower thrips. p125-127 in Orchard Pest Management: A resource book for the Pacific Northwest. 276pp. Good Fruit Grower, Yakima, Washington DeGrandi-Hoffman, G., L. I. Terry & R. T. Huber. 1988. Incorporating fruit set estimates with thrips management to create a decision support system for apples. HortScience 23: 571-574 Flint, M. L. (ed.). 1991. Thrips. p146 in Integrated Pest Management for apples and pears. 214pp. University of Cali- fornia, Davis, California Madsen, H. F. & I. D. Jack. 1966. The relation of thrips and pansy spot on apples. Can. Entomol. 98: 903-908 Madsen, H. F., H. F. Peters & J. M. Vakenti. 1975. Pest management: Experience in six British Columbia apple orchards. Can. Entomol. 107: 873-877 Moffit, H. R. 1964. A color preference of the western flower thrips, Frankliniella occidentalis. J. Econ. Entomol. 57: 604-605 SAS 1988. SAS Technical Report P-179, Additional SAS/STAT Procedures, Release 6.03, SAS Institute, Cary, NC: Terry, L. I. 1991. Frankliniella occidentalis (Thysanoptera: Thripidae) oviposition in apple buds: Role of bloom state, blossom phenology, and population density. Environ. Entomol. 20: 1568-1576 68 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 Terry, L. I., & G. DeGrandi-Hoffman. 1988. Monitoring western flower thrips (Thysanoptera: Thripidae) in ‘Granny Smith’ apple blossom clusters. Can. Entomol. 120: 1003-1016 Teulon, D. A. J.,D.R. Penman & P. M. J. Ramakers. 1993. Volatile chemicals for thrips (Thysanoptera: Thripidae) host finding and applications for thrips pest management. J. Econ. Entomol. 86: 1405-1415 Van der Kraan, C. & A. Ebbers. 1990. Release rates of tetradecenlol acetates from polymeric formulations in relation to temperature and air velocity. J. Chem. Ecol. 16: 1041-1058 Yudin, L. S., W. C. Mitchell & J. J. Cho. 1987. Color preference of thrips (Thysanoptera: Thripidae) with reference to aphids (Homoptera: Aphididae) and leafminers in Hawaiian lettuce farms. J. Econ. Entomol. 80: 51-55 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 69 An occurrence of two exotic ant (Formicidae) species in British Columbia KEN NAUMANN DEPT. BIOLOGY, LANGARA COLLEGE, 100 W. 49 AVE., VANCOUVER, B.C. VS5Y 2Z6 ABSTRACT Specimens of two exotic ant species, Wasmannia auropunctata Roger and Parathrechina longi- cornis Emery were found in an indoor tropical rainforest exhibit in Vancouver. Both species have spread far from their historical ranges to become established in tropical and subtropical ar- eas around the world, and are occassionally found in greenhouses and other protected areas in temperate regions. Key words: ants, exotic, habitat, indoor, British Columbia DISCUSSION Several species of tropical ants, because of the small size of the workers, polyphagous eating habits, and their ability to nest in a variety of situations, have become associated with human ac- tivities in regions far beyond their original ranges. Their ability to nest and feed within buildings allows them to live in much colder climates than would ordinarily be expected, and often causes them to be pests. They are sometimes called tramp species because of their tendency to hitch rides to new locations and to feed on spilled or unprotected human food. In January, 1994, specimens of two such ant species, Wasmannia auropunctata Roger (Myrmicinae) and Paratrechina longi- cornis Emery (Formicinae), were collected from within the tropical rainforest exhibit at the Van- couver Aquarium. | W. auropunctata, commonly called the little fire ant, is an aggressive, neotropical species. It is sensitive to cold temperatures and has become established in Mexico, south Florida (Spencer 1941) and California (Smith 1979), as well as other sub-tropical and tropical areas around the world. It is not a close relative of the imported red fire ant, Solenopsis invicta Buren, another neotropical species which has become a pest through much of the southern United States. W. auropunctata workers are small, 1.5—2 mm long, and yellow. Members of the genus can be identified by 11—segmented antennae (terminating in a 3—segmented club), 2 obvious spines pro- truding from the propodeum (posterior end of the alitrunk), and frontal carinae (raised ridges on the frons) that extend posteriorly past the eyes so as to form the lateral boundaries of grooves (scrobes) into which the first segments of the antennae can be folded. There are five mandibular teeth, and the large head is much broader than the thorax (Hdlldobler and Wilson 1990; Ulloa—Chacon and Cherix 1990). Little fire ants do not construct their own nests but use sheltered locations including rotten wood, covered soil, and plant cavities. The nests are diffuse and inconspicuous and often aggre- gate to form large, polygyne nests. Workers are polyphagous and opportunistic feeders that prefer to collect honeydew from aphids, hunt a wide variety of prey, or collect plant material. They are attracted to fatty and oily household foods, and dirty and sweaty clothing, but not sweets. Work- ers have a sometimes—painful sting but generally sting only when trapped between the body and clothing or some object. They have been a pest in citrus orchards, where they sting pickers, and have been reported to drive out less aggressive ant species and to cause an imbalance in phy- tophagous insect communities in a number of crops by defending honeydew—producing insects from predators and parasites (Thompson 1990; Ulloa—Chacon and Cherix 1990). At the Vancouver Aquarium, large numbers of little fire ants were found throughout the Gra- ham Amazon exhibit, where they formed numerous foraging trails along the edges of walls and floors, along the undersides of walkways, and up the trunks of plants. In the larger foraging trails, I observed up to 60 individuals passing a given point in both directions, each minute. The ants were found tending scale insects, and were most apparent on those plants (e.g., Amazon lily, Eucharis) that hosted scales. Up to several hundred of the tiny ants could be found, together with the scales, on the undersides of individual lily leaves. Nests were apparently contained within cracks in large 70 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 cement “rocks” contained within the display, and in walls separating the display from various fish tanks. The nests were not examined. W. auropunctata 1s occasionally found in greenhouses far from its endemic and naturalized ranges. As early as 1907, it was well established at Kew Gardens in London (Ulloa—Chacon and Cherix 1990), and Ayre (1977) reported it from Assiniboine Park, Winnipeg, MB, where it was the most numerous of several ant species in the greenhouse area of the tropical house. It is likely that it was introduced to the display at the Aquarium in plant material, associated soil, or both. The hot and humid conditions within the tropical display have recreated the ideal habitat for this species, but it is unlikely that it could become locally established elsewhere, except in such greenhouse en- vironments. Although little fire ants do occasionally sting Aquarium staff, they are not a problem for visitors, and probably go unnoticed because of their small size. Paratrechina longicornis workers are monomorphic, brown-black with bluish reflections, and approximately 2.5 mm long. There is a single reduced segment (petiole) between the alitrunk and the gaster, and it is somewhat rounded, rather than scale—shaped as in all the native British Co- lumbia species of the subfamily Formicinae. The antennae and legs are unusually long, and there are long, spiny hairs on the gaster and running in 2 rows down the alitrunk. Workers have no sting and do not bite. They are rapid runners, and sometimes show jerky, erratic movements (Thomp- son 1990). These ants may have originated in the Orient, although in North America they are now abun- dant in Florida and the Gulf States (Trager 1984). In more temperate areas they seek refuge indoors to survive cold winters (Smith 1965); they are commonly found indoors in New York city (Creighton 1950). Nests of another member of this genus, P. fulva Mayr, have been found in the tropical house at Assiniboine Park, Winnipeg, MB (Ayre 1977). P. longicornis will nest in trash, plant cavities, rotten wood, soil, or small crevices, and seek food throughout a building. They tend honeydew producers, and will also eat other insects, seeds, meats, greases, and sweets (Smith 1965). Colonies may contain up to 2,000 workers and 40 queens. Only two P. longicornis foragers were found within the tropical display at the aquarium. The relative lack of abundance is not surprising in the face of the aggressive nature and large numbers of W. auropunctata in that area. It is possible that P. Jongicornis nests were located elsewhere in the aquarium complex, and only a small number of workers were foraging in the tropical display. The presence of this species represents little or no problem at the aquarium because of its lack of sting or bite, and small numbers. ACKNOWLEDGMENTS The presence of an unusual ant was brought to my attention by W. Stephen of the Vancouver City Parks Board. M. S. Graham, T.H. Herbert, J. Rawle, and A. C. Short of the Vancouver Pub- lic Aquarium generously provided access and encouragement for studying and collecting the ants. Prof. M.B. Isman provided study facilities, and he and N. Brard reviewed a copy of the manuscript. REFERENCES Ayre, G.L. 1977. Exotic ants in Winnipeg. Manit. Entomol. 11:41—44. Creighton, W.S. 1950. The ants of North America. Bull. Mus. Comp. Zool. Harvard Univ. 104:1-585. Holldobler, B. and E.O. Wilson. 1990. The Ants. The Belknap Press of Harvard University Press. Cambridge, Mass. 732 pp. Smith, D.R. 1979. Formicoidea. In Catalog of Hymenoptera in America North of Mexico. Vol. 2. Smithsonian Insti- tute Press. Washington, D.C. pp 1323-1867. Smith, M.R. 1965. House-—infesting ants of the eastern United States. Their recognition, biology and economic impor- tance. U.S.D.A. Tech. Bull. 1326. 105 pp. Spencer, H. 1941. The small fire ant, Wasmannia in citrus groves—a preliminary report. Fla. Entomol. 24:6—14. Thompson, C.R. 1990. Ants that have pest status in the United States. Jn Applied Myrmecology. A World Perspective. Vander Meer, R., K. Jaffe and A. Cedeno ed.’s. Westview Press, Boulder, San Francisco, and Oxford. pp 51-67. Trager, J.C. 1984. A revision of the genus Paratrechina (Hymenoptera: Formicidae) of the continental United States. Sociobiology 9:49-162. Ulloa—Chacon, P. and D. Cherix. 1990. The little fire ant, Wasmannia auropunctata (R.) (Hymenoptera: Formicidae). In Applied Myrmecology. A World Perspective. Vander Meer, R., K. Jaffe and A. Cedeno eds. Westview Press, Boulder, San Francisco, and Oxford. pp 281-289. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 nl An unusually large aggregation of the western conifer seed bug, Leptoglossus occidentalis (Hemiptera: Coreidae), in a man-made structure S. E. BLATT DEPARTMENT OF BIOLOGICAL SCIENCES, CENTRE FOR PEST MANAGEMENT SIMON FRASER UNIVERSITY, BURNABY, BC, V5A 186 CANADA ABSTRACT An overwintering aggregation of more than 2000 Leptoglossus occidentalis is reported in a manufacturing plant in the southern interior of British Columbia. Such aggregations may be me- diated by pheromones. Range extension may have occurred through inadvertent transport of ag- gregations of overwintering adults. DISCUSSION The western conifer seed bug, Leptoglossus occidentalis Heidemann, is a serious pest of conifer seed production (Koerber 1963), particularly on Pinus spp. (Connelly and Schowalter 1991). During the fall adults, like other coreids, seek sheltered overwintering sites. When hu- ~ man habitation interfaces with forests, these sites can include garages, birds’ nests (Hussey 1953) and houses (T.W. Koerber, Entomological Services Inc., Berkeley, California, personal communication). L. occidentalis has recently extended the eastern limits of its range and has be- come acommon household pest in Michigan (Gall 1992), Ontario (Marshall 1991; McPherson etal. 1990), Wisconsin and Minnesota (Katovich and Kulman 1987). Numbers of insects found in or on the homes varied from less than a dozen to roughly a hundred individuals. , In October 1993, Richard Prebble, Manager of the Imperial Chemical Industries (ICI) Ex- plosives Plant in Tappen, BC, 78 km east of Kamloops, reported an infestation of L. occiden- talis in and around the manufacturing plant. On inspecting the site, I found large numbers of L. occidentalis congregated around door jambs, windows and in cracks within the concrete walls. Hundreds of bugs were aggregated around heating exhaust ports. I collected 1065 live bugs (608 males and 457 females) and estimated that there were at least 1000 more dead on the floors, win- dow sills and in the door jambs; a result of chemical control by the plant staff. Several workers indicated that the infestation was ‘manageable’ compared with what it had been just two weeks before. For the past three years, similar infestations have been observed at this plant; they re- portedly last for roughly three weeks and then ‘disappear’. An aerial photograph obtained from the BC Ministry of Forests showed that L. occidentalis must have flown a considerable distance to reach the aggregation site. The plant is located in a meadow, at least 300 m from forest edges to the north and west, 900 m from a patch of conifers to the east and 750 m from a small patch of conifers to the south. Small aggregations of Leptoglossus corculus (Say) have been observed in the southern USA (J.C. Nord, USDA Forest Service, Athens, Georgia, personal communication) and overwinter- ing aggregations of other Hemiptera also occur. Schowalter (1986) documented an aggregation of ca. 8,000 boxelder bugs, Boisea rubrolineata (Barber), in western Oregon. The aggregation was found 500-1,000 m away from feeding hosts. Aggregations of > 6,000 swallow bugs, Oe- clacus vicarius Horvath, have been reported in Washington (Zack 1990). Chinch bugs, Blissus leucopterus leucopterus (Say), also aggregate to overwinter in groups of typically < 200 indi- viduals (Negron and Riley 1991). In all instances, pheromonal attraction was suggested as a causal factor of aggregations. It has been hypothesized that extension in the range of L. occi- dentalis has occurred through the inadvertent transport by mankind of aggregations of bugs overwintering on or in transported goods (L.M. Humble, Canadian Forest Service, Pacific Forestry Centre, Victoria, BC, personal communication). 72 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 ACKNOWLEDGMENTS I thank Dr. J.-H. Borden for review and R. Prebble for allowing me to collect bugs on ICI premises. Funding for this work was provided by the Canadian Forest Service and Natural Sci- ences and Engineering Research Council of Canada. REFERENCES Connelly, A.E. and T.D. Schowalter 1991. Seed losses to feeding by Leptoglossus occidentalis (Heteroptera: Coreidae) during two periods of second year conedevelopment in Western White Pine. J. Econ. Entomol. 83:1485- 1486. Gall, W.K. 1992. Further eastern range extension and host records for Leptoglossus occidentalis (Heteroptera: Corei- dae): well-documented dispersal of a household nuisance. Great Lakes Entomol. 25:159-171. Hussey, R.F. 1953. Concerning some North American Coreidae (Hemiptera). Bull. Brooklyn Entomol. Soc. 48:29-34. Katovich, S.A. and H.M. Kulman 1987. Leptoglossus corculus and Leptoglossus occidentalis (Hemiptera:Coreidae) at- tacking red pine, Pinus resinosa, cones in Wisconsin and Minnesota. Great Lakes Entomol. 20: 119-120. Koerber, T.W. 1963. Leptoglossus occidentalis (Hemiptera: Coreidae) a newly discovered pest of coniferous seed. Ann. Entomol. Soc. Amer. 56:229-234. Marshall, S.A. 1991. A new Ontario record of a seed eating bug (Hemiptera: Coreidae) and other examples of the role of regional insect collections in tracking changes to Ontario’s fauna. Proc. Entomol. Soc. On. 122:109-111. McPherson, J.E., R.J. Packauskas, S.J. Taylor and M.F. O’Brien 1990. Eastern range extension of Leptoglossus occi- ~ dentalis with a key to Leptoglossus species of America north of Mexico (Heteroptera: Coreidae). Great Lakes En- tomol. 23:99-104. Negron, J.F. and T.J. Riley 1991. Seasonal migraton and overwintering of the chinch bug (Hemiptera: Lygaeidae) in Louisiana. J. Econ. Entomol. 84: 1681-1685. Zack, R.S. 1990. Swallow bug (Heteroptera: Cimicidae) in Washington with an unusual overwintering site. Pan Pac. Entomol. 66:25 1-252. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 73 Parasitoids of blackheaded fireworm (Rhopobota naevana Hbn.) larvae on cranberries, and larval escape behaviour SHEILA M. FITZPATRICK, JAMES T. TROUBRIDGE and CELINE MAURICE PACIFIC AGRICULTURE RESEARCH CENTRE, AGRICULTURE AND AGRI-FOOD CANADA 6660 N.W. MARINE DRIVE, VANCOUVER, B.C. V6T 1X2 ABSTRACT The parasitoids Hemisturmia tortricis (Coq.) (Tachinidae), Sympiesis bimaculatipennis (Gi- rault) (Eulophidae) and one male of the genus Microplitis (Braconidae) were reared from black- headed fireworm larvae collected on a cranberry farm in the Fraser Valley, B.C. Fireworm lar- vae escape Ovipositing parasitoid females by dropping from an “escape hatch” hole cut in the bottom of the feeding shelter. Key words: Vaccinium macrocarpon, Hemisturmia tortricis, Sympiesis bimaculatipennis, Mi- croplitis, Tortricidae, biological control, behaviour DISCUSSION The blackheaded fireworm of cranberry, Rhopobota naevana Hbn. (Lepidoptera: Tortricidae) is an economically important pest for which biological and other non-chemical control mea- sures are currently being sought. Two indigenous parasitoids, Trichogramma minutum Riley and T. sp. nr. sibericum Sorokina, are known to parasitize blackheaded fireworm eggs (Li et al., 1993), and a granulosis virus is associated with larval mortality in the field (Fitzpatrick and Theilmann, unpublished data). Spiders of the genus Pardosa, Xysticus and Tibellus have been found preying upon fireworm moths in field cages (Fitzpatrick and Troubridge, 1993) and la- dybird beetles, Coccinella californica Mann., have been observed feeding on fireworm larvae in the field (Plank, 1922). However, except for Plank’s (1922) report that “numerous very small wasplike insects ... can be seen flying over the tops of the vines on badly infested bogs’, there are no records of parasitoids attacking larvae. In 1991, we collected ca. 200 blackheaded fireworm larvae from a cranberry farm in Pitt Meadows, B.C. that was seldom treated with insecticide. From these larvae, six parasitoids be- longing to three species emerged. Two were Hemisturmia tortricis (Coq.), a tachinid fly known to parasitize nine other leafroller species as well as larvae in the moth families Glyphipterygi- dae, Nymphalidae, Oleuthreutidae, Pterophoridae and Pyralidae (Amand, 1978). Three para- sitoids were Sympiesis bimaculatipennis (Girault), an eulophid wasp that attacks leafrollers but is reported to prefer blotchmining or skeletonizing lepidopterans (Krombein, 1979). The sixth parasitoid was a male of the genus Microplitis (Hymenoptera:Braconidae) that could not be keyed further because males of this genus cannot be identified to species (M. Sharkey, C.L.B.R.R., Ottawa, personal communication). Blackheaded fireworm larvae feed at the tips of cranberry runners or upright shoots, although newly hatched first instars may mine into the underside of the leaf on which they hatch if no new growth is available (Plank, 1922). A larva webs three to five of the top leaves together and, pro- tected within this “tent”, feeds on new leaves and leaf primordia. We have observed female S. bimaculatipennis walking over the tents, tapping with their antennae and probing between leaf edges with their ovipositor. Although we have not observed the host-seeking behaviour of H. tortricis, other members of its tribe (Winthemiini) lay eggs directly on the host, so it too must somehow locate larvae within tents (D.M. Wood, personal communication). We have seen la- dybird beetle larvae attempting to pry tents open using their legs and mandibles. However, entry into a tent does not guarantee success for a parasitoid or predator, because the larva often drops on a silken thread through an “escape hatch” hole previously cut in the bottom of the tent. Larvae also use the holes to leave tents depleted of food. Holes range in size from 74 J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 approx. 0.5 mm by 0.7 mm (made by early instars) to 4.6 mm by 1 mm (made by late instars). Larvae have been seen returning to tents from which they have previously escaped. The tiny, leaf-mining first instars may also be subject to parasitism by S. bimaculatipennis, although this remains to be demonstrated or observed. ACKNOWLEDGEMENTS We thank Drs. B. E. Cooper, J. Huber and M. Sharkey at the Centre for Land and Biological Resources Research in Ottawa for identifying the parasitoids. We are also grateful to Sharon Clements, Dr. R. S. Vernon and two anonymous reviewers for helpful comments on the manu- script. This study was supported by funding from Agriculture and Agri-Food Canada, the British Columbia Cranberry Growers Association and Ocean Spray Cranberries, Inc. REFERENCES Armand, P. H. Jr. 1978. A host-parasite catalog of North American Tachinidae. Misc. Pub. U.S. Dep. Agric. 1319: 278- 280. Fitzpatrick, S. M. and J. T. Troubridge. 1993. A modified live-trap for assessing mating disruption of Microlepidoptera. Can. Entomol. 125: 1135-1136. Li, S. Y., G. M. Sirois, A. Luczynski and D. E. Henderson. 1993. Indigenous Trichogramma (Hym.: Trichogrammati- dae) parasitizing eggs of Rhopobota naevana (Lep.: Tortricidae) on cranberries in British Columbia. Entomophaga 38: 313-315. Krombein, K. V. 1979. Catalog of Hymenoptera in America north of Mexico. Vol. 1: 970. Smithsonian Institute Press, Washington. Plank, H. K. 1992. The blackheaded fireworm of cranberry on the Pacific coast. Bull. U.S. Dep. Agric. 1032. J. ENTOMOL. Soc. BRIT. COLUMBIA 91, DECEMBER, 1994 75 NOTICE TO CONTRIBUTORS The Society has no support except from subscriptions. The page charge for articles has been set at $45.00 and includes all extras except coloured illustrations, provided that such extras do not comprise more than 40% of the published pages. Coloured illustrations will be charged directly to the author. Authors not attached to universities or official institutions who must pay these charges from their personal funds and are unable to do so, may apply for assistance when submit- ting a manuscript. Reprints are sold only in hundreds at the following prices: Number of pages 1-4 5-8 9-12 13-16 17-20 21-24 25-28 First 100 copies $55.00 78.00 108.00 137.00 174.00 217.00 264.00 Each extra 100 12.00 16.00 20.00 24.00 28.00 32.00 36.00 Discounts up to 50% may be granted to authors who certify at the time of ordering that they are buying reprints at personal expense. 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Belton, Editor. ) Recycled Paper x ri ‘ a ; t i f : % pint rp ry { Journal of the Entomological Society of British Columbia Volume 91 Issued December 1994 ISSN #007 1-0733 Directors of the Entomological Society of British Columbia, 1994—95 Gillespie, David R. and D.J.M. Quiring. Reproduction and longevity of the predatory mite, Phytoseiulus persimilis (Acari: Phytosetidae) and its prey, Tetranychus urticae (Acari: Tetranychidae) on different host plants Schaber, Burton D., Timothy J. Lysyk and Derek J. Lactin. Phenology of the alfalfa weevil (Coleoptera: Curculionidae) in alfalfa grown for seed in southern Alberta Cannings, Robert A. Robber flies (Diptera: Asilidae) new to Canada, British Columbia, Yukon and the Northwest Territories with notes on distribution and habitat Knight, Alan. Insect pest and natural enemy populations in paired organic and conventional apple orchards in the Yakima Valley, Washington Taylor, S.P. and R.D. Cozens. Limiting white pine weevil attacks by side and overstory shade in the Prince George Forest Region Mayer, D.F. Effects of male to female ratio and number of females per nesting tunnel on sex ratio and number of progeny of the alfalfa leafcutter bee Megachile rotundata (Hymenoptera: Megachilidae) Cossentine, J.E. and L.B. Jensen. The role of two eulophid parasitoids in populations of the leafminer, Phyllonorycter mespileila (Lepidoptera:Gracillariidae) in British Columbia Syed, A. Notes on the biology and rearing of the carrion fly Prochyliza brevicornis (Melander) (Diptera: Piophilidae) Wood, L., D.A. Raworth, and M. Mackauer. Biological control of the two-spotted spider mite in raspberries with the predator mite, Phytoseiulus persimilis Bradley, S.J. and D.F. Mayer. Evaluation of monitoring methods for western flower thrips, Frankliniella occidentalis (Thysanoptera: Thripidae), during the blossom period of ‘Granny Smith’ apples NOTES Naumann, Ken. An occurrence of two exotic ants (Formicidae) species in British Columbia Blatt, S.E. An unusually large aggregation of the western conifer seed bug, Leptoglossus occidentalis (Hemiptera: Coreidae), in a man-made structure Fitzpatrick, Sheila M., James T. Troubridge, and Celine Maurice. Parasitoids of blackheaded fireworm (Rhopobota naevana Hbn.) larvae on cranberries, and larval escape behaviour NOTICE TO CONTRIBUTORS E a J ournal of the Entomological Society of British Columbia Volume 92 Issued December 1995 ISSN #0071-0733 Blakbsk © LIBRARIES J S B & Entomological Society of British Columbia COVER : The symbol of the 1995 Annual General Meeting of the Entomological Societies of Canada and British Columbia is reproduced on this year’s cover. It is from a limited edition print, Frozen Mosquito by BC native artist, Michael Blackstock. He was — born in 1961 and is a status native with the Gitanmax Band in Hazelton, as well as a professional forester. He was inspired by the Tsimshian legend of the origin of the mosquito - in ancient times, blood sucking animals in human form used to invite travellers to their village and then drain their victims’ blood by stabbing their long crystal noses into the necks of the unsuspecting travellers while they slept. One young man awoke in time to save himself. He fled from the village with the chief in hot pursuit. The chief tracked the young man to a lake where he had hidden in a tree on the shore. The chief exhausted and soaked himself trying to attack the man’s reflection in the water and then, while recovering on the shore, froze solid. The young man and his people took the frozen chief and burned him to ashes. When the fire had burned out, a wind came up and blew the ashes into the air where they turned into clouds of mosquitoes. The photograph superimposed on the drawing was taken and scanned by the editor from a frozen female Culiseta incidens (Thomson) reared by David Onyabe. One of the Province’s commonest and largest species; it is magnified 7.5 times. The Journal of the Entomological Society of British Columbia is published annually in | December by the Society Copyright® 1995 by the Entomological Society of British Columbia Designed and typeset by Peter and E. M. Belton and David Holden. Printed by Reprographics, Simon Fraser University, Burnaby, B.C., Canada. Printed on. Recycled Paper. ® J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 1 Journal of the Entomological Society of British Columbia Volume 92 Issued December 1995 ISSN #007 1-0733 Directors of the Entomological Society of British Columbia 1995 - 1996............. 2 Kasana, A. and M.T. AliNiazee. Ovipositional preferences of the walnut husk fly, Rhagoletis completa (Diptera: Tephritidae) on various fruits, vegetables and varieties IBV HII creek tecist ed vari Ren er mach oat legs Lian ad ates whe o's ata Gee Oe ae eos ee 3 Horton, D.R., T.M. Lewis and T.J. Weissling. Reduction in feeding by diapausing and post diapause pear psylla (Homoptera: Psyllidae) caused by extract.from buffalo gourd MOOG UTO ACERS) tee ei 2 ton tebe eel ecaee w a eae Se aaa eee hee Mee aeie meat ae 9 Paulson, L.C. Monitoring and dynamics of a Dopuglas-fir beetle outbreak in Jasper. National Park, “Alberta... 25 cs bce ec bs een be ee ee ce dee te twa cae ees 17 Richmond, J.A., R.A. Werner and A.T. Drooz. Larch sawfly, Pristiphora erichsoni (Hymenoptera: Tenthredinidae) and its parasitoids from Alaska................. 25 Knight, A. The impact of codling moth (Lepidoptera: Tortricidae) mating disruption on apple pest management in Yakima Valley, Washington....................... 29 Alfaro, R.I. A sequential sampling system for the white pine weevil, Pissodes strobi ‘Coleoptera: Curculionidae). 2.0... 22... ok oo es be ee eat ou ew eee 39 Hunter, A.F. and B.S. Lindgren. Range of gypsy moth in British Columbia: a study of GlMHAliC SUMADINIY 25 oo a. ba Gale awe ee as kp bet AA eS Sos Sa 45 Danks, H.V. Regional diversity of insects in the Pacific Northwest................. 5 Xu, G. and G.E. Long. Feeding and performance of Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) reared on nightshade and potato........ 73 Taylor, S.P., B.S. Lindgren and J. Johnson. Detection of Pissodes strobi (Coleoptera: Curculionidae) using large-scale 70 mm colour photography................... 81 Troubridge, J.T. and L.G. Crabro. A new species of Copablepharon (Lepidoptera: Noctuidae) from British Columbia and Washington......................0.... 87 Kazak, C., W.W. Cone and L.C. Wright. The vertical distribution of mites and aphids on hops in southcentral Washington during the summer of 1993.................. sii Li, S.Y., S.M. Fitzpatrick and D.E. Henderson. Grooved board traps for monitoring the black vine weevil (Coleoptera: Curculionidae) in raspberry fields................ 97 Gray, T.G. and M.A. Hulme. Mating disruption of Douglas-fir tussock moth one and two years after the application of pheromone.....................0...0.000. 101 NOTE Eldredge, E.P. and C.R. Baird. First record of orange mint moth (Lepidoptera: Pyralidae) on commercial peppermint inIdaho.....................0..0000. 107 meaner TO CONTRIBUTORS, 2c. k lic eects cs fess eee ee estat ens 110 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 DIRECTORS OF THE ENTOMOLOGICAL SOCIETY OF BRITISH COLUMBIA FOR 1995-96 President Gail Anderson Simon Fraser University President-Elect Dave Gillespie Agriculture and AgriFood, Agassiz Past-President Linda Gilkeson B.C. Ministry of Environment, Victoria Secretary Robb Bennett Ministry of Forests, 7380 Puckle Rd., Saanichton, B.C. V8M 1W4 Treasurer Robb Bennett Editorial Committee (Journal) Peter Belton (Editor) H.R.MacCarthy Dave Raworth Editor (Boreus) E.M_Belton / Troy Danyk S.F.U. Directors D.Morewood (2nd) H-Philip (2nd) M-Smirle (2nd) E.Tomlin (1st) W.Strong (1st) Honorary Auditor Sheila Fitzpatrick Agriculture and AgniFood, Vancouver Regional Director of National Society Terry Shore Pacific Forestry Centre, Victona J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 3 Ovipositional preferences of the walnut husk fly, Rhagoletis completa (Diptera: Tephritidae) on various fruits, vegetables and varieties of walnuts ABDULMAJID KASANA and M. T. ALINIAZEE DEPARTMENT OF ENTOMOLOGY, OREGON STATE UNIVERSITY CORVALLIS, OREGON 97331 ABSTRACT The ovipositional preferences of the walnut husk fly, Rhagoletis completa, were studied using different fruits, vegetables, and walnut cultivars. Among the fruits and vegetables tested, pear was the substrate most often chosen for egg deposition, followed by nectarine, apple, green pepper, potato, and tomato. The eggs hatched equally well in all the substrates, but the larvae completed their growth and development only in nectarine. Among the varieties of walnuts tested, the most egg punctures per nut were in CVs 'Spurgeon' and 'Manregian' and the most eggs per nut were deposited in 'Manregian'. The females made the fewest egg punctures deposited the fewest eggs per nut in ‘Hartley’. Key words: Oviposition, development, walnut, walnut husk fly, Rhagoletis completa. INTRODUCTION Tephritid fruit flies have been cultured throughout the world for different research purposes, and have been reared from different hosts. Multivoltine tropical fruit flies are relatively easy to rear (Steiner and Mitchell 1966), whereas the univoltine temperate flies including the walnut husk fly (WHF), Rhagoletis completa Cresson (Diptera: Tephnitidae) are difficult to culture in the laboratory. Different techniques such as wax domes, gelatin balls, paraffin foam balls, and agar balls have been tried for oviposition, with varying degrees of success (Hagen ef al. 1963, Prokopy 1966, Haisch and Boller 1971). Foam rubber spheres of about 5 cm diam, wrapped in parafilm, were developed by Hagen as oviposition devices for the WHF (Cirio 1972). We have tested different artificial diets for rearing WHF larvae without much success; consequently, this insect has never been satisfactorily reared in the laboratory on artificial diets. Larval diet seems to be the major difficulty to continuous rearing. The WHF is a major pest of walnut, but has also been recorded from peaches and nectarines. We have found breeding populations of WHF from a peach orchard in Washington state, although such occurrences are rare. Differential susceptibility of walnut varieties to WHF was shown by Boyce (1934) in California. Reported here are the results of an ovipositional preference study dealing with different fruits, vegetables and selected varieties of walnuts. The larval development and survival in the different substrates is also reported. MATERIALS AND METHODS Different fruits and vegetables were tested including the ‘D'Anjou' pear (Pyrus communis), ‘Golden Delicious' apple (A/a/us domestica), 'Supreme' nectarine (Prunus 4 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 persica), ‘Pontiac’ red potato (Solanum tuberosum), ‘Jupiter Premarilla' green bell pepper (Capsicum annum), and ripe ‘Roma’ tomato (Lycopersicon esculentum) using a randomized complete block design to test for ovipositional preference. Adult WHF were maintained at 24+1° C, 80£10% RH and 16:8 L:D photoperiod. A diet consisting of a mixture of yeast hydrolysate, fructose (Nutritional Biochemicals Co., Cleveland, Ohio) and distilled water at a ratio 4:7:10 by weight, respectively, as described by Tsiropoulos (1978), was provided for adults. This diet and distilled water were offered to the flies continuously on sterile absorbent cotton. Twelve mated pairs of mature flies (18-20 days old) were confined in each of four wooden-frame cages (35x25x40 cm) containing one each of the six substrates described above. The flies were given 48 hr to oviposit. The experiments were repeated 4 times, and the substrates were examined for numbers of punctures, and eggs in each puncture. The data were analyzed using ANOVA and means were separated by Duncan's multiple range test (significant at p< 0.05). Substrates provided to the flies for egg laying were dissected to obtain eggs. One hundred eggs (<24 hr old) were removed randomly from each substrate and placed separately on moist filter paper in petri dishes, for each substrate. The petri dishes were placed in cardboard cartons and then transferred to a growth chamber at 24+1°C, and 80+10% RH. The eggs were examined daily until the 8th day after first hatch, then discarded. To determine the development of larvae in different substrates, oviposited substrates (four of each kind) with 1-2 oviposition punctures were placed in plastic containers (18.5x13x11 cm) (Tri-State Plastics, Dixon, NY) with sifted vermiculite in the bottom so that mature larvae could pupate. These containers were placed in a rearing room maintained at 24+1°C, 80£10% RH, and 16:8 L:D photoperiod, for larval development. Pupae collected from nectarines, were stored at 3°C for four months and then moved to a rearing room for adults to emerge. Eggs laid in apples in the laboratory were removed and surface sterilized in 0.01% sodium hypochlorite solution for 3 min, rinsed in 70% ethyl alcohol and then washed in distilled water (Neilson 1969, AliNiazee and Brown 1977). These eggs were then placed on wet filter paper in petri dishes and transferred to a growth chamber maintained at 24+1°C, and 80£10% RH for hatching. Newly hatched larvae were transferred with a fine camel hair brush to two different artificial diets developed for the closely-related larvae of the western cherry fruit fly, Rhagoletis indifferens (AliNiazee and Brown 1977) and the apple maggot, Rhagoletis pomonella (Neilson 1969) in 5 cm diam petri dishes and larval development was checked. To determine the oviposition of WHF on five walnut varieties, a randomized complete block design was used for the treatments, replicated four times. The experiment was set up in a rearing room maintained at 24+1°C, 80£10% RH, with a photoperiod 16:8 L:D. Nuts of varieties 'Franquette’, ‘Spurgeon’, 'Mayette'’, 'Manregian', and ‘Hartley’ were obtained from unsprayed orchards near Junction City, Oregon. They were thoroughly checked for oviposition punctures, and clean nuts with 5 cm twigs were placed in 35 mL plastic cups with water. One nut of each variety was hung in its cup in each of four wooden cages (35x25x40 cm). Five mated pairs of mature flies (18-20 days old) were released in each cage. Food and water were provided to flies as described. After 48 hr the nuts were examined for oviposition punctures, and eggs in the punctures. The data were analyzed using ANOVA and means were separated by Duncan's multiple range test (p <0.05). J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 5 RESULTS AND DISCUSSION The data (Table 1) show a significant (p <0.001) difference in ovipositional response of WHF to different fruits and vegetables provided for oviposition. The highest numbers of egg punctures per substrate were in pear (8.7+0.5, mean+SD), followed by nectarine (5.5+0.9), apple (3.0£0.4), green bell pepper (1.7+0.5), potato (1.2+0.2), and tomato (0.5+ 0.3). The number of eggs laid was also significantly different. The highest total number of eggs per substrate was laid in pear (227.5410.4, mean+SD) followed by nectarine (69.7+16.6), apple (37.748.6), pepper (17.043.7), potato (10.042.2), and tomato (5.5+3.28). The substrate with the highest number of punctures also had the most eggs and the substrate with the lowest number of punctures had the fewest eggs. Table 1 Ovipositional preferences of female Rhagoletis completa for various substrates in the laboratory. OVIPOSITIONAL PUNCTURES/ EGGS/ EGGS SUBSTRATE SUBSTRATE SUBSTRATE HATCHED MEAN + SD MEAN + SD (%) Pear 8.7+0.5a 227.5+10.4a 92 Nectarine 5.5+0.9b 69.7 +16.6 b 92 Apple 3.020.4¢ 37.748.9c 90 Pepper 1.7+0.5 cd 17.0 + 3.7 cd 84 Potato 1.2+0.2 de 10.0 + 2.2 cd 86 Tomato 0.5+0.3e 5.5+3.3e 88 Means in a column followed by different letters are significantly different (Duncan's multiple range test), p<0.05. Cirio (1972) reported that the female WHF probably selects an ovipositional substrate based on visual stimuli, such as color, shape, size, and other surface characteristics and to a certain extent on the internal humidity. It appears that pear must closely resemble walnuts in physical qualities to elicit such a high ovipositional response from WHF (Table 1). Although no walnuts were included in this trial for direct comparison, indirect comparison of data shown in Table 2, taken under the same conditions, suggests that more eggs were laid in pears than in walnuts. Eggs obtained from various substrates hatched on moist filter paper (Tablel), and there were few apparent differences. For example, about 92% of the eggs obtained from pears and nectarines hatched followed by 90% from apples, and 84% from green bell peppers. However, larval survival was not uniform. In potatoes, tomatoes and green peppers the larvae died soon after hatching, whereas in pear and apple, some larvae reached the second and even third instars but died before pupation. In nectarine the larvae pupated successfully. In an earlier study, Boyce (1934) had found peach to be a suitable host for this insect, while other fruits tested including naval orange, tangarine, grapefruit, apple, pear, grape, potato, egg plant, bell pepper and tomato were unsuitable. The WHF larvae did not develop on the artificial diets suitable for cherry fruit fly and apple maggot larvae, although some larvae moulted to the second and even third instars 6 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 but all died before pupation. These media might support larval development with some additional ingredients and changes. Unusual growth of mold on artificial diets may also have interfered with larval growth. Rhagoletis flies are well known for developing races specific to particular hosts (Bush 1969, Boller and Bush 1974). Bush (1969) speculated that the apple maggot developed different sympatric races as a result of shifts to unexploited hosts. The shift of apple maggot from its native host hawthorn (Crataegus spp.) to domestic apple (Malus domestica) in eastern North America over one hundred years ago, has now resulted in partial reproductive isolation for these two populations (Feder et al. 1988). McPherson et al. (1988a,b) found significant differences in allele frequencies between apple maggot fly populations raised on apple and hawthorn, and these siblings have been cited as example of sympatric speciation through divergence in host plant association (Bush 1969). Seasonal asynchrony caused by different fruit developing at different times is perhaps sufficient to initiate and maintain a restricted gene flow among different fly populations from different hosts thus leading to new host races (Smith 1988). Although no host race formation has been reported in R. completa, some genetic changes in different WHF populations collected from walnuts have already been reported by Berlocher (1984) as a result of the introduction of this species to different areas of the western United States. The data on varietal preference presented in Table 2 show that female flies made significantly (p<0.05) more punctures per nut in cultivars 'Spurgeon' and 'Manregian' and deposited the highest numbers of eggs in these two varieties. Significantly fewer eggs were deposited per nut in 'Mayette' and 'Franquette’. The fewest punctures and eggs were found in ‘Hartley’, which appeared to be highly resistant to oviposition. In a field study, Shelton and Anderson (1990) showed that 'Hartley' was much less susceptible to WHF attack than other varieties tested, including CVs 'Ashley', ‘Payne’, or 'Serr', over a 6-year study period in California. Table 2 Ovipositional preferences of female Rhagoletis completa for walnut varieties. PUNCTURES/NUT EGGS/NUT . EGGS/PUNCTURE VARIETY MEAN + SD MEAN + SD MEAN + SD Hartley 0.5+0.3a 4722 sa 952054 Mayette 10+0.0a 14°22 :7.)be 14.2+1.1be Franquette 10+0.0a 26.7'+ 5.3 cd 28.0+4.8d Spurgeon 3.2+0.2¢c 43.37 = 7/0:de 13.2 + 1.1 be Manregian 2.2+0.2b T0237 € 20.2 + 2.0 cd Means in a column followed by different letters are significantly different (Duncan's multiple range test), p<0.05. REFERENCES AliNiazee, M. T. and R. D. Brown. 1977. Laboratory rearing of the western cherry fruit fly, Rhagoletis indifferens (Diptera: Tephritidae) : oviposition and larval diets. Can. Entomol. 109:1227-1234. Berlocher, S. H. 1984. Genetic changes coinciding with the colonization of California by the walnut husk fly, Rhagoletis completa. Evolution. 38: 906-918. Boller, E. F. and G. L. Bush. 1974. Evidence for genetic variation in populations of the European cherry J. ENTOMOL. Soc. BRIT. COLUMBIA 92, DECEMBER, 1995 7 fruit fly, Rhagoletis cerasi (Diptera: Tephritidae) based on physiological and hybndization experiments. Entomol. exp. appl. 17: 279-293. Boyce, A. M. 1934. Bionomics of the walnut husk fly, R/iagoletis completa Cresson. Hilgardia. 8:363-579. Bush, G. L. 1969. Sympatric host race formation and speciation in frugivorous flies of the genus Rhagoletis (Diptera: Tephnitidae). Evolution. 23: 237-251. Cino, U. 1972. Osservazioni sul comportamento di ovidepositione della Rhagoletis completa Cresson (Diptera: Trypetidae) in laboratorio. Atti IX Congresso Nazionale Italiano di Entomologia 1972, pp. 99- 117. Feder, J. L., C. A. Chilcote and G. L. Bush. 1988. Genetic differentiation between sntene host races of the apple maggot fly Rhagoletis pomonella. Nature. 336: 61-64. Hagen, K. S., L. Santas, and A. Tsecouras. 1963. A technique of culturing the olive fly, Dacus oleae Gmel., on synthetic media under zenic conditions, pp. 333-356. Jn: Radiations and radioisotopes applied to insects of agricultural importance. Proc. Symp. Int. Atom. Energy Agency, Vienna. Haisch, A. and E. F. Boller. 1971. Genetic control of the European cherry fruit fly, Rhagoletis cerasi L. Progress report on rearing and sterilization, pp. 67-76. Jn: Sterility principle for insect control or eradication. Int. Atomic Energy Agency, Vienna. McPherson, B. A., D. C. Smith, and S. H. Berlocher. 1988a. Genetic differences between host races of Rhagoletis pomonella. Nature. 336: 64-66. McPherson, B. A., C. D. Jorgensen, and S. H. Berlocher. 1988b. Low genetic variability in Utah cherry infesting population of the apple maggot, Rhagoletis pomonella. Entomol. exp. appl. 46: 155-160. Neilson, W. T. A. 1969. Rearing larvae of the apple maggot on an artificial medium. J. Econ. Entomol. 62: 1028-1031. Prokopy, R. J. 1966. Artificial oviposition devices for apple maggot. J. Econ. Entomol. 59: 231-232. Shelton, M. D. and J. L. Anderson. 1990. Walnut cultivars: evidence for differential susceptibility to insect pests. Fruit Varieties J. 44(4): 179-182. Smith, D. C. 1988. Heritable divergence of Riragoletis pomonella host races by seasonal asynchrony. Nature. 336: 66-67. . Steiner, L. F. and S. Mitchell. 1966. Tephritid fruit flies, pp. 555-583. Jn: C. N. Smith (Ed.), Insect Colonization and Mass Production. Academic Press, New York. 618 pp. Tsiropoulos, G. J. 1978. Holidic diets and nutritional requirements for survival and reproduction of the walnut husk fly. J. Insect Physiol. 24: 239-242. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 9 Reduction in feeding by diapausing and postdiapause pear psylla (Homoptera: Psyllidae) caused by extract from buffalo gourd (Cucurbitaceae) DAVID R. HORTON, TAMERA M. LEWIS and THOMAS J. WEISSLING USDA-ARS 5230 KONNOWAC PASS RD. WAPATO WA 98951 ABSTRACT Rates of honeydew production were lower in diapausing winterform pear psylla, Cacopsylla pyricola (Foerster), than in psylla brought out of diapause by exposure either to long-day conditions or to an insect growth regulator (fenoxycarb). An extract obtained from a nonhost species, buffalo gourd (Cucurbita foetidissima HBK.), caused reduced honeydew production when misted onto pear shoots. Reductions in feeding were aS pronounced in diapausing insects as in psylla that were in a postdiapause condition. Ovanan development scores were positively correlated with honeydew production, indicating that feeding deterrents may be useful for delaying the onset of egglaying in the field. Key words: Insecta, Cacopsylla pyricola, diapause, honeydew production, feeding deterrent. INTRODUCTION Pear psylla, Cacopsylla pyricola (Foerster), is an important pest of commercial pears in both North America and Europe. The species is seasonally dimorphic, producing a large, dark overwintering form (winterform) in fall. This morphotype overwinters in a photoperiod-induced reproductive diapause, characterized by immature ovaries and a reduction or absence of mating (Krysan and Higbee 1990). Large numbers leave the pear orchard in fall to overwinter on nonhost species. Reentry into the orchard and egglaying begin in late winter. The winterform morphotype has been the focus of a great deal of research, both because control of this stage prevents problems later in the season (Westigard and Zwick 1972), and because aspects of its life history (especially diapause) may make it vulnerable to new control technologies (e.g., Krysan 1990). There is a complex relationship between diapause status of psylla and its host plants. Overwintering psylla require access to a moisture source (Kaloostian 1970, Hodgson and Mustafa 1984). A number of species, including pear, appear to satisfy this requirement (Horton et a/. 1994). The fact that many winterform psylla survive the winter outside of the pear orchard indicates that diapausing insects must be somewhat generalized feeders. Conversely, late postdiapause and reproductive insects are uncommon outside of the pear orchard. Thus, nonpear species may become less acceptable or unacceptable to pyslla coinciding with the end of diapause. We tested three hypotheses dealing with pear psylla diapause, feeding, and their interaction. We first tested whether feeding by winterform psylla is reduced in the presence of an extract obtained from a nonhost plant species. Secondly, we tested whether feeding rates are higher in postdiapause psylla than in diapausing psylla. One 10 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 common characteristic of diapause in other insects is a reduction in feeding (Tauber et al. 1986). Thirdly, we compared feeding rates of diapausing and postdiapause psylla in the presence and absence of a putative feeding deterrent, and hypothesized that the deterrent would have less effect on diapausing insects, due to their generalist feeding habits, than on postdiapause insects. MATERIALS AND METHODS Female winterform pear psylla were collected from commercial pear orchards near Yakima, WA on three dates: 14 Dec. 1993, 28 Dec. 1993, and 23 Nov. 1994. Psylla were exposed to one of three conditioning treatments designed either to maintain diapause or to end it: (a) control (short-day [10:14 L:D]); (6) long-day (16:8 L:D); (c) short-day; shoots misted with an insect growth regulator (fenoxycarb; obtained from Maag Agrochemicals, Vero Beach, FL). The insects were kept in three screened plastic cages (1 cage per conditioning treatment) containing dormant pear shoots from an unsprayed orchard; shoots had their cut ends placed in jars of water. Control (short-day) conditions maintain diapause, whereas both long-day conditions and contact with fenoxycarb break diapause (Krysan 1990). For the fenoxycarb treatment, the pear shoots were sprayed to runoff with fenoxycarb at the rate of 0.1 g [AI] per liter of tap water. Shoots were allowed to dry, and psylla were added to the cage. Psylla were conditioned for 1 week at 20°C in three separate environmental chambers (1 chamber per conditioning treatment). After seven days of conditioning, the feeding portion of the experiment was conducted. Conditioned psylla were moved to 135 ml screened feeding arenas, each arena containing a single cut shoot of dormant pear from an unsprayed orchard. The cut end of the shoot was kept in tap water. Four females from the same conditioning treatment were placed in each arena. There were 46-48 arenas per conditioning treatment (summed over the three collection dates). The insects were kept at room temperature (22°C) for the duration of the feeding trial. Half of the pear shoots for each conditioning treatment (N = 23-24) were misted to runoff with an extract known to cause reduced egglaying by psylla (Weissling unpublished data). The extract was made from the tap roots of buffalo gourd, Cucurbita foetidissina HBK., obtained in the summer of 1988 from plants growing near Parks, Nebraska. The plant material was air-dried and ground to a fine powder (60-80 mesh), and then stored at room temperature in a sealed jar until use. One part root powder was mixed with 10 parts water and allowed to sit for 5 min. The mixture was then poured through a coarse filter to remove root particles. The supernatant was put in an atomizer and misted on pear shoots before introducing the psylla to the feeding arena. Feeding was allowed for 6 days. On days 1, 3, and 6 of the trial, the number of insects on each shoot (vs on the arena wall) was determined. After 6 days of feeding, the psylla were removed from the arenas and frozen for later dissection and determination of ovarian development. Adult winterform psylla produce honeydew in solid, generally oval-shaped pellets, and the number of pellets was determined in each feeding arena. A preliminary experiment in which ninhydrin was used to stain honeydew (Paguia et al. 1980) verified that our counting methods were accurate (correlation between counts of honeydew before and after staining was 0.98 [N = 48]). We also compared the size of pellets among treatments (third collection date only). After the November, 1994 feeding trial, five feeding arenas from each treatment combination were randomly selected and the honeydew was brushed onto petri dishes. Between 5-20 pellets in each petri dish were randomly chosen, and maximum length and J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 11 width measured using a dissecting microscope equipped with an ocular micrometer. The feeding experiment was analyzed as a two-factor (conditioning x shoot treatment) randomized block design, with collection date included as a blocking factor. The response variable was the number of honeydew pellets per arena. Interactions involving collection date were not significant (p > 0.25); thus, sums of squares associated with these interactions were combined with residual sums of squares, and the new residual term was used as the error for all tests (Bancroft 1964). Numbers of insects in contact with the pear shoot on days 1, 3, and 6 were compared among treatments with a two factor (conditioning x shoot treatment) repeated measures ANOVA. Size (length; width) of honeydew pellets was compared among treatments with a two factor (conditioning x shoot treatment) multivariate analysis of variance (MANOVA). All insects were dissected after the feeding trials to determine ovarian development. Development was scored using stages described in Krysan and Higbee (1990), in which 1 is most immature and 7 is mature (>50% of ovarioles with mature eggs). Stage 4 is considered to be the first clear indication of postdiapause development (Krysan and Higbee 1990). Stage 5 is the category at which the first mature egg is present. Scores were averaged for the four insects in a feeding arena, and mean scores compared among treatments with ANOVA. Spearman's rank correlation was used to determine whether ovarian development and honeydew production were associated. Ovarian development varied among the three collection dates (see below). We therefore removed the effects of collection date from the ovarian scores with ANOVA before estimating correlation. A one-way ANOVA was calculated using mean ovarian score as the dependent variable and collection date (with 3 levels) as the independent variable. Residuals obtained from the ANOVA were then used in the rank correlation analyses. RESULTS Conditioning significantly affected ovarian development (Fig. 1). Averaged over the three collection dates, development was most advanced in fenoxycarb-treated insects (mean ovarian score = 5.2; N = 48), intermediate in long-day insects (mean = 4.4; N = 48), and least advanced in control (short-day) insects (mean = 3.2; N = 46). Comparisons among pairs of means were all significant (p < 0.001; by single df contrasts). Effects were not constant across collection dates (significant collection date x conditioning interaction [p < 0.001]). Although the dates in Fig. 1 refer to two different years, the medians suggest that fenoxycarb had more effect on younger insects (those collected in November) than those presumably more deeply in diapause (December insects). By the late December collection, long-day conditions and fenoxycarb produced almost identical median scores (Fig. 1). The effects of the cucurbit extract on honeydew production were the same in all three conditioning treatments (Fig. 2; nonsignificant shoot treatment x conditioning effect [p = 0.45]). This result indicates that diapausing and postdiapause psylla were affected similarly by the extract. The extract significantly reduced honeydew production in all of the insects. Averaged over conditioning treatments, mean [+SE] honeydew production was 8.9 [2.1] pellets (N = 71) on treated shoots and 14.9 [2.1] pellets (N = 71) on untreated shoots (p = 0 04) 12 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 olks3J——_| ELI He Control C1 Long-day REsaas ~Fenoxy 23 Nov. 14Dec. 28 Dec. 1994 1993 1993 e|-_[ ]}——| ee NN oe 3 IFRS - Mean Ovarian Score ON wo KR TH OD AN — Figure 1. Box plots of effects of conditioning and collection date on ovarian scores; shoot treatments had no effect on mean score (p = 0.42). Upper and lower boundaries of boxes 75" and 25" percentiles, respectively. Line in box shows median. Error bars 10” and 90" percentiles. Solid circles are outlying points. $0 O=—©- CONTROL @—®@ TREATED HONEYDEW PELLETS PER ARENA SHORT LONG FENOXY DAY DAY Figure 2. Mean (+SE) honeydew production as a function of shoot treatment and conditioning. Open circles, untreated; filled circles, treated with extract. Conditioning also significantly affected honeydew production (Fig. 2; p = 0.001). Averaged over shoot treatment, mean [+SE] honeydew production was 6.8 [2.6] pellets for the control (N = 46), 9.3 [2.6] pellets for long-day insects (N = 48), and 19.7 [2.6] pellets for fenoxycarb-treated insects (N = 48). Single df contrasts indicated that the J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 13 control differed significantly from the fenoxycarb treatment (p < 0.001) but was similar to the long-day treatment (p = 0.48). Pellet size also differed significantly (p < 0.001) among conditioning treatments (shoot treatment effects were nonsignificant). Single df contrasts indicated that pellets were significantly larger in long-day and fenoxycarb-treated insects than in control insects (p < 0.001 for both contrasts). Pellets were similar in size between long-day and fenoxycarb-treated insects (p = 0.19). Numbers of psylla in contact with the pear shoot on days 1, 3, and 6 were not affected by shoot treatment (p = 0.95) or conditioning (p = 0.80). This result suggests that the differences in honeydew production among treatments were not due to differences in the amount of time the psylla were in contact with the pear shoot. Rank correlation analysis showed that ovarian scores and honeydew production were positively associated (Table 1). That is, insects that produced larger amounts of honeydew tended also to have more advanced ovaries, even within a conditioning treatment. Table 1. Correlation (Spearman's rank) between ovarian scores and honeydew production. Effects of collection date removed from scores before estimating correlation. Control Long-day Fenoxycarb Untreated 0.46 0.22 0.52 shoots (p = 0.026) (p = 0.29) (p = 0.010) (N = 23) (N = 24) (N = 24) Treated 0.22 0.49 0.44 shoots (p = 0.31) (p = 0.016) (p = 0.033) (N = 23) (N = 24) (N = 24) Combined 0.29 0.35 0.54 (p = 0.047) (p = 0.016) (p < 0.001) (N = 46) (N = 48) (N = 48) DISCUSSION The winter form of pear psylla is an important target for management, because control of this morph often prevents problems later in the year (Westigard and Zwick 1972). Current difficulties in controlling this stage with broad-spectrum insecticides have forced growers to consider other methods, including techniques that reduce feeding and oviposition (e.g., by applying oil in spring [Zwick and Westigard 1978] or, potentially, by using unpalatable pear varieties [Stuart et a/. 1989, Bell and Stuart 1990, Puterka et al. 1993}). The specific plant cues that cause probing and continuous feeding in psylla are unknown but, as in other Homoptera (Walker 1987, Walker and Gordh 1989), may include cues received at the plant surface (Ullman and McLean 1988, Horton and Krysan 1990). Quantification of honeydew production is commonly used in studies of Homoptera to screen plant varieties (Padgham and Woodhead 1988) or otherwise determine host suitability (Blua and Toscano 1994). We used this method to show that an extract from buffalo gourd, a nonhost species, caused reductions in feeding. Extracts from buffalo 14 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 gourd have been shown to cause reduced feeding in other insect species (Weissling et al. 1991), perhaps because of the presence of cucurbitacins (Metcalf et al. 1982). Weissling (unpublished data) showed that the extract also caused about a 50% reduction in oviposition by pear psylla in choice tests. A number of physiological and behavioral characteristics are associated with diapause, including delayed ovarian development and reduced feeding (Tauber et a/. 1986). We tested two specific hypotheses related to diapause in pear psylla. First, we tested whether feeding rates were higher in postdiapause psylla than in diapausing insects. Second, we tested whether feeding by diapausing insects was affected less by a nonhost extract than feeding by postdiapause insects. Numbers and size of honeydew pellets were both larger in fenoxycarb-treated insects than in short-day, diapausing insects. Long-day and short-day insects produced similar numbers of pellets, but pellets were larger for the long-day insects. These results support our first hypothesis. Our second hypothesis was prompted by the observation that diapausing psylla are numerous outside of the pear orchard, whereas late postdiapause psylla or reproductive psylla are rarely encountered outside of the orchard. Thus, psylla evidently is a more generalized feeder in diapause than when out of diapause. Support for our second hypothesis would have been provided by a significant shoot treatment x conditioning effect in the analysis of variance. No such effect was noted; rather, the extract caused significantly reduced feeding in all insects, independent of diapause status. Finally, there was evidence that feeding rates and ovarian development were associated (Table 1). Compounds that strongly deter feeding might therefore be used to cause a delay in oviposition. Horton et a/. (1994) showed that postdiapause development of winterform psylla that overwintered on nonhost species was slower than that of insects that overwintered on pear, results that appear to be consistent with observations in this study. Growers regularly use a spring oil application to delay egglaying by winterform psylla. Our results show that compounds other than oil might also prove to be useful as feeding deterrents or for delaying oviposition. ACKNOWLEDGMENTS The comments of Carrol Calkins, Rick Redak, and Tom Unruh on an early draft are appreciated. We also thank Peter Belton and two anonymous reviewers for a number of helpful comments. The Washington Tree Fruit Research Commission and Winter Pear Control Committee provided financial support. REFERENCES Bancroft, T.A. 1964. Analysis and inference for incompletely specified model involving the use of preliminary test(s) of significance. Biometrics 20: 427-442. Bell, R.L. and L.C. Stuart. 1990. Resistance in eastern European Pyrus germplasm to pear psylla nymphal feeding. HortScience 25: 789-791. Blua, M.J. and N.C. Toscano. 1994. Bemisia argentifolii (Homoptera: Aleyrodidae) development and honeydew production as a function of cotton nitrogen status. Environ. Entomol. 23: 316-321. Hodgson, C.J. and T.M. Mustafa. 1984. The dispersal and flight activity of Psylla pyricola Foerster in southern England. Lutte integree contre les psylles du poiner. Bull. Org. Int. Lutte Biol. Sect. Reg. Ouest Palearct. 7: 97-124. Horton, D.R. and J.L. Krysan. 1990. Probing and oviposition-related activity of summerform pear psylla (Homoptera: Psyllidae) on host and nonhost substrates. Environ. Entomol. 19: 1463-1468. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 15 Horton, D.R., B.S. Higbee and J.L. Krysan. 1994. Postdiapause development and mating status of pear psylla (Homoptera: Psyllidae) affected by pear and nonhost species. Ann. Entomol. Soc. Amer. 87: 241-249. Kaloostian, G.H. 1970. Transitory hosts of the pear psylla. J. Econ. Entomol. 63: 1039-1041. Krysan, J.L. 1990. Fenoxycarb and diapause: a possible method of control for pear psylla (Homoptera: Psyllidae). J. Econ. Entomol. 83: 293-299. Krysan, J.L. and B.S. Higbee. 1990. Seasonality of mating and ovarian development in overwintering Cacopsylla pyricola (Homoptera: Psyllidae). Environ. Entomol. 19: 551-557. Metcalf, R.L., A.M. Rhodes, R.A. Metcalf, J. Ferguson, E.R. Metcalfand P.Y. Lu. 1982. Cucurbitacin contents and Diabroticite (Coleoptera: Chrysomelidae) feeding upon Cucurbita spp. Environ. Entomol. 11: 931-937. Padgham, D.E. and S. Woodhead. 1988. Variety-related feeding patterns in the brown planthopper, Nilaparvata lugens (Stal) (Hemiptera: Delphacidae), on its host, the nce plant. Bull. Entomol. Res. 78: 339-349. Paguia, P., M.D. Pathak and E.A. Heinrichs. 1980. Honeydew excretion measurement techniques __for determining differential feeding activity of biotypes of Nilaparvata lugens on rice varieties. J. Econ. Entomol. 73: 35-40. Puterka, G.J., R.L. Bell and S.K. Jones. 1993. Ovipositional preference of pear psylla (Homoptera: Psyllidae) for resistant and susceptible pear. J. Econ. Entomol. 86: 1296-1302. Stuart, L.C., B.A. Butt and R.L. Bell. 1989. Effect of host phenology on ovipositional preference of winter form pear psylla (Homoptera: Psyllidae). J. Entomol. Soc. Brit. Columbia 86: 34-38. Tauber, M.J., C.A. Tauber and S. Masaki. 1986. Seasonal adaptations of insects. Oxford University Press, New York. Ullman, D.E. and D.L. McLean. 1988. Feeding behavior of the winter-form pear psylla, Psylla pyricola (Homoptera: Psyllidae), on reproductive and transitory host plants. Environ. Entomol. 17: 675-678. Walker, G.P. 1987. Probing and oviposition behavior of the bayberry whitefly (Homoptera: Aleyrodidae) on young and mature lemon leaves. Ann. Entomol. Soc. Amer. 80: 524-529. Walker, G.P. and G. Gordh. 1989. The occurrence of apical labial sensilla in the Aleyrodidae and evidence for a contact chemosensory function. Entomol. Exp. Appl. 51: 215-224. Weissling, T.J., L.J. Meinke and K.A. Lytle. 1991. Effect of starch-based corn rootworm (Coleoptera: Chrysomelidae) baits on selected nontarget insect species: influence of semiochemical composition. J. Econ. Entomol. 84: 1235-1241. Westigard, P.H. and R.W. Zwick. 1972. The pear psylla in Oregon. Oregon Agnic. Expt. Station Tech. Bull. 122. Zwick, R.W. and P.H. Westigard. 1978. Prebloom petroleum oil applications for delaying pear psylla (Homoptera: Psyllidae) oviposition. Can. Entomol. 110: 225-236. Sz ep hee s ¥ ‘ ar ea a. ° ty i ” Oran | ee bie J. ENTOMOL. SOC. COLUMBIA, 92, DECEMBER, 1995 17 Monitoring and dynamics of a Douglas-fir beetle outbreak in Jasper National Park, Alberta LISA C. PAULSON PARK WARDEN, 623 PATRICIA STREET (BOX 10) JASPER, ALBERTA TOE 1EO ABSTRACT A Douglas-fir beetle outbreak in Jasper National Park was discovered at 10 sites in 1991, and has since expanded to 30 sites in 1992, and 55 sites in 1993. Individual sites surveyed in 1993 contained from 3 to more than 200 attacked trees covering areas of 10 m’ to 1 km? respectively. Sites containing pheromone population monitoring funnel traps contained significantly more attacked live trees than those sites without pheromone traps, suggesting that the traps attract larger beetle populations to the site. Diameter measurements indicated that in the initial years (~1990) of the infestation, larger diameter trees were attacked more commonly. In 1993, freshly attacked green trees were of a smaller diameter. INTRODUCTION Jasper National Park's montane forest is unique because it contains the most northerly stands of natural Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) in Alberta. Within Jasper Park's 10,920 km?, a computer analysis of the Jasper Biophysical Vegetation Map (Holland and Coen 1982) shows only 0.02% (167 km’) with Douglas-fir asa dominant tree and 0.01% (145 km’) with Douglas-fir as a subdominant tree. The stands infested by Douglas-fir beetle (Dendroctonus pseudotsugae Hopk.) are pure or mixed structures with individual trees as old as 575 years. The stand composition for sites with and without pheromone traps are similar, and both site types are near infested hosts. In Jasper Park, there have been minor Douglas-fir beetle (DFB) infestations consisting of 60 trees in 1980 and three trees in 1986. The onset of the current infestations was first observed near Annette and Patricia lakes in 1987 (Cerezke and Edmond 1989). In 1988, additional sites were found between Jasper townsite and the west gate (Edmond and Cerezke 1989). It was not until 1990/91 that the DFB infestations became well established in several stands of mature Douglas-fir in Jasper and were present in low numbers in Kootenay, and Yoho National Parks (Cerezke eft a/. 1991). At the time of this study (1993), the Jasper Park infestation was the only one known in Alberta. DFB infestations have occurred previously in southern Alberta and caused an estimated loss of 538,000 and 238,000 m? (19 and 8.5 million ft*) of timber in the Interior and Coastal regions of British Columbia between 1956 and 1970 (McMullen 1977). Since the discovery of 10 DFB sites in Jasper Park in 1991, the number has increased to 30 in 1992, and 55 sites in 1993, each with 3 to over 200 attacked trees (Figure 1). The current outbreak of DFB in Jasper appears to parallel that in British Columbia; where tree mortality from DFB covered 115 ha in 1989, 800 ha in 1990, 1,500 ha in 1991, and 3,425 ha in 1992 (Humphrey and Ferris 1992). Almost half the damage in 1993, 1,400 ha, was in the Mount Robson Forest District, bordering Jasper National Park to the west. 18 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Douglas-fir beetles are an important component of Douglas-fir montane forests, normally attacking weakened or dying Douglas-fir trees. Stand-age, lack of tree vigour, and disturbances (i.e. windstorms, root rot, drought, insect defoliation, and fire) are key factors that may increase DFB populations and allow them to attack standing Douglas-fir trees (Furniss ef ail. 1981). This may result in an aggregate pattern of attacked healthy trees leading to a "fine-scale gap dynamics that favour establishment and (or) the release of the next generation of its host, suggesting a co-evolutionary relationship", as Peterman (1978) suggested for mountain pine beetle in lodgepole pine forests. The reasons for the current infestation in Jasper are speculative. In 1989 before the height of the DFB outbreak, severe winter windstorms added to the dead Douglas-fir material available for DFB. In 1989, Parks Canada lit a prescribed fire in the sub-alpine forest region, east of Highway 16 and north of Jasper townsite, near some of the largest current DFB infestations. Some Douglas-fir trees may have been weakened or killed by spot fires associated with the main fire block allowing Douglas-fir beetles to multiply and move to nearby Douglas-fir stands that were not affected by the fire. Finally, the drought conditions of the early 1990's may have stressed Douglas-fir trees making them more susceptible to DFB attacks. Jasper National Park's main purpose is to promote public understanding, appreciation, and respect for Canada's natural and cultural heritage. Its mandate states that the Park exists for its intrinsic value as an important component of the larger regional ecosystem. Park managers recognize the DFB as an important agent disturbing the natural Montane ecosystem. In 1992, Parks Canada initiated detailed monitoring of DFB, consisting of aerial surveys and two sites baited with pheromone funnel traps for population monitoring. This was continued in 1993 and the number of pheromone-baited sites was expanded to six. The purpose of my 1993 study was three-fold: 1) to continue aerial monitoring of the number and size of infestation sites; 2) to determine if the DFB initially favours larger diameter trees; and 3) to determine whether the presence of pheromone- baited traps increased the numbers of green attacked trees in baited sites. METHODS Stands where Douglas-fir is the dominant or sub-dominant tree species were identified using Jasper Park's biophysical vegetation maps (Holland and Coen 1982). Aerial surveys were conducted to map DFB outbreaks in these stands, as indicated by more than 2 or 3 clumped red or recently dead trees. Subsequent ground surveys were made for as many of the sites identified by air during the summer of 1993 as time would allow. Twenty-nine of the 55 sites identified by aerial surveys were checked. Ground surveys consisted of counting the number of beetle attacked trees that were dead and had no-foliage (bare), red foliage, yellow foliage, or green foliage, taking the diameter at breast height (DBH) of each of these trees, and verifying the location of each site. Because the surveyed infestations were only a few years old, I assumed that dead, red, and yellow trees were attacked three to five, two, and one year(s) ago respectively. I assumed that green attacked trees were attacked during the first or second beetle flight of 1993. On one site where attacked green trees continued up-slope for some distance, trees were counted on a line randomly placed across the slope. A second site contained pheromone traps and trees within three 50 m* plots were sampled because this site had an obvious spotted infestation pattern over 500 m*. Since the sampling method for these two sites was inconsistent with that used for all other sites, the second attack site was excluded from calculations related to the effect of pheromone traps, but both sites were J. ENTOMOL. SOC. COLUMBIA, 92, DECEMBER, 1995 19 used to determine the mean diameters of each infestation category (no-foliage, red, yellow, and green) for sites with and without pheromone traps. Multiple funnel traps (Lindgren 1983) containing ethanol, frontalin (1, 5-dimethyl-6, 8-dioxabicyclo [3.2.1]Joctane), and MCOL (1-methycyclohex-2-enol) were used to monitor annual beetle population fluctuations. Lindgren (1992) found frontalin to be an effective aggregation pheromone for the DFB. Traps were placed in six sites (the two sites used in 1992 and four additional sites in 1993) under the direction of Dr. H. Cerezke of Forestry Canada (Figure 1). Scal ‘ cale 0 1 2 km PT JASPER @ Douglas fir beetle infestation Seana PT Pheromone trap hice Highway No. (23 ) i Figure 1. Douglas-fir beetle infestations in Jasper Park (inset). Sites with pheromone traps are marked. 20 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 The sites were chosen because they had active beetle populations and were accessible. Site size or possible tree stressing factors were not a factor in site selection. Each trap site contained three funnel traps, spaced 40 meters apart, in a triangle. Each trap was hung 2 meters above the ground on non-host trees. The traps were checked weekly to ensure they were intact and functional, and to collect captured beetles. Data Analysis The mean logarithms of tree diameter for each infestation category (no-foliage, red, and green) were compared using a two-sample, one-tailed t-test at the 99.5% confidence level. The yellow foliage category was not analyzed since very few trees had turned yellow, perhaps as a result of a cool and wet summer. The diameters were transformed to logarithms to give normal distributions. A total of 1,611 trees from all 29 infested sites was used in the diameter comparison. The logarithms of diameters were compared between sites with and without pheromones to determine if the pheromone had an effect on the diameter of any infestation category. All sites were used because there was no significant difference between the mean diameters of infestation categories in sites (excluding sampled sites) with and without pheromone traps. To assess the effect of the pheromone traps on the infestations, first, the numbers of green attacked trees in sites with and without pheromone traps were compared using a two-sample, one-tailed t-test at the 99.5% confidence level. Secondly, to determine if the extent of the current infestation is related to its initial size, a correlation analysis of the number of bare (no-foliage) trees to the current number of green attacked trees was performed. These analyses assume that since the infestation in the Park is fairly new, the bare trees were attacked 3-5 years ago and the green trees with fresh boring dust were attacked in 1993. RESULTS From a total of 1,611 trees, the geometric mean diameter (DBH) for attacked bare (no- foliage) and red trees was 43 cm and 48 cm respectively. These were significantly different from each other (Table 1). Both bare and red trees had a mean diameter significantly larger than attacked green trees, mean DBH = 39 cm (t = 3.59 and 10.44 respectively, p = 0.005). Table 1 Mean diameters (DBH) of four classes of attacked Douglas-fir trees in 29 sampled sites Parameter Greentrees Yellowtrees Red trees Trees with no foliage No. of trees 685 78 450 398 Mean (cm) 39 42 48 43 Log mean 1.596 1.623 1.684 1.631 Std. dev. 0.1 0.2 0.1 0.2 The five sites with multiple funnel traps (one trap site was excluded) had a significantly greater proportion of attacked green trees than sites without pheromone traps (Figure 2) (t = 3.32, DF = 20, p > 0.005). There was no linear relationship between the initial infestation size (number of attacked trees without foliage) and the current size (number of attacked green trees), since the x-coefficient (r = 0.26) was not significantly different from zero. Figure 2 shows that sites with pheromone traps were among those with the most attacked green trees. J. ENTOMOL. SOC. COLUMBIA, 92, DECEMBER, 1995 21 60 50 40 30 Mean % of all attacked trees 22 siles without pheromones 5 sites with pheromones Figure 2. Comparison of the mean percent attacked green,(G) yellow,(Y) red,(R) and trees without foliage (N-f), for sites with and without pheromones. Two sampled sites, one with pheromones and one site without, are excluded from the analysis. Of 1611 Douglas-fir trees surveyed, 547 were in sites with, and 1064 in sites without pheromones. DISCUSSION The mean DBH of the no-foliage and red trees in all surveyed sites was 4 to 8 cm larger than that of the attacked green trees. In Idaho, Furniss ef a/. (1981) found that attacks tended to be more dense and more successful on larger size diameter trees since they produce more resin than the smaller diameter trees. Initially a high resin production may increase tree resistance, but the resin may also contain kairomones or pheromone precursors that attract more beetles, increasing the probability of a successful attack. The beetle population in Jasper Park may now be large enough to overwhelm the smaller diameter trees. The mean diameter comparison, for each infestation category, used all infestation sites since there was no apparent difference between the mean logarithmic diameters of each category in sites with and without pheromones. This could be because the study design was not detailed enough to pick-up variances in attacked diameters with increased distance from the pheromone traps. Knopf and Pitman (1972) found that within a 10 m radius of the baits, 58% of 10 cm and larger diameter trees were attacked and larger diameters were progressively favoured as the distance increased from 4.3 -10.0 m. There was a significant positive correlation between pheromone baited sites and the number of green attacked trees. Surprisingly, a large initial infestation (number of attacked trees with no-foliage) did not correspond to a large number of attacked green trees. Therefore, the current number of green attacked trees may be related to the recent practice of pheromone baiting. Figure 2 shows that sites containing pheromone traps were among those with the highest number of green attacked trees. Baker and Trostle (1973) also found that frontalin and camphene pheromones attracted more beetles into an area when 58.5% of the trees within 33 feet of the baits were attacked and only 3.6% were attacked in the control sites. 22 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Although the pheromone sites had more green attacked trees, some of them may survive. In Montana, out of 739 attacked 188-year-old trees, 29% were unsuccessfully attacked (no reproductive galleries were established) and 22% of the trees survived the attack (Furniss et a/. 1981). To minimize stress on the attacked Douglas-fir trees in the Park, I did not remove the bark to investigate the galleries. It is likely that a similar proportion of our green attacked trees may survive. The DFB pheromone baits may have shifted and concentrated the attack centres to trees with funnei traps. The pheromone baits can result in spill-over onto neighbouring green host trees (Thier and Weatherby 1991), resulting in an increased concentration of natural pheromones, and thus significantly increasing the attractiveness of neighbouring trees. Stock ef al. (1994) found a similar concentrating effect with aggregating pheromones of western balsam bark beetle Dryocoetes confusus. Placing pheromone traps in Douglas-fir stands for population monitoring over several years may give misleading results. During the first few years of trapping it may appear that the beetle populations are increasing or have stabilized at a high level. Due to the continual pheromone emission from the traps combined with the natural tree and beetle pheromones many beetles may be attracted to the trapping site, causing an overestimate of population levels in the stand. Once most of the susceptible green trees are attacked in that locality, the populations may disperse, resulting in fewer beetles in the pheromone traps. This may give the false notion that the population has declined. Some researchers now suggest that the pheromone lures be placed at least 100 m from the nearest Douglas-fir tree. This may reduce the risk of establishing and intensifying infestations in surrounding stands. However, if the baits are placed in the same place year- after year, the results may still vary as the beetle infestation centres move through the forest over time. This would make it extremely difficult to determine population trends. Pheromone traps have great potential in managed forests for attempting to contain certain insect outbreaks and for determining if a particular insect is present or absent. However, the results obtained over successive years from monitoring DFB population trends with pheromone traps may be difficult to interpret. In National Parks designated as wilderness or preserves with natural ecological processes, monitoring beetle populations with pheromone traps may be inappropriate. Pheromone traps are likely to alter beetle populations and the forest stand structure by modifying the number of trees attacked and killed, the infestation centres, and the diameter of trees attacked. Jasper Park will continue to monitor the Douglas-fir beetle infestations aerially, but will no longer use pheromones. No plans have been made to control the infestations. Instead, park personnel conduct and encourage non-intrusive monitoring of the dynamics of the Douglas-fir beetle infestations and their effects upon its montane forest ecosystem. ACKNOWLEDGEMENTS I thank Dr. Kevin O'Hara, University of Montana, and Dr. Herb Cerezke, Canadian Forest Service, for their continual guidance and support throughout the project. I was assisted in the field by Richard Parsloe, Jordy Shepherd, Lanny Shepherd, Simon Curran, and Steve Pakulak. Lelani Arris, of Essential Elements, assisted with the statistical interpretation of the data. I thank Dr. Staffan Lindgren, University of Northern British Columbia; Dr. Les Safranyik, Canadian Forest Service; Dr. Hans Zuring, University of Montana and John Taylor, Assistant Chief Warden, Jasper Park, for their helpful comments. J. ENTOMOL. SOC. COLUMBIA, 92, DECEMBER, 1995 Zs REFERENCES Baker, B.H. and G.C. Trostle. 1973. Douglas-fir beetle attraction and tree-group response. J.Econ.Entomol. 66:1002-1005. Cerezke, H.F. and F.J. Emond. 1989. Forest insect and disease conditions in Alberta, Saskatchewan, Manitoba, and the Northwest Territories in 1987. For. Can., North. For. Cent. Edmonton, Alberta. Inf. Rep. NOR-X-300. Cerezke, H.F., F.J. Emond , and H.S. Gates. 1991. Forest insect and disease conditions in Alberta, Saskatchewan, Manitoba, and the Northwest Terntories in 1990 and predictions for 1991. For. Can., Northwest Reg., North. For. Cent., Edmonton, Alberta. Inf. Rep. NOR-X-318. _ Emond, F.J. and H.F. Cerezke. 1989. Forest insect and disease conditions in Alberta, Saskatchewan, Manitoba, and the Northwest Territories in 1988 and predictions for 1989. For. Can., North. For. Cent. Edmonton, Alberta. Inf. Rep. NOR-X-303. Furniss, M.M., R.L. Livingston, and Mark D. McGregor. 1981. Development of a stand susceptibility classification for Douglas-fir beetle in Hazard-Rating Systems in Forest Insect Pest Management: Symposium Proceedings. USDA Gen. Tech. Report. pp.115-128. Holland, W.D. and G.M Coen. 1982. Ecological (Biophysical) Land Classification of Banff and Jasper National Parks. Alberta Institute of Pedology, No. SS-82-44. Humphrey, N. and B. Ferris. 1992. Forest Insect and Disease Conditions Prince George Region, Forestry Canada, Pacific Forestry Centre Victoria, B.C. Sth Report-93-4. pp.16-17. Knopf, J.A.E. and G.B. Pitman. 1972. Aggregation for pheromone manipulation of the Douglas-fir beetle. J. Econ. Entomol. 65:723-726. Lindgren, B.S. 1983. A multiple funnel trap for scolytid beetles (Coleoptera). Can. Entomol. 115:289-294. Lindgren, B.S. 1992. Attraction of Douglas-fir beetle, spruce beetle and a bark beetle predator ( Coleoptera: Scolytidae and Cleridae) to enantiomers of frontalin. J. Entomol. Soc. Bnt. Columbia 89, December. McMullen, L.H. 1977. Pest Leaflet #14. Canadian Forestry Service, Pacific For. Research Centre. Peterman, R.M. 1978. The ecological role of the mountain pine beetle in lodgepole pine forests. In Theory and Practice of Mountain Pine Beetle Management in Lodgepole Pine Forests -A Symposium. 25-27 Apr. 1978, Washington State University, Pullman. Edited by A.A. Berryman, G.D. Ammam, R.F. Schmitz, and D.L. Kibee. Forest, Wildlife and Range Experiment Station, University of Idaho, Moscow. pp. 16-26 Stock, A.J., J.H. Borden, and T.L. Pratt. 1994. Containment and concentration of infestations of the western balsam bark beetle, Dryocoetes confusus (Coleoptera: Scolytidae), using the aggregation pheromone Exo-brevicomin. Can. J. For. Res. 24:483-492. Thier, R.W. and J.C. Weatherby. 1991. Mortality of Douglas-Fir after two semio-chemical baiting treatments for Douglas-fir beetle (Coleopetera: Scolytidae). J. Econ. Entomol. 84:3:962-964. » Ps . 2. a ta es a ‘ : i git . An. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Zo Larch sawfly, Pristiphora erichsoni (Hymenoptera: Tenthredinidae) and its parasitoids from Alaska JAMES A. RICHMOND’, RICHARD A. WERNER’ and ARNOLD T. DROOZ’ ‘USDA FOREST SERVICE, RESEARCH TRIANGLE PARK, NORTH CAROLINA 27709 "USDA FOREST SERVICE, FAIRBANKS, ALASKA 99775 *USDA FOREST SERVICE (RETIRED), CARY, NORTH CAROLINA 27511 ABSTRACT The larch sawfly and four parasitoids were reared in the laboratory from cocoons collected in Alaska for two consecutive years. Emergence of adult sawflies exceeded thirty percent each year. The number of parasitoids emerging was four times greater from the 1993 collection than from the subsequent year. Twelve Tritmeptis klugii (Ratzeburg) emerged from one cocoon of the 1993 collection. The emergence of Delomerista laevis (Gravehorst) from the same collection established a new host record. Mesoleius tenthredinis Morley was the most common parasitoid that emerged from cocoons collected in 1993, and the only one that emerged from cocoons collected in 1994. Key words: Rearing, sawfly, Tachinidae, Ichneumonidae, Pteromalidae INTRODUCTION The larch sawfly, Pristiphora erichsonii (Hartig), is a Holartic destructive insect on Larix spp. (Drooz 1960). Insects feeding on the leaves of hosts stunt tree growth and may kill the tree. Schmiege (1966) first reported the larch sawfly in Alaska. He collected specimens near Fairbanks in 1965 and found evidence that the sawfly had been in the area since at least 1960. He did not note the presence of its parasites. Our rearing of adult sawflies and parasitiods from cocoons provides the first information on emergence in the laboratory of both specimens from Alaska. MATERIALS AND METHODS Cocoons of the larch sawfly were collected from leaf litter 32 km east of Fairbanks, AK in September 1993 and 1994. Approximately 400 cocoons were shipped to Cary, NC in September each year in a ventilated box that contained damp sphagnum. Cocoons collected in 1993 were stored at 4°C until 1 April 1994 when 170 fungus-free cocoons were placed individually into plastic boxes that were incubated at 18+2°C. Cocoons collected in 1994 were stored at 4°C until 15 March 1995 when adult sawflies began to emerge. On 17 March 1995, 200 fungus-free cocoons were incubated. Moisture in the plastic boxes was maintained by wetting blotter paper beneath the boxes. This technique provides a suitable microenvironment, and precludes the escape of Tritneptis klugii (Ratzeburg) (Hymenoptera: Pteromalidae) and additional parasitization of cocoons during Tearing (Drooz and Thompson 1986). It also aids in culling fungus-infected cocoons. 26 J. ENTOMOL. SOC. BRIT. COLUMBIA, 92 DECEMBER, 1995 Data on the emergence of sawflies and parasitoids were recorded. Parasitiods were identified and voucher specimens deposited at the USDA Systematic Entomology Laboratory, Beltsville, MD. Q c 5 z fo) o £ = =) < z re") x Date 25 100 “J No. sawflies No. parasitoids iS ; 20 | cS 80 Cum. % sawilies + cum. % parasitoids “i _ 15 60 = 3 =. E = Zz S 10 40 x 20 aq [es Bs BS ea be 410 4/7 4/10 4/11 4/12 4/134/14 4/17 6/18 4/20 4/21 4/244/28 B11 G/2 §& Date 3/733/1853/163/29 4/3 4/4 4/5 Figure 1. Number and cumulative percent of larch sawflies, Pristiphora erichsonii and parasitoids reared in 1994 and 1995 in the laboratory from cocoons collected in September 1993 and 1994 in Alaska. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 27 RESULTS AND DISCUSSION During laboratory rearing 74 adult sawflies and 30 adult parasitoids emerged from the 1993 collection, and 122 sawflies and 7 parasitiods emerged from the 1994 collection (Fig 1). For the 1994 rearing, larch sawflies began emerging 14 days after incubation began and continued for about 1 month. Most sawflies emerged between the second and third week, at which time parasitoids also started to emerge. The start of parasitoid emergence is similar to that seen when rearing Olesicampe benefactor Hinz (Hymenoptera: Ichneumonidae), a common parasite of the larch sawfly (Drooz and Thompson 1986). Of the 30 parasitoids that emerged from the 1994 rearing, 2 were Bessa harveyi (Townsend) (Diptera: Tachinidae); 14 were Mesoleius ftenthredinis Morley (Hymenoptera: Ichneumonidae); 2 were Delomerista laevis (Gravenhorst) (Hymenoptera: Ichneumonidae); and 12 were T. A/ugii_ that emerged from one cocoon on 6 May. Almost all B. harveyi, T. klugii, and M. tenthredinis emerged after the peak of host emergence. D. laevis, a new host record, emerged on 9 May, after most of the hosts. For the 1995 rearing, 10 adult sawflies emerged at 4°C on March 15 and 16 before cocoons were incubated (Fig. 1). After 200 cocoons were incubated on March 17, an additional 112 sawflies and 7 parasitoids also emerged. All of the parasitioids were M. tenthredinis. Peak emergence of sawflies occurred between April 3 and 10, earlier than peak emergence for the 1994 rearing. The larch sawfly in Alaska is host to parasites native to Alaska and to one previously found only in other areas of North America. B. harveyi, D. laevis, and T. klugii are native parasites that attack across families of sawflies. In contrast, M/. tenthredinis, a host specific parasitoid, was introduced into Canada from England in 1910 (Hewitt 1912). Subsequent releases were made in eastern and central Canada (Criddle 1928), and it was released in southeastern British Columbia in 1934 (Hopping ef a/. 1943). It was never released in Alaska, and we suggest it arrived there with the northwestern migration of its only known host, the larch sawfly. ACKNOWLEDGEMENTS Specimens were identified by N. E. Woodley (Tachinidae), R. W. Carlson (Ichneumonidae), and D. R. Smith (Tenthredinidae) of the Systematic Entomology Laboratory, U. S. D. A., Beltsville, MD. We thank David R. Smith, Lynne C. Thompson and Michael R. Wagner for comments and suggestions. We appreciate the assistance of Jamie S. Godfrey and Christopher A. Graves for preparing the graphs. REFERENCES Criddle, N. 1928. The introduction and establishment of larch sawfly parasites, Mesoleius tenthredinis Morley, into southern Manitoba. Can. Entomol. 60: 51-53. Drooz, A. T. 1960. The larch sawfly: Its biology and Control. USDA For. Serv., Tech. Bull. 1212: 1-51. Drooz, A. T. and L. C. Thompson. 1986. Collecting, rearing, shipping, and monitoring Olesicampe benefactor (Hymenoptera: Ichneumonidae), parasites of the larch sawfly, Pristiphora erichsonii (Hymenoptera: Tenthredinidae). Great Lakes Ent. 19: 181-184. Hewitt, C. G. 1912. The large larch sawfly (Nematus erichsonii). Can. Dept. Agric. Entomol. Bull. 5: 142. Hopping, G.R., H. B. Leach and C. V. G. Morgan. 1943. The larch sawfly, Pristiphora erichsonii (Hartig) in British Columbia, with special reference to the cocoon parasites, Mesoleius tenthredinis Morley and Trimeptis klugii (Ratzeburg). Sci. Agni. 24: 53-63. Schmiege, D. C. 1966. A note on the occurrence of the larch sawfly in Alaska. Can. Entomol. 98: 671-672. = ———— > J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 Zo The impact of codling moth (Lepidoptera: Tortricidae) mating disruption on apple pest management in Yakima Valley, Washington ALAN KNIGHT USDA, ARS 3706 W. NOB HILL BLVD, YAKIMA, WA 98902 ABSTRACT From 1991 to 1993, pheromone-based mating disruption for control of codling moth, Cydia pomonella (L.)was evaluated in seven apple orchards. Each pheromone-treated orchard was paired with a similar orchard without pheromone. Populations of codling moth, secondary pests, and selected natural controls were monitored. The cost of using pheromone dropped nearly $100 per ha from 1991-1993 because of reductions in the price of dispensers and improved application. Growers saved $87-147 in insecticides per ha in pheromone-treated orchards, because of an 83% reduction in sprays for codling moth, but savings from reduced labor and machinery costs in treated orchards were minimal. Damage from codling moth was high in one treated orchard in 1991 (7.4%), and increased to 20.8% in 1992. The population density of codling moth was low in the other orchards (fruit injury < 0.4%) in all three years. Insecticide applications after petal-fall for secondary pests were reduced by 18% in treated orchards. Populations of secondary pests were similar between orchard pairs. Among natural controls only parasitism of leafminers differed significantly between treated and untreated orchards. In 1991, leafrollers caused > 3% fruit injury in three of seven treated orchards, but were not a problem thereafter. Substituting mating disruption for insecticides to manage codling moth in apple orchards may therefore be successful, but for the first three years, may not substantially improve biological control of secondary pests. Key words: Cydia pomonella, apple, mating disruption INTRODUCTION Apples are identified by the public in the United States as a wholesome food (Washington State Apple Commission 1993), yet they are one of the crops most heavily sprayed with pesticides (Pimental ef al. 1992). Increased public awareness and changes in social attitudes towards exposure to pesticides (Ottef a/. 1991) are forcing a reconsideration of existing pest management programs in tree fruits (Prokopy & Croft 1994). In the western U.S., codling moth, Cydia pomonella (L.) is the key pest of apples. Conventionally-managed orchards rely on a series of ‘cover sprays' during the season (Washington State University Cooperative Extension Service 1992). Organophosphate insecticides have been used almost exclusively for codling moth during the last 35 years, but resistance has recently been documented (Varela ef a/. 1993, Knight et a/. 1994a). Much of the effort to transform apple pest management in the western United States from broadspectrum pesticides to more biointensive methods has focused on using sex pheromones to disrupt mating of codling moth. Since the registration of a multicomponent polvethylene tube pheromone dispenser in 1991, successful field trials have been reported by Barnes er a/. (1992) and Pfeiffer et al. (1993). Researchers continue to evaluate mating disruption of codling moth and to optimize its efficacy and 30 J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 cost (Knight 1992). Yet the effect of adopting this technology on the complex of secondary pests and natural enemies in apple orchards is unclear. A three year study was conducted from 1991 to 1993 to evaluate the use of polyethylene tube dispensers in commercial apple orchards in the Yakima Valley. The objectives of this study were to evaluate the effect of mating disruption on: 1) the control of codling moth; 2) growers' spray schedules and cost of pest management; and 3) the population densities of some other pests and their natural enemies compared with similar orchards not treated with pheromone. MATERIALS AND METHODS Study Sites. Seven apple growers near Yakima treated a portion of their orchards in 1991 with 1,000 translucent polyethylene tube dispensers (Isomate-C®, Pacific Biocontrol, Davis, CA) per ha for codling moth. The dispensers were loaded with an average of 171 mg active ingredient of (E,E)-8,10-dodecadien-l-ol, 1-dodecanol, and 1-tetradecanol (63:31:6 blend); plus 13% inert ingredients (UV inhibitors and antioxidants). Each year, a single application of dispensers was applied in orchards before the moths emerged (third week of April to early May). Each grower's pheromone-treated orchard was paired with another without pheromone (designated as untreated). Paired orchards were matched for similar area, cultivar, tree size, and planting density and represented typical horticultural practices, including the use of insecticides, for this region (Table 1). Borders of paired orchards were usually separated by 100 to 200 m. Pest management advice was provided by farm managers and fieldmen from a local chemical supply company. Table 1 Apple orchards treated with pheromone dispensers for codling moth from 1991 to 1993. Each was paired with a similar untreated orchard Area treated (ha) Trees Mean tree Orchard 1991-1993* Cultivars /ha height (m) Yi 7.3-2.0 Rome & Granny Smith 598 3.5 Y2 7.0-7.0 Red Delicious & Golden Delicious 633 4.1 Y3 2.5-2:5 " " , " 527 3.6 Y4 6.5-6.5 " : ‘i ‘ 269 4.4 Y5 4.0-2.0 " " 4 664 3.8 Yy6? 8.0 ‘i s a 332 2.9 YY? 13 ‘ 5 : : 427 3.9 * Area treated with pheromone in 1991 and 1993. » Orchard Y6 was in the study from 1991-1992. © Orchard Y7 was in the study only in 1991. Evaluation of Costs. Costs associated with the pheromone dispensers were assessed by interviewing growers. Besides the growers in this study, 10 others using mating disruption were interviewed. The costs included the dispensers and labor ($6 per hr). Costs of insecticides were obtained from a local chemical supply company. Sprays applied only to orchard borders were counted as 0.2 and alternate-row middle sprays (every other row was sprayed) were treated as 0.5 of a full application. Sampling Pests and Natural Enemies. Population densities of various pest and beneficial insects were monitored in each orchard. These included: adult codling moth; a J.LENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 31 complex of green aphids, viz. Aphis pomi DeGeer, Rhopalosiphum fitchii (Sanderson), and Aphis spiraecola Patch; white apple leafhopper, Typhlocyba pomaria McAtee and its mymarid parasitoid, the Anagrus wasp; western tentiform leafminer, Phyllonorycter mespilella (Hiibner), and associated parasitoids; and larval populations of the leafroller moth, Pandemis pyrusana Kearfott. Sampling dates were chosen to coincide with periods of peak population densities of each pest. Fruit injured by codling moth and P. pyrusana was sampled at mid-season and just before harvest. Sampling protocols varied between years. All orchards were divided into four sections in 1991 and five sections (four edges and the middle of the orchard) in 1992-93. Edges were designated as the outer 20 m of the orchard. Trees, shoots, and leaves were sampled randomly along transects within each section. Green Aphids. Green aphids were sampled by counting the number of aphids on the most infested leaf per shoot (Hull & Grimm 1983). In 1991 they were counted on five shoots from 10 trees within each section from 14-22 August. During the next two years, they were sampled by counting the number of aphids on the most infested leaf per shoot from five shoots on 12 trees per section. Sample dates were 28-29 July, 1992 and 1-3 July, 1993, respectively. Five density classes were established: 1 = 0 aphids; 2 = 1-25; 3 = 26-100; 4 = 101-250; and § = > 250 aphids. The total number of generalist predators per shoot was also recorded. Leafhoppers. Adult white apple leafhopper and Anagrus sp. adults were sampled with sticky yellow cards (22.7 x 27.7 cm) (Trece Inc., Salinas, CA). The traps were placed at 2.0 m height in the tree canopy and were retrieved after 6-10 d. Five traps were placed in each section from 1-8 July, 1991. Five traps were again placed in each orchard during both adult flights 3-5 June and 4 September, 1992 and 17 June and 25-27 August, 1993. Results were recorded as the mean number of adult leafhoppers and parasites caught per day per trap. Leafminers. The density of immature leafminers was sampled in each orchard in 1991 on 15-19 July and 14-21 August by counting the number of mines on the third leaf down the shoot from the leaf visually selected. In each section, five leaves were sampled per tree from 10 trees. Levels of parasitism were assessed for each generation by dissecting 20 mines per section. Parasitism of first generation mines was assessed on 11- 12 June. In 1992, leafminers were sampled on 2-7 July and 23-29 September, by counting the number of recent mines per leaf on 10 leaves per tree on 20 trees. Levels of parasitism were assessed on 21-29 May, 8-9 July and 3 September by dissecting 100 mines per orchard. The number of first generation mines in 1993 was too low to assess percent parasitism. The protocol from 1992 was used to assess leafminer density and parasitism on 3-4 August and 25-26 August, 1993. In all three years, host feeding was included as a part of total parasitism (Barrett & Brunner 1990). Leafrollers. Larval populations densities were estimated by counting the number of rolled leaves per 1 minute of searching 20 trees per section from 12-14 June and 28-30 July, 1991. Sampling during 1992 and 1993 consisted of examining 40 terminal shoot tips (20 from the top and 20 from the bottom of the canopy) from 20 trees on 12-15 May and 9-14 July, 1992 and 20 May, 1993, respectively. Codling Moth. Two pheromone-baited traps (Scentry Inc., Buckeye, AZ) were placed in each section (separated by > 50 m) to monitor adult codling moth in 1991. One was baited with a red rubber septum loaded with | mg and the other with a septum loaded with 10 mg codlemone (Trece Inc., Salinas, CA). The septa were replaced every 4 weeks and type of septum was alternated between traps in each section. Traps at a density of one per 1.0-2.0 ha were placed in each orchard during 1992 and 1993. All traps in 32 J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 pheromone-treated orchards were baited with septa loaded with 10 mg of codlemone; traps in untreated orchards had 1 mg septa. Septa were replaced every 3 weeks. Trap liners were replaced as needed. Fruit Injury. Percent fruit injured by codling moth in 1991 was assessed on 2-3 July and for both P. pyrusana and codling moth prior to harvest (3-10 d) of each major cultivar (‘Golden Delicious' from 10-20 September and ‘Red Delicious', 'Rome' and ‘Granny Smith' from 2-9 October). Fruit injury was sampled in mid-season and at harvest along ten transects (examining 20 fruits from five consecutive trees) per section ( or 4,000 fruits per orchard). ? Mid-season fruit injury in 1992 was assessed on 19-30 June and injury prior to harvest from 3-17 September. Mid-season injury was sampled by visually inspecting from the ground 30 fruits high and 30 fruits low in the canopy of 100 trees (estimated to be equivalent to 6,000 half-fruits). Injury at harvest was measured by manually examining 15 fruits per height from 10 trees per section (1,500 fruits per orchard). Injury was sampled in 1993 mid-season from 18-23 June and prior to harvest on 11 September for 'Golden Delicious' and 23 September for late cultivars. On all three sampling dates, 15 fruits were manually examined at both heights from 10 trees per section (1,500 fruits per orchard). Fruit injury was weighted by the percentage of each cultivar in the orchard. Statistical Analysis. Aphid density classes in pheromone-treated and untreated orchards were compared on each date with Wilcoxon Signed Rank test (Hintze 1987). Means from all other counts were compared between treatments on each date using a paired t-test. RESULTS Cost of Using Pheromone. Costs varied among the seventeen growers interviewed depending on the way the dispenser was attached to the tree. The lowest cost (mean + SE) was for dispensers applied by hand from the ground (n=5, $27 + 7 / ha). However, in 1991 most growers (n=9) used ladders to apply dispensers in the upper third of the canopy. This method was the most expensive ($69 + 10 / ha) and was disliked by many growers because of the risk to workers. Workers of other growers applied dispensers from trailers pulled through the orchard by a tractor (n=3, $35 +5 / ha). With each method, costs were highest in orchards where growers trained their workers carefully and monitored their work. Beginning in 1992, many growers tied the dispensers onto plastic clips (Series W, No. 6, Kwik Lock Corp., Yakima, WA) and used a telescoping pole to attach dispensers at the recommended height in the canopy. The average cost of this method ($38 + 4 / ha) was similar to the use of trailers, but allowed growers greater flexibility in placing dispensers. The cost of the dispensers declined during this study from $326 / ha in 1991 to $272 / ha in 1993. Insecticide Usage. The number of sprays applied for codling moth in orchards treated with pheromone during this three-year study was 83% lower than in the untreated orchards (Table 2). The use of insecticides for codling moth in the pheromone-treated orchards was highest in 1992 as more growers either sprayed borders or supplemented their use of pheromone. In 1993, three growers applied a single insecticide spray to the border of their pheromone-treated orchards. J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 33 Table 2 Spray records and cost of insecticides in paired orchards treated with and without codling moth sex pheromone, 1991-1993, YakimaValley,WA Mean number of sprays applied per orchard 1991 1992 1993 Pest Pheromone None Pheromone None Pheromone None Codling moth 0.5 3.0 0.9 2.8 0.1 3.8 Leafrollers* 0.9(0.4) 1.1(0) 0.4(0.3) 0.8(0) 0.6(1.0) 0.6 (0.7) Leafminers 0.0 0.1 1.0 1.3 0.0 0.0 Aphids and 1:5 2.4 22 25 2.6 2.6 leafhoppers Mites 0.1 0.1 0.2 0.3 0.2 02 General 1.0 1.0 1.0 1.0 1.0 1.0 Mean cost ($)” 194.64 282.30 243.54 345.06 202.79 349.75 Materials used (/ ha) included: Guthion SOW (1.7-2.2 kg) and Imidan SOW (5.6-6.6 kg) for codling moth; Lorsban 5OW (3.4 kg) and Penncap-M 2F (7.0-9.3 liter)for leafrollers; Vydate 2L (0.6-2.3 liter) for leafminer; Phosphamidon 8E (0.6-0.9 liter), Sevin XLR (1.2- 1.8 liter) Thiodan 5O0WP (2.2-4.4 kg), Meta-Systox R 2E (3.5 liter), Phosdrin 4E (0.6 liter), Pyrellin (2.3 liter), Lannate 1.8L (0.6 liter), and Methoxychlor 50W (4.7 liter) for aphids and leafhoppers; Omite 30W (6.7-8.4 kg) for mites; and Lorsban 4E (4.7 liter) for general pests. Sprays applied to borders counted as 0.2; sprays applied to alternate row middles counted as 0.5. “Mean number of sprays of Dipel 2X (1.1 kg) / ha for leafrollers in parentheses. ° Mean cost is the total retail cost of all insecticides used during the season. Insecticides were applied for other pests in orchards both with and without pheromone (Table 2). Nearly all orchards in 1991 were sprayed during the summer for leafrollers. During the second year, growers switched from chlorpyrifos to encapsulated methyl- parathion to control leafrollers and fewer orchards were treated (Table 2). Following widespread bee poisoning from summer use of insecticides for leafrollers in 1992 (M. Willett, personal communication) the use of products containing Bacillus thuringiensis Berliner increased in 1993. All orchards were treated with 1 or 2 applications of insecticide for leafminer in 1992. Insecticides were widely used to control green aphids and leafhoppers during all three years of this study. Only 2 or 3 orchards were sprayed for mites each year (Table 2). The mean cost of insecticide materials per ha was higher in the untreated than in the pheromone-treated orchards each year, i.e. $87 more in 1991, $101 in 1992, and $147 in 1993 (Table 2). However, there were minimal savings from reduced operating costs in pheromone-treated versus untreated orchards because of the application of materials other than insecticides during the season (growers commonly mixed several insecticides, mineral supplements, herbicides, or fungicides together). No change was observed in the rates of chemicals used between orchard-pairs. Aphids. The population density of green aphids varied from year to year and no Significant difference was found between orchards with and without pheromone on the selected dates (Table 3). Few generalist predators were found in samples during 1991 and 1992 (< 1.0% of shoots had > 1 predator), and no difference in their population density was found between orchard pairs (Table 4). However, in 1993, 4.3% of the shoots 34 J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 in the pheromone-treated orchards had > 1 predator compared with 0.7% in the untreated orchards (p = 0.10). The most abundant predators were immature chrysopids, immature and adult coccinelids, immature syrphids, and adult hemipterans. Table 3 Mean (+ SE) population densities of some secondary pests in pheromone-treated and untreated apple orchards 1991 1992 1993 Pest sample Generation Pheromone None Pheromone None Pheromone None Mean density class: - 1.22(0.07) 1.23(0.06) 2.45(0.38) 2.50(0.28) 1.93(0.34) 1.76(0.29) green aphids / most infested shoot" No. leafhopper adults 1° 38.7(11.8) 31.8(7.0) 47.6(7.9) 88.0(30.1) 46.7(18.3) 64.5(40.9) per sticky trap Fi - - 86.8(33.4) 121.8(42.5) 14.2(17.7) 6.5(8.7) No. leafminer larvae 2% 0.19(0.06) 0.19(0.05) 5.44(1.64) 4.74(1.33) 0.22(0.10) 0.21(0.08) per leaf 3° 0.48(0.19) 0.33(0.11) 3.23(1.38) 2.50(0.80) 0.57(0.30) 0.96(0.49) No. leafroller larvae 1° 0.02(0.00) 0.06(0.4) 0.00 0.00 0.00 0.00 per shoot sample ia 0.11(0.04) 0.07(0.02) 0.00 0.00 0.00 0.00 % leafroller injury - 3.00(1.63) 0.8(0.35) 0.14(0.06) 0.09(0.05) 0.08(0.08) 0.04(0.04) Differences in aphid density ranks (p > 0.05, Wilcoxon Signed Ranks test) and other samples (p > 0.05, paired t-tests) not significant in any year between orchard types. * Aphid density classes: 0 aphids = 1; 1-25 = 2; 26-100 = 3; 100-250 = 4; and > 250 aphids = 5. Table 4. Mean (+ SE) population densities of some natural enemies in pheromone-treated and. untreated apple orchards 1991 1992 1993 Naturalenemy — Generation Pheromone None Pheromone None Pheromone None sample % shoots with - 0.71(0.62) 0.85(0.42) 1.73(0.61) 2.21(0.70) 4.34(1.83) 0.67(0.40) aphid predators No. adult Anagrus 1" 0.07(0.01) 0.10(0.07) 0.65(0.49) 0.34(0.28) 0.46(0.19) 0.44(0.24) / sticky trap Phe - 4 0.000.00 1.26(1.04) —0.26(0.21) % parasitism of 1% 30.9(3.9)a__-17.6(3.9)b_ — 6.2(2.9) 2.8(0.8) - - leafminer larvae 2 27.1(10.3) 21.2(9.0) —5.8(3.2) 0.7(0.5) 19.5(6.8) 11.2(3.7) 3" 42.9(9.3) 33.8(10.1) = 15.0(8.4) 13.8(5.8) 27.5(8.8)a_ —:12.2(5.5)b Means within year for each generation followed by different letters are significantly different, p < 0.05, paired t-test. Leafhoppers. Population densities of white apple leafhoppers were not significantly different between pheromone-treated and untreated orchards (Table 3). However, there was weak evidence (p = 0.09) of a reduced population density of second generation adults in 1992 in the pheromone-treated orchards. In general, there were fewer leafhoppers in pheromone-treated than untreated orchards during 1992 and 1993 (Table 3). Few Anagrus sp. were caught on sticky traps and numbers varied among orchards (Table 4). On two dates (first generation in 1992 and second generation in 1993) the density of this parasitoid was 1.8-4.1 times higher in the pheromone-treated than in untreated orchards, but these differences were not significant (Table 4). The ratio of adult parasites to leafhopper adults on traps on these two dates was also higher (4.2-6.7 times) in the treated than in the untreated orchards, but these differences were not significant (0.20 < p< 0.30). During the second generation in 1992, no adult parasites were found on sticky traps (Table 4). J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 35 Leafminers. The mean number of mines per leaf was low in all orchards in 1991 and their density only exceeded 1 mine per leaf in two pheromone-treated orchards during the third generation (Table 4). In contrast, populations were high (> 3 mines per leaf during second generation) in all but one pair of orchards 1992, and orchards were sprayed at least once with insecticide (Table 2). Leafminer populations were low in all orchards during 1993. Levels of parasitism of leafminers were higher in treated than untreated orchards, but the difference was only significant on two dates, first generation in 1991 and the third generation in 1993 (Table 4). Levels of parasitism were low in all orchards during 1992. Table 5 Catches of codling moths and fruit injury at harvest in-pheromone-treated and untreated orchards Mean moths / % fruit trap / season injury Orchard Treatment® 1991 1997 1993 199] 1992 1993 YI pheromone 1.0 4.0 0.0 0.00 0.16 0.00 none 16.0 6.5 0.0 0.25 0.08 0.10 Y2 pheromone 0.0 0.0 0.0 0.10 0.00 0.00 none 0.0 1.0 0.0 0.15 0.00 0.00 Y3 pheromone 3.0 3:3 0.0 0.25 0.17 0.05 none 20.3 76.0 17.5 0.20 0.00 0.00 Y4 pheromone 1.0 0.5 0.0 0.0 0.00 0.00 none 1.0 2:0 0.0 0.0 0.00 0.00 1 @) pheromone 0.3 1.0 1.0 0.40 0.00 0.33 none 1.8 6.0 ape) 0.15 0.00 0.00 Y6 pheromone 0.9 68.5 - 7.43 20.82 - none 14.5 150.0 - 0.42 0.17 - Y7 pheromone 0.3 - - 0.00 - - none 5.0 - - 0.00 - - * Traps in pheromone-treated and untreated orchards were baited with 10 mg and 1 mg lures, respectively. Leafrollers. Leafroller larvae were found overwintering in nearly all orchards in 1991 after the application of the delayed-dormant insecticide (Table 3). Fruit injury at harvest was greater than 3% in three orchards. No larvae were found in shoot terminal samples in 1992 and 1993, and fruit injury at harvest was low and restricted to two orchards during these two years (Table 3). Codling Moth. Traps baited with 10 mg codlemone in 1991 caught 2.1 times more moths than those baited with 1 mg in treated orchards. In contrast, traps baited with 1 mg in the untreated orchards caught 1.4 times more moths than traps baited with the 10 mg lure. Cumulative trap counts were low in all orchards in 1991, but increased in the untreated Y3 and both Y6 orchards in the second year (Table 5). Catches were low in all orchards in 1993. Levels of codling moth injury to fruit after the first generation in 1991 were low (<0.1%) in all orchards except in the pheromone-treated Y6 orchard. At harvest, injury in Y6 increased to 7.4% (Table 5). Cumulative moth catches per trap did not reflect this high level of injury (Table 5). Levels of injury were <0.4% at harvest in all other 36 J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 pheromone-treated and untreated orchards. Injury increased nearly three-fold in the pheromone-treated Y6 orchard in 1992. Damage in this orchard, as in 1991,. was primarily restricted to one edge of the orchard reaching about 65%. In 1992 and 1993, injury was low in all other orchards, <0.35% at harvest (Table 5). DISCUSSION Use of pheromones to disrupt mating of codling moth was effective in six of the seven apple orchards monitored from 1991 to 1993. In these orchards, the densities of codling moth remained low and use of insecticides for this pest was significantly reduced. The poor control of codling moth in orchard Y6 can be explained. This orchard had a previous history of codling moth injury and the density of the overwintering population in 1991 was unknown. In 1991, the pheromone was applied at a half rate (500 dispensers per ha) along the northeastern edge of the orchard by mistake. A number of physical characteristics found in this area of the orchard also reduced the effectiveness of mating disruption: a large number of missing trees (no pheromone was applied in areas with missing trees), an uneven canopy with tree heights ranging from 2.5 - 5.0 m, and a 6% slope. The adoption of mating disruption of codling moth by growers is currently limited by its high material cost relative to the use of insecticides (Williamson ef al. 1994). Further adoption will be enhanced by factors that can lower the cost of application, the cost of the dispensers, and/or the cost of supplementary insecticides applied for codling moth and other secondary pests. Dispenser application costs are likely to be high for any tie-on technique, and the need for applying dispensers in the upper canopy (Weissling & Knight, in press) will add to this cost. However, use of the telescoping pole and plastic clip has lowered the cost of application and improved placement. Nevertheless, alternative methods for using pheromones in tree fruits should be investigated. Broadcast application of dispensers has been tested previously for codling moth (Moffitt & Westigard 1984), and is used commercially for pink bollworm, Pectinophora gossypiella (Saunders) where labor costs are high (Brooks et a/. 1979). Expectations of growers (Alway 1991) and researchers (Barnes et al. 1992) that the adoption of mating disruption for codling moth will reduce insecticide use for other pests and enhance the role of biological control in tree fruits, were not met in this study. Less use of insecticides for secondary pests would add to the benefits of adopting mating disruption. For example, elimination of a single spray in a 'Delicious' orchard would save on average $71 per ha (Hinman ef al. 1992). Results from this study, however, showed that growers in the Yakima Valley continued to spray for secondary pests in pheromone-treated orchards, especially for aphids and leafrollers. Moreover, the potential saving from fewer spray applications for codling moth was reduced by the continued need to apply other farm chemicals on the same dates. Conversely, the balance between pests and natural enemies expected in apple orchards not sprayed with insecticides for codling moth was not found in this study. The outbreak of leafminers in all orchards in 1992 demonstrated the cyclic failure of biological control for this pest and forced the growers to spray an insecticide disrupting the natural enemies of leafminers and leafhoppers (Table 4). Severe injury to fruit by leafrollers in 1991 caused growers to treat orchards with summer applications of organophosphates in subsequent years, even when pest populations were low. It is unlikely that natural enemies can control pest populations in orchards sprayed with broadspectrum insecticides nor can they respond quickly to pest outbreaks in small, isolated pheromone-treated J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 3] orchards surrounded by sprayed orchards. Sustained biological control in tree fruit pest management evidently depends on the registration of non-disruptive tools for these sporadic and secondary pests. The level of biological control possible in apple orchards in the Yakima Valley can probably be seen best in certified organic orchards. Organic orchards cannot be treated with organophosphate, carbamate, pyrethroid, or other synthetic insecticides (Washington State Department of Agriculture 1992). During 1990, pest and natural enemy populations were surveyed in five paired organic and conventional orchards (Knight 1994). Organic orchards had significantly lower populations of aphids and leafminers than conventional orchards, and significantly higher populations of natural enemies of green aphids, leafminers, and leafhoppers. In 1990, leafrollers were not a problem in any of these orchards. However, fruit injury from codling moth was much higher at harvest in organic (0.3-32.0%) than in conventional orchards (0.1-0.9%). Mating disruption was not available in 1990 and organic growers used a seasonal average of 14 botanical and microbial insecticide sprays for codling moth (Knight 1994). Empirical analysis of these data from 1990-1993 from organic and conventional apple orchards indicates that a combination of these programs could be adopted to reduce the use of broad-spectrum insecticides and enhance the role of biological control. Mating disruption could be used to manage codling moth, and other pests could be managed either early in the season or growers could use biological control and a limited number of selective insecticides. Development, demonstration, and validation of this approach are needed in representative orchards in the Yakima Valley, as well as in each of the other major fruit producing regions in the western United States. ACKNOWLEDGEMENTS I thank John Turner and numerous summer field assistants at the USDA-ARS Laboratory, Yakima, WA, who conducted these studies and collected the data. I also thank the growers for their cooperation. This work was conducted with frequent and useful consultation with Larry Gut and Jay Brunner, Washington State University, Wenatchee, WA. Mike Willet, Washington State University, Yakima, WA contributed many useful ideas to this project. I also acknowledge the critical comments of an earlier draft by Bruce Barrett, University of Missouri, Columbia, MO, Larry Hull, Penn State University, Biglerville, PA, and Gary Judd, Agriculture Canada, Summerland, British Columbia. This work was conducted with support from the Washington Tree Fruit Research Commission. REFERENCES Alway, T. 1991. A grower's perspective. Proc. WA Hort. Assoc. 87: 204. Barnes, M. M., J. G. Millar, P. A. Kirsch & D. C. Hawks. 1992. Codling moth (Lepidoptera: Tortricidae) control by dissemination of synthetic female sex pheromone. J. Econ. Entomol. 85: 1274-1277. Barrett, B.A. & J. F. Brunner. 1990. Types of parasitoid-induced mortality host stage preferences, and sex ratios exhibited by Pnigalio flavipes (Hymenoptera: Eulophidae) using Phyllonorycter elmaella (Lepidoptera: Gracillariidae) as a host. Environ. Entomol. 19: 803-807. Brooks, T. W., C. C. Doane & R. T. Staten. 1979. Experience with the first commercial pheromone communication disruptive for suppression of an agricultural pest, pp. 375-388. Jn F. J. Ritter (ed.), Chemical ecology: odour communication in animals. Elsevier, Amsterdam. Brunner, J. F., L. J. Gut & A. L. Knight. 1992. Transition of apple and pear orchards to a pheromone- based pest management system. Proc. WA Hort. Assoc. 88: 169-175. 38 J.ENTOMOL.SOC.BRIT.COLUMBIA 92 DECEMBER, 1995 Hinman, H. R., P. Tvergyak, B. Peterson & M. Clements. 1992. 1992 estimated cost of producing Red Delicious apples in central Washington. Washington State Univ. Publ. EB1720. 12 pp. Hintze, J. L. 1987. Number cruncher statistical system. V. 5.01. Kaysville, UT. 286 pp. Howell, J. F. 1992. Two years of commercial use of Isomate-C to disrupt mating for control of codling moth. Proc. WA Hort. Assoc. 88: 176-181. Hull, L. A. & J. W. Grimm. 1983. Sampling schemes for estimating populations of the apple aphid, Aphis pomi (Homoptera: Aphididae) on apple. Environ. Entomol. 12: 1581-1586. Knight, A. L. 1992. New dimensions in mating disruption of codling moth. Proc. WA Hort. Assoc. 88: 166-168. Knight, A. L. 1994. Population densities of pests and natural enemies in paired organic and conventional apple orchards in the Yakima Valley, Washington. J. Entomol. Soc. Brit. Columbia 91: 27-36. Knight, A. L., J. F. Brunner & D. Alston. 1994. Survey of azinphosmethyl resistance in codling moth in Washington and Utah. J. Econ. Entomol. 87: 285-292. Moffitt, H. R. & P. H. Westigard. 1984. Suppression of the codling moth (Lepidoptera: Tortricidae) population on pear in southern Oregon through mating disruption with sex pheromone. J. Econ. Entomol. 77: 1513-1519. Ott, S. L., C. L. Huang & S. K. Misra. 1991. Consumers’ perception of risk from pesticide residues and demands for certification of residue-free produce. pp. 175-188. Jn J. A. Caswell (ed.) Economics of food safety. Elsevier, New York. Pfeiffer, D. G., W. Kaakeh, J. C. Killian, M. W. Lachance & P. Kirsch. 1993. Mating disruption for control of damage by codling moth in Virginia apple orchards. Entomol. Exp. Appl. 67: 57-64. Pimental, D., H. Acquay, M. Bittonen, P. Rice, M. Silva, J. Nelson, V. Lipner, S. Giordano, A. Horowitz & M. D'Amore. 1992. Environmental and economic costs of pesticide use. BioScience 28: 778-784. Prokopy, R. J. & B. A. Croft. 1994. Tree fruit pest management, pp. 214-231. In R. L. Metcalf & W. H. Luckman (eds.) Introduction to pest management. John Wiley & Sons, NY. Varela, L. G., S. C. Welter, V. P. Jones, J. F. Brunner & H. Riedl. 1993. Monitoring and characterization of insecticide resistance in codling moth (Lepidoptera: Tortricidae) in four western states. J. Econ. Entomol. 86: 1-10. Washington State Apple Commission. 1993. Gallup poll on consumer attitudes toward Washington State apples. Wenatchee, WA. 18 pp. Washington State Department of Agriculture. 1992. Certification of organic foods. RCW 15.86.060. Washington State University Cooperative Extension Service. 1992. Spray guide for tree fruits in eastern Washington. Washington State Univ. Ext. Bull. 0419. 156 pp. Williamson, E. R., R. J. Follwell, A. Knight & J. F. Howell. 1994. Economic analysis of codling moth control alternatives in apple orchards. WA State Coop. Ext. EB 1789. 12 pp. Weissling, T. J. & A. L. Knight. 1995. Vertical distribution of codling moth adults in pheromone-treated and untreated plots. Entomol. Exp. Appl., in press. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 39 A sequential sampling system for the white pine weevil, Pissodes strobi (Coleoptera:Curculionidae) RENE I. ALFARO PACIFIC FORESTRY CENTRE, CANADIAN FOREST SERVICE, 506 WEST BURNSIDE ROAD, VICTORIA, BC V8Z 1MS5 ABSTRACT A sequential sampling system is described for determining degree of infestation by the white pine weevil, Pissodes strobi, in stands of spruce, Picea spp. The method requires that a maximum of 60 trees be randomly selected in sequence and that the cumulative number of infested trees be plotted against the total number of trees sampled. Sampling is stopped as soon as decision lines calculated for < 10% infestation or >20% infestation are crossed. Key words: spruce, Picea spp., monitoring, pest management INTRODUCTION The white pine weevil, Pissodes strobi Peck, is a serious pest of reforestation and natural regeneration, causing severe damage to Sitka spruce, Picea sitchensis (Bong) Carr., Engelmann spruce, Picea engelmannii Parry, white spruce, Picea glauca (Moench) Voss, and their hybrids, in British Columbia. This weevil is widely distributed in North America, being found in most provinces of Canada and in many states of the Union. The hosts attacked in eastern North America include eastern White pine, Pinus strobus L., Jack pine, Pinus banksiana Lamb., and Norway spruce, Picea abies (L.) Karst. P. strobi adults overwinter in the duff (Silver 1968), usually near the tree from which they emerged in the previous fall. Early in the spring (late March, April), adults fly or Crawl to the terminal leader of host trees and commence feeding and mating. Oviposition begins soon after. Eggs are laid near the tip of the leader, just under the apical bud, in feeding punctures which are then covered with a fecal plug. After hatching, the larvae orient downwards and begin consuming the phloem. As their galleries merge, the larvae form the characteristic "feeding ring", in which larvae move downwards in synchrony, consuming all phloem around the circumference of the leader. This causes the girdling and destruction of the leader. Pupation takes place in chambers excavated in the xylem and covered with wood fibers. New adults emerge from late July to September. After emergence, these fall adults feed for a while, disperse, and when temperatures drop and photoperiod shortens, they go into hibernation in the duff. Effective pest management programs for the white pine weevil (Alfaro et a/. 1995) require regular monitoring in order to determine if existing insect populations and damage levels are at or near levels requiring treatment. Post-treatment assessments are also required to determine the efficiency of control measures. The theory of sequential sampling was developed during World War II for use in quality control and in the 1950's it began to be applied to forest pest control decisions (Waters 1955). Regular sampling methods usually require a fixed number of samples that 40 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 will estimate a level of infestation to a desired level of precision. However, for the same precision, the specified number of samples will invariably be inadequate at low and excessive at high pest densities. Sequential sampling is a system designed to simply choose between two alternatives: is the density of the pest or the level of damage higher or lower than a given critical level? Sampling continues only until results indicate that one alternative is more likely than the other at some constant, acceptable level of probability. When infestations are very high or very low, the most likely alternative becomes apparent very quickly. Hence savings of up to 50% in time and cost of sampling can be achieved (Onsager 1976). : The objective of this paper was to report a sequential sampling system developed for the rapid assessment of white pine weevil infestations. MATERIALS AND METHODS The sampling system reported here was developed following the formulae indicated by Waters (1955). Infestations by the white pine weevil will be classified as light if the proportion of trees with current weevil damage is less than 10% (H)) and severe if 20% (H,) or more of the trees are attacked. Damage levels between 10 and 19% are termed moderate. These thresholds were based on practical considerations: estimates of merchantable volume at rotation, assuming infestations lasting 20 years, at the above thresholds, indicate losses of 13 and 21%, respectively (Alfaro 1994). Infestations below 5% of the trees/year are thought to represent endemic levels. The sampling plan developed here calls for examining sufficient trees until cumulative results indicate that either hypothesis H, or H, is more likely to be correct at some pre-established degree of reliability. As in regular sampling, the specified degree of reliability will determine, to a large extent, the feasibility of the survey in terms of logistics and costs. For the sampling method reported here, both probability of Type I error (probability of accepting H, when Hi is true) as well as for Type II error (probability of accepting H, when H, is true), were set to 10% (i.e. a = B = 0.10). We use the operations for the binomial distribution reported by Waters (1955) to find the slope and intercepts of the parallel decision lines. Intercepts: oe = oe? oa eo log la Aah Dine Ps Where o and f are the established probabilities for Type I and II errors and p, and p> are the classification thresholds of 10 and 20% infestation. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 41 RESULTS AND DISCUSSION The following equations were calculated for the upper and lower decision lines (Fig. 1): dj =0.145n + 2.71 dz = 0.145n - 2.71 | Severe >= ene do sane tH ETT SYARUAVAMASONATOUANAMAATATNGEAHAEDE=2 MITT uae ETE ere [tight < 10% | | | | | SA TE Va RN tat eee UT 0 5 10 15 20 25 30 35 40 45 50 ss 60 Total No. of trees sampled (n) Cumulative No. trees infested (ep) (@) (@) Figure 1. Parallel decision lines for a sequential sampling system for the white pine weevil, Pissodes strobi Stands are classified as severely infested (>=20% of the trees attacked) if a plot of the cumulative number of attacked trees versus the total number of trees sampled crosses the upper line. Stands are classified as light (<10%) if the lower line is crossed. If after sampling 60 trees (see below) neither of the lines is intercepted, the stand is labeled as moderately infested (10-19% attack), The reliability of this sampling system can be evaluated by examining the Operating Characteristic (O.C.) curve (Waters 1955) which indicates, for any infestation level, the probability of correctly classifying an infestation as light (Fig. 2). The probability of labeling a stand as light drops sharply when stands have higher than 10% infested trees. 1 c= Operating characteristic curve (OC) 0.9 Probability ro) ol 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 Proportion of sample trees infested (p) Figure 2. Probability (p) of classifying a stand as light for different degrees of infestation 42 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 The number of samples required to reach a decision can be evaluated by calculating the Average Sample Number (A.S.N.) curve (Waters 1955), which gives the number of samples that will, on the average, result in acceptance of either H, or H, for any level of infestation (Fig. 3). The A.S.N. allows us to realize the efficiency of this sequential sampling system. An uninfested stand will be identified after 19 sequential random samples without weevil attack (the X intercept in Fig. 1). A 100% infested stand (an unlikely situation) could be identified by finding only three infested trees in sequence (the Y intercept in Fig. 1). The largest number of samples (60) required to reach a decision occurs when the infested stand has between 10 and 19% infestation. If no decision has been reached after examination of 60 trees, the stand must be declared “Moderately infested”. Average sample number (ASN) 60 " “i \ o oO b oO Average No. sample trees © io) (o) jo) io) oO So (=) (e) (oe) [o) S = x m < im 2 > © o ° © © jo) © io) o i>) jo) © ie) - Proportion of sample trees infested (p) Figure 3. Average number of sample trees examined to reach a decision in stands with different degrees of infestation (p). FIELD APPLICATION. One of the major drawbacks of sequential sampling in forestry is the requirement that trees are sampled at random and in the sequential order in which they were selected. This would result in an inefficient criss-crossing of the stand in order to maintain the sequence. I suggest that, in the office, the area of the stand be divided into a grid of X,Y coordinates (e.g. a 5m x 5m grid). Then, using a random number table or a packaged software program, select 60 random X,Y coordinates in the stand, keeping track of the sequential order of selection, i.e. 1 to 60. Divide the list into two groups: coordinate points numbered 1-30 and 31-60. Sample all trees in the first group as you move through the stand in the most efficient manner, i.e., without regard to the sequence, using a compass and measuring tape to locate the tree nearest to the selected X, Y coordinate. After sampling the first group, plot the cumulative number of attacked the decision lines have been crossed, stop sampling and record the stand as lightly or severely infested. If after 30 samples the cumulative attack line is still in the intermediate zone, sample the entire second 30-tree group, in the most efficient manner. At the end of this second pass through the stand, add to the cumulative plot drawn for the first group, keeping the sequential order of selection. This sequential plot will have either crossed one of the decision lines, or remained in the intermediate zone, causing the stand to be J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 43 classified as light, moderately or severely infested. It is anticipated that lightly or severely infested stands will be identified in the first pass. Moderately infested stands will require two passes, i.e. the sampling of the entire 60-tree sample. It is expected that this method will result in significant time saving when classifying stands for treatment. REFERENCES Alfaro, R.I. 1994. The white pine weevil in British Columbia: Biology and damage. pp 7-22 in, R.I. Alfaro, G.Kiss and R. Gerry Fraser (eds.). The white pine weevil: biology, damage and management. Proc. of a Symp. held Jan. 19-21, 1994, in Richmond, B.C. FRDA Rep. 226. Can. For. Serv. Victoria, B.C. Alfaro, R.I., J.H. Borden, R.G. Fraser, and A. Yanchuk. 1995. The white pine weevil in British Columbia: Basis for an integrated pest management system. For. Chron. 71: 66-73 Onsager, J. 1976. The rationale of sequential sampling, with emphasis on its use in pest management. U.S. Dep. Agric. Res. Serv. Tech. Bull. 1526, 19 pp. Silver, G.T. 1968. Studies on the Sitka Spuce weevil, Pissodes sitchensis, in British Columbia. Can. Entomol. 100: 93-110. Waters, W.E. 1955. Sequential sampling in forest insect surveys. For. Sci. 1: 68-79. y WA is ih J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 45 Range of gypsy moth in British Columbia: a Study of climatic suitability ALISON F. HUNTER DEPARTMENT OF BIOLOGY, DALHOUSIE UNIVERSITY, HALIFAX, N.S. B3H 4J1" and B. STAFFAN LINDGREN FACULTY OF NATURAL RESOURCES AND ENVIRONMENTAL STUDIES, UNIVERSITY OF NORTHERN B.C., 3333 UNIVERSITY WAY, PRINCE GEORGE, B.C. V2N 4Z9 ABSTRACT The potential range of gypsy moth in Bntish Columbia 1s predicted from climatic comparisons to its native range in Eurasia and by using temperature- dependent phenological models of the life stages. Thecool and wet coastal areas, northem B.C., and high elevations are predicted to be unsuitable for gypsy moth. Southeastern Vancouver Island, parts of the lower mainland, and southern interior valleys appear to have suitable climates. However, the availability of preferred hosts may limit establishment in some of these areas. Habitats with Garry oak are of particular concem, since it is the most suitable native tree species and is already threatened by urban development. Keywords: Lymantria dispar, Lymantnidae, discriminant function analysis, life stage, biogeoclimatic zones, development modelling INTRODUCTION The gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), a native of Eurasia, was introduced to North America in 1869 from France (Montgomery and Wallner 1988). Despite the inability of females of the European strain to fly, it has since expanded its range from the initial foothold in Massachusetts to the entire eastern forest region from southern Quebec and Ontario to Georgia, and to Wisconsin in the west. Individuals have been caught in western North America since the late 1970s, when pheromone traps were first developed and used. Moths have been trapped in Oregon, Washington, Utah, California, and British Columbia. An outbreak in Oregon in 1984, and local populations in Oregon, Washington and Utah, were all controlled with Bacillus thuringiensis. In B.C., all introductions so far have died out naturally or been controlled by spraying. Its potential to become established in B.C. is a controversial but pressing question. The major mode of introduction is as egg masses, for example on recreational vehicles and trailers from infested areas in eastern North America. With increasing immigration and tourism from the east to B.C. and the abandonment of control efforts in Quebec and Ontario, introductions may continue at high levels in the future. The range of gypsy moth depends on adequate climate for the annual cycle of development and synchronization ' Current address: Department of Biology, Mormill Science Center, Box 35810, Univ. of Massachussetts, Amherst, MA 01003-5810 46 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 with hosts, and on the availability of suitable hosts. The gypsy moth is remarkably polyphagous, but its best development is on oaks and some poplars or aspen. The suitability of many of the woody plants of B.C. for gypsy moth has not been assessed. However, Garry oak, quaking aspen, and red alder are all favourable (Lechowicz and Mauffette 1986, Miller et a/. 1991a). Larvae develop successfully on Douglas-fir, lodgepole pine and ponderosa pine in the laboratory, although development is slow, and larval survival is highly dependent on temperature and foliage age (Miller and Hanson 1989, Miller et a/. 1991b). First instar larvae were unable to establish on Douglas-fir in another laboratory study (Jobin 1981). The objective of this paper is to predict the potential range of gypsy moth in B.C., and identify areas of high susceptibility. We have used several approaches to accomplish this, but we have limited the analysis mostly to climatic factors. Hosts are considered only briefly. The life cycle of the gypsy moth The gypsy moth is univoltine, with an obligate winter diapause (Montgomery and Wallner 1988). The moths emerge in mid-summer (July in eastern North America and Europe). Females from Europe are flightless and emit a pheromone to attract males. Eggs are laid near the site of pupation which is usually on tree trunks or the undersides of branches, but also on rocks or man-made structures. All eggs are laid in a single mass covered with short hairs from the female’s body. The embryos develop for about two weeks (depending on temperature), and the larvae overwinter within the eggs. In spring, around the time of budburst of the favoured oak hosts, the larvae hatch. Newly-hatched larvae climb upwards to locate food; if they are unsuccessful they will spin silk strands to be wind-blown (ballooning) to another tree. Early instar larvae feed during the day but the later instars feed at night, seeking sheltered spots to hide during the day. They may move between trees, especially if their original host tree is defoliated. Typically, larval development takes from six to eight weeks, with five instars in males, and six in females. Mature larvae seek protected spots for pupation, usually in crevices near the tree base, in the litter, or on rocks or structures, and emerge as adults about two weeks later. Range of gypsy moth in Eurasia and eastern North America The gypsy moth is native to most of Europe, northern Asia, Japan and China (Giese and Schneider 1979). In Europe, it occurs from the west coast to the Urals; extending north to a line from about central Sweden, east to Moscow, roughly corresponding to the northern limit of the range of oaks, its favoured hosts (Giese and Schneider 1979). In altitude it is found also as high as oaks will grow (Gnjpma, 1989). The southern limit is in northern Africa and the islands of Corsica and Sardinia. Grijpma (1989) noted that gypsy moth is most abundant in the broadleaved forests of southern and southeastern Europe. MATERIALS AND METHODS We used several methods to predict the suitability of the regions of B.C. for establishment of gypsy moth, focusing on climatic parameters. First, we studied the climates in regions of Europe and Japan where the gypsy moth occurs, and those of neighbouring areas where it is absent, and compared them to the climates of British Columbia. We analysed the climatic limits in Eurasia with two-dimensional plots, and also used multivariate analyses. As well, we ran temperature-dependent models of gypsy moth development on climatic data from selected sites in B.C., to see whether gypsy moth can complete all its life stages in these climates. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 47 Plotting of climatic limits The gypsy moth ranges in Europe and Japan were extracted from the maps of Giese and Schneider (1979). Distribution records in Asia other than those of Japan were not considered to be reliable, so data for Asia were not included in the analysis. Climatic normals (30 year means) were obtained from Muller (1982) for stations in Europe, Japan, and North America, and from Environment Canada, Atmospheric Environment Service, for B.C. The normals for stations where gypsy moth occurs and those bordering on the range were plotted. Temperature and precipitation data for weather stations, in areas with and without gypsy moth, were plotted for comparison with B. C. weather stations. Mapping of biogeoclimatic sub-zones The biogeoclimatic classification system in British Columbia combines vegetation, soil, and climatic data to characterize forest and range ecosystems (Pojar et al. 1991). Climatic summaries (mean temperatures for warmest and coldest months, mean annual temperature, and mean annual precipitation) for biogeoclimatic sub-zones were matched with climatic limits for the gypsy moth as determined by Giese and Schneider (1979). Biogeoclimatic subzones with climatic characteristics where the gypsy moth might become established (precipitation >100 mm/year; mean Jan. temperature -18 to +12 °C; and mean July temperature +15 to +27 °C), and where the potential for outbreaks may exist (precipitation 250 - 1000 mm/year; mean Jan. temperature -18 to + 5 °C; mean July ‘temperature +15 to + 23 °C), were plotted to outline potential climatic boundaries in B.C. Discriminant functions The above method can consider only two variables at a time, but climate is composed of many variables. We used discriminant functions to get a better idea of the multivariate influence of climate on the range of the gypsy moth. The discriminant function technique finds the best linear combination of variables for discriminating between two or more classifications, in this case the presence vs. absence of gypsy moth. The function can then be used to classify new observations, in this case sites in B.C. Variables used were Jan. and July mean monthly temperatures, average annual precipitation and temperature, July minus Jan. temperature (an index of continentality), and precipitation divided by July temperature (an index of dryness). The DISCRIM procedure of SAS was used (SAS Institute, 1985). The discriminant functions based on 139 European, Japanese and eastern North American stations in and around the current range of gypsy moth distribution were used to classify 55 sites in B.C. and the Pacific Northwest as to their climatic suitability for gypsy moth. Life stage development modelling The rate of growth of an insect depends on various factors, including food quality, population density, pathogen infection, and humidity (e.g. Lance et a/. 1986, 1987), but temperature is the major determinant. As a minimum requirement for establishment, temperatures must be warm for long enough for the insect to complete all life stages from egg to adult. In B.C., climatic conditions vary considerably from the wet and cool coastal climate, to the hot and dry summers and cold winters of the interior. These temperature variations may define the potential range of the gypsy moth in B.C. The timing of spring emergence is crucial because it is the starting point for the other Stages. We predicted spring emergence using the biophysical model of Hunter (1993), which gave the most accurate prediction of hatch phenology in 3 out of 4 years of data from Quebec, out of three models tried (Hunter 1993). The program of Sheehan (1992) was used to simulate gypsy moth larval and pupal development. We ran these models for Victoria, Vancouver, Castlegar, Williams Lake, Prince Rupert, Smithers, Prince George and Fort St. John. These sites had relatively complete 48 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 30-year weather records and are representative of east-west and north-south gradients in the province. The model was mun for five years, chosen as follows: 1) The years with the - lowest and highest average temperatures in the months Jan. to May were determined. Out of these, the years having the earliest and latest hatch were chosen based on the egg hatch model of Hunter (1993). 2) In addition, the years having the warmest and coldest average May temperatures were chosen, and 3) the year 1992, which was frequently among the warmest years, was chosen to give a standard across sites that was near to a best case for the gypsy moth. These years represented the best and worst years for gypsy moth development. Since the rate of development varies with host species, the model has several host plant options. We ran the model with all larvae feeding on red oak, a common Vancouver street tree. The rate of development on this host is slightly less rapid than on white oak, but more rapid than on most other hosts (Casagrande ef al. 1987). To validate the model, we compared predicted adult emergence times with available data on the timing of adult male moth catches in traps in the Vancouver area in 1991- 1993, and in the east Fraser Valley in 1994. We used records of live moths found in detection traps by Agriculture Canada, with the assumption that moths would not survive for more than a few days once captured in a trap. RESULTS Plotting climatic limits Plots of climate data showed that mean annual temperatures of 3 °C (Fig. 1) and Jan. temperatures of -15 °C (not shown) appear to limit the gypsy moth in the north. Only two stations with gypsy moth "present" had a mean July temperature below 15 °C (Brocken, Germany, and Botrange, Belgium; Fig. 2). The resolution of the maps of Giese and Schneider (1979) is not fine enough to determine whether or not these cold pockets (which are surrounded by warmer areas) actually have gypsy moth. There are some areas where gypsy moth does not occur although it occurs at sites with similar climates (mean annual temperatures of 3 - 10 °C, Fig. 1; mean July temperatures of 15 - 18 °C, Figure 2). These sites are in the United Kingdom, Norway, Sweden and Finland, beyond the range of oaks, but within the ranges of aspen and alder which are potential hosts. The European distribution of gypsy moth closely matches the range limits of oaks. Most B.C. sites fall into this climatic range, in which the presence of oaks seems as important as climate. All of the sites in eastern North America with gypsy moth are within the same range of temperature and precipitation as the areas in Eurasia where gypsy moth occurs (Fig. 1 and 2). However, B.C. stations with low temperatures, and extremely high or low rainfall, are outside this range. Few places receive as much precipitation as coastal B.C. (>1000 mm per year). Similar amounts occur on the Atlantic coast of Europe (Ireland and Norway), in some coastal areas of former Yugoslavia, and in Japan. The gypsy moth has not been recorded from Ireland or Norway. Outbreaks have occurred in Yugoslavia, but the resolution of Giese and Schneider's (1979) map is not high enough to determine whether these have occurred in the wet areas or in the dry Mediterranean climates of the coast. The gradient of precipitation is very steep in this area. Japan receives at least as much precipitation as coastal B.C. (Fig. 2), and the gypsy moth is present in the south of Japan, with outbreaks in the northwest and on Hokkaido. However, compared with coastal B.C. the climate in Japan is much warmer in the summer (Fig. 2), and oaks occur as important forest elements throughout the Japanese archipelago. Another difference is that this is the Asian strain of the gypsy moth, which has slightly different development rates and hosts. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 49 20 > Areas with GM Mean Annual Temperature® C 128 256 512 1024 2048 4096 8192 128 256 512 1024 2048 4096 8192 Mean Annual Precipitation (mm) Figure 1. Annual mean temperature versus total precipitation for sites: A) with gypsy moth in Europe, Japan and North America, and without gypsy moth in Europe; and B) at 51 sites in British Columbia and 4 sites in the Pacific Northwest United States. The dashed line in A) encloses sites with gypsy moth in Europe, Japan, and North America (two cold outliers in Europe excepted, see text). The same lines have been superimposed on the data in B) for reference. 30 With GM A Turgal, Russia V.9~ 25 20 GM 15 Mean July Temperature °C Botrange, Belglum A<—«Brocken, Germany 128 256 512 1024 2048 4096 8192 128 256 512 1024 2048 4096 8192 Mean Annual Precipitation (mm) 10 Figure 2. July mean temperature vs total precipitation for sites: A) with gypsy moth in Europe, Japan, and North America, and without gypsy moth in Europe; and B) at 51 sites in British Columbia and 4 sites in the Pacific Northwest United States. The solid line in _ A) encloses sites without gypsy moth in Europe. Areas with gypsy moth in Europe, Japan, _ and North America (two cold outliers in Europe excepted) are above and to the right of _ the dashed line. The same lines have been superimposed on the data in B) for reference. 50 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Biogeoclimatic sub-zone Figure 3 shows the results of mapping biogeoclimatic sub-zones with suitable climate based on Giese and Schneider’s (1979) climatic limits for gypsy moth. This analysis shows that gypsy moth can establish in most of the southern part of British Columbia, with the exception of higher elevations and the wet coastal areas. Climatic conditions conducive to outbreaks exist in the Lower Mainland and the dry coastal areas immediately to the north of Vancouver,-B.C. (the Sunshine Coast), the dry areas (east coast) of southern Vancouver Island, and the dry and warm valleys of the southern interior (Okanagan Valley and the Kootenay areas). a * SARE 2 alae Beeately et i} }s rer woe ee Risk of establishment Risk of outbreak Figure 3. Areas at risk for establishment, or outbreak, respectively, of gypsy moth in B.C., based on plotting of biogeoclimatic subzones of B.C. and climatic range limits for the gypsy moth reported in the literature (Giese and Schneider 1979). Map courtesy of Forest Insect and Disease Survey, Pacific Forestry Centre, Canadian Forest Service, Victoria, B.C. Discriminant function analysis Discriminant function analysis showed that many areas of southern and central B.C. have climates very similar to those of Europe and Japan where gypsy moth is present (Fig. 3). Figure 4 shows a graphical representation of the results of this analysis, so that each weather station is represented as a dot, the size of which represents the discriminant function prediction of its climate’s relative suitability for gypsy moth. In addition, Fig. 4 shows geographic locations where gypsy moth has been detected using pheromone trapping (triangles). Northern sites in B.C., and cool, wet sites of central and western B.C. are similar to sites in Europe that lack gypsy moth. The functions misclassified 26 (17%) of the original 156 sites, including Brocken, Germany; Botrange, Belgium; and Turgaj, north of the Aral Sea in the former USSR J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 51 (Fig. 2). Thus, we can expect a similar error rate in B.C. Three of the four sites classified in the Pacific Northwest United States had a climate very suitable to gypsy moth. These were Medford, OR (similarity index of 0.99), Portland OR (0.96), and Seattle, WA (0.93). The fourth site (Tatoosh Island, at the extreme northwest tip of the Olympic Peninsula, WA) was classified as unsuitable (0.37). ¢ a < ALBERTA fy VANCOUVER “% ISLAND Figure 4. Graphical representation of the discriminant function analysis. Each weather station is represented by a dot, the size of which represents the discriminant function prediction of its climate’s suitability for gypsy moth. The solid line encloses the subset of weather stations with climates very suitable for gypsy moth at lower elevations (cf. Figure 3, biogeoclimatic subzones with climate suitable for outbreaks). The triangles show locations where gypsy moth life stages have been found in B.C. Life stage development modelling Validation of Lower Mainland trap catch data. The models predict when adults emerge from pupae, and adults can be expected to live for several days. Thus, the actual catches can be expected to lag a couple of days or so behind the predicted emergence period. The model gave a remarkably good correspondence between predicted and observed phenologies, given that the flight time varies by up to a month among years, and considering the very small numbers of live moth catches (Table 1). Ability to complete development. The temperature-dependent models predict that gypsy moth will be able to reach the adult stage in all years at the more southern locations, but not in every year in the northern ones. In northern B.C. few individuals complete development even in the warmest years (Table 2). These models do not provide for the requirement that there must be sufficient warmth between the time that eggs are laid and winter begins for the embryos to develop into larvae. This is an additional constraint, so even if adults could emerge and mate in the fall, there may well be insufficient warmth for this embryonic development. 52 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Table 1 Comparison of timing of catches of male gypsy moths found alive in traps on the Southern Mainland of British Columbia to predicted time of emergence of adults using 2 models (Sheehan 1992, Hunter 1993). Adults live for a few days after emergence. Location Vancouver Vancouver Vancouver Chilliwack Hope Period of gypsy moth flight Year Observed from trap catches 1991 7 Aug. - 4 Sept. (N=20) 1992 9 July - 10 Aug. (N=26)* 1993 3 Aug. - 25 Aug. (N=13) 1994 27 July, 5 Aug., 10 Aug. (N=3) 1994 3 Aug., 5 Aug. (N=2) Predicted emergence 5 Aug. - 31 Aug. 17 July - 10 Aug. 29 July - 24 Aug. 19 July - 12 Aug. 21 July - 14 Aug. *One additional live moth was caught on 25 Aug. Table 2 Predicted ability of gypsy moth to complete development at selected sites in B.C. in years with extreme climatic conditions and in 1992, which was among the warmest years at all sites. The table lists the most advanced stages attainable (A = Adult, P = Pupa), and the date when moths begin to emerge from pupae. All individuals did not necessarily achieve the most advanced stage before the onset of winter. Development Stage Reached and Date of First Flight in Year (with) Location Coldest Warmest Earliest Latest 1992 May May hatch hatch Victoria A-Aug28 A-Jul20 A-Jul22 A-Aug27 A-Jul22 Vancouver A-Aug28 A-Jull10 A-Jul29 A-Aug28 A-Jul17 Castlegar A-Aug3 A-Jul22 A-Jull4 A-Aug2 A-Jull4 Williams Lake A - Oct 2 A-Sepl12 A-Augl4 A-Sepl16 A-dAug 14 Smithers P A-Augl2 A-Aug30 A-Sep25 A-Aug3l Prince Rupert P A - Oct 8 A - Oct 8 P P Prince George P A-Augl13 A-Augl3 P A - Aug 13 Fort St. John P A-Aug21 P P A - Aug 21 In summary, Castlegar, Victoria, and Vancouver are suitable for complete development; Williams Lake, Smithers, and perhaps Prince George, are marginal; while Prince Rupert and Fort St. John would probably not permit complete gypsy moth development. DISCUSSION The results of the climatic analysis, the multivariate comparisons of the weather in European and Japanese sites, and the gypsy moth development models gave similar predictions: southern and central B.C. have climates suitable for the gypsy moth; northern areas, high elevations, and the cool, wet coastal areas are unsuitable. However, climate is not the only factor affecting the establishment of gypsy moth in B.C. Hosts are important, and the largely coniferous forests of B.C. may be quite resistant. Our analyses indicate that gypsy moth may not become established where there are no oaks, even if the climate is suitable, as seems to be the case in north-western Europe. The only native oak in B.C., Garry oak or western white oak (Quercus garrayana), is limited to the Gulf Islands and southeastern coastal Vancouver Island from the southern tip to Comox, plus J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 53 two small patches in the lower mainland (Lyons 1991). Ornamental oaks are common in urban and suburban areas, where introductions are most likely to occur. Areas in the southern mainland, eastern Vancouver Island and Gulf Islands with preferred hosts and suitable climate and large numbers of people moving through them are probably at the greatest risk for gypsy moth establishment. Most catches of gypsy moth have been made in these areas (Figure 4). This pattern is also evident in Oregon and Washington: most catches are made in suburban areas or places with a large component of oak (Dreistadt and Dahlsten 1989). We have included areas in Japan in the climatic analysis, although the Asian strain of the gypsy moth probably has different thermal requirements. We included these areas because it is more conservative to do so than to exclude them; including them gives the gypsy moth a larger potential range. However, the models of development are based on the European strain only. Some other influences not examined here are: synchrony with plant phenology; negative effects of rain after hatch; and freezing after the breaking of winter dormancy. Gypsy moth larvae emerge from winter dormancy around the time of leaf emergence of oaks (Hunter and Lechowicz 1992; Hunter 1993). New foliage is preferred, since it is higher in nitrogen and water, and less tough (Hunter and Lechowicz 1992). Emergence at the correct time is important because there is a brief window between budburst and the time when foliage becomes unacceptable. Gypsy moth host-seeking activities (crawling up tree trunks, ballooning) are inhibited by cool and wet weather (Leonard 1971). Phenological models for tree budburst have not been developed for hardwoods of the Pacific Northwest, and there are few data on budburst for B.C., so we could not test whether gypsy moth would be well synchronized with leaf emergence in this region. Preliminary analyses using tree phenology models from eastern North America which we applied to climatic data from B.C. indicated good synchrony (Hunter, unpublished). However winter dormancy is the least well understood life stage of the gypsy moth and of the host trees. New models are being developed that encompass the entire diapause period and should yield better predictions of gypsy moth emergence times (Gray et al. 1991). However, using a "pre-release" version of this new model altered hatching dates by only one or two days, if at all, and did not have a dramatic impact on the predictions here (Hunter, unpublished). Some further research may be worthwhile on host suitability for the most common B.C. forest and urban trees. Development rates are often slower on hosts other than oak, so the interaction betweenclimate and host needs to be considered, particularly in marginal areas where the time available for development is limited. Also, although gypsy moth can survive on many species in the lab, they may avoid feeding or do much more poorly on these hosts in the field. This may be due to factors such as: unacceptably low quality of foliage during the host-seeking stage (Hunter and Lechowicz 1992); differential susceptibility to disease (Keating and Yendol 1987); mortality from predators on hosts where growth is slow, and lack of suitable day-time resting sites (Liebhold ef al. 1986). This is not the first effort to predict where gypsy moth will be able to establish. Giese and Schneider (1979) developed climatic limits in Europe and Asia using a cartographic comparison between isotherms and isohyets with the range of gypsy moth. Allen ef al. (1993) developed predictions for Florida and for the entire world. Their world predictions, based on climate matching, seemed to indicate the potential for establishment of gypsy moth in southwestern B.C., but not northern Vancouver Island or Prince Rupert, and thus matched our more detailed projections for B.C. Sullivan and Wallace (1972) 54 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 examined the cold tolerance of overwintering gypsy moth eggs. They found that eggs can withstand several weeks exposure to -18 °C, and a few days below -24 °C with no reduction in survival. Snow cover provides effective insulation for egg masses laid close to the ground, so they can survive much lower air temperatures. Sullivan and Wallace (1972) predicted that the distribution of host plants would be more significant in determining northern range limits than would low winter temperatures. The range of the gypsy moth in eastern North America is apparently still expanding northward in Ontario (but not in Quebec, as far as is known) and it remains to be seen whether they will persist beyond the range of oaks. | In B.C. the most vulnerable area will be the range of Garry oak. Since this area is already threatened by urbanization, and Garry oak populations are declining, the potential impact of gypsy moth, should it establish itself there, is of great concern. Monitoring and education of landowners should be greatest in this area. Two additional areas are of less certain susceptibility to gypsy moth. The southern mainland has suitable climates, particularly in the drier parts, and a variety of ornamental hardwoods that may provide suitable hosts. However, gypsy moth populations may not be able to persist in urban settings with little input from surrounding continuous hardwood forests. For persistence, Allen et a/. (1993) estimated that a gypsy moth population requires a minimum patch size of 1.06 km diameter of continuous, suitable forest. Diffusion from smaller patches would be greater than reproduction within the patch, so populations would decline. In any case, in urban and suburban areas, gypsy moth would mostly be a “picnic problem" and is unlikely to threaten forestry or conservation. The other suitable areas, the dry interior valleys, should be monitored carefully, although lack of favoured hosts and spraying in orchards are likely to limit the impact of the gypsy moth. We hope that these predictions will provide a useful guideline for determining areas where monitoring and protection efforts should be concentrated. ACKNOWLEDGEMENTS This research was supported in part by a contract from the B.C. Ministry of Forests to Phero Tech Inc. We acknowledge permission from the B.C. Forest Service to use their data, and H.R. MacCarthy for reviewing the manuscript. AFH was supported by a Killam post doctoral fellowship during the final writing. N. Parfett, Natural Resources Canada, Forest Insect and Disease Survey, provided assistance with developing GIS-based maps of biogeoclimatic sub-zones. REFERENCES Allen, J. C., J. L. Foltz, W. N. Dixon, A. M. Liebhold, J. J. Colbert, J. Régniére, D. R .Gray, J. W. Wilder, and J. Chnstie. 1993. Will the gypsy moth become a pest in Florida? Florida Entomol. 76:102-113. Casagrande, R.A., J.A. Logan and W.E. Wallner. 1987. Phenological model for gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), larvae and pupae. Environ. Entomol. 16:556-562. Dreistadt, S.H., and D.L. Dahlsten 1989. Gypsy moth eradication in Pacific coast states: History and evaluation. Bull. Ent. Soc. Amer. Summer 1989: 13-19. Giese, R. L. and M. L. Schneider. 1979. Cartographic comparisons of Eurasian gypsy moth distnbution Lymantria dispar L., Lepidoptera: Lymantnidae. Entomol. News 90:1-16. Gray, D.R., J.A. Logan, F.W. Ravlin, and J.A. Carlson. 1991. Toward a model of gypsy moth egg phenology: Using respiration rates of individual eggs to determine temperature-time requirements of prediapause development. Environ. Entomol. 20:1645-1652. Gnjpma, P. J. 1989. Overview of research on Lymantnids in Eastern and Western Europe, pp. 21-50 in W. J. ENTOMOL. SOc. BRIT. COLUMBIA 92, DECEMBER, 1995 55 E. Wallner and K.A. McManus, (eds.) Proceedings, Lymantnidae: A comparison of features of New and Old World tussock moths. USDA Gen. Tech. Rep. NE-123. Hunter, A. F. 1993. Gypsy moth population sizes and the window of opportunity in spring. Oikos 68:531- 538. Hunter, A. F. and M. J. Lechowicz. 1992. Foliage quality changes during canopy development of some northern hardwood trees. Oecologia 89:316-323. Jobin, L. 1981. Observations on the development of the gypsy moth, Lymantria dispar (L.) on Douglas-fir, Pseudotsuga menziesii and western hemlock, Tsuga heterophylla. Can. For. Serv. Res. Notes 1:29-30. Keating, S. T. and W.G. Yendol. 1987. Influence of selected host plants on gypsy moth (Lepidoptera: Lymantriidae) larval mortality caused by a baculovirus. Environ. Entomol. 16:459-462. Lance, D.R., J.S. Elkinton, and C.P. Schwalbe. 1986. Components of density-related stress as potential determinants of population quality in the gypsy moth (Lepidoptera: Lymantnidae). Environ. Entomol. 15:914-918. Lance, D.R., J.S. Elkinton, and C.P. Schwalbe. 1987. Microhabitat and temperature effects explain accelerated development during outbreaks of the gypsy moth, (Lepidoptera: Lymantnidae). Environ. Entomol. 16:202-205. Lechowicz, M. J. and Y. Mauffette, 1986. Host preferences of the gypsy moth in eastern North America versus European forests. Rev. D'Entomol. du Quebec 31: 43-51. Liebhold, A. M., J.E. Elkinton and W. E. Wallner 1986. Effect of burlap bands on between-tree movement of late-instar gypsy moth, Lymantria dispar (Lepidoptera: Lymantnidae). Environ. Entomol. 15:373- 379. Leonard, D.E. 1971. Air-borne dispersal of larvae of the gypsy moth and its influence on concepts of control. J. Econ. Entomol. 63: 638-641. Lyons, C. P. 1991. Trees, shrubs, and flowers to know in British Columbia. Fitzhenry and Whiteside, Richmond Hill, Ont. Miller, J.C. and P. E. Hanson. 1989. Laboratory studies on development of gypsy moth, Lymantria dispar (L.) (Lepidoptera: Lymantriidae), larvae on foliage of gymnosperms. Can. Entomol. 121: 425-429. Miller, J. C., P. E. Hanson and D. N. Kimberling. 1991a. Development of the gypsy moth (Lepidoptera: Lymantridae) on Douglas-fir foliage. J. Econ. Entomol. 84:461-465. Miller, J. C., P. E. Hanson and D. N. Kimberling. 1991b. Development of the gypsy moth (Lepidoptera: Lymantriidae) on Garry oak and red alder in western North America. Environ. Entomol. 20:1097-1101. Montgomery, M. E. and W. E. Wallner. 1988. The gypsy moth: A westward migrant, pp. 353-375 in A.A. Berryman (ed.), Dynamics of forest insect populations. Plenum, New York. Muller, M. J. 1982. Selected climatic data for a global set of standard stations for vegetation science. Dr. W. Junk Publ., The Hague. Pojar, J., D. Meidinger, and K. Klinka. 1991. Concepts. Pp. 9-37 in D. Meidinger and J. Pojar (Eds.). 1991. Ecosystems of British Columbia. Special Report Series No. 6, B.C. Ministry of Forests, Victoria, B.C.., 330 pp. SAS Institute, 1985. SAS/STAT User's Guide Release 6.0. SAS Institute, Cary North Carolina Sheehan, K. A.1992. GMPHEN: a gypsy moth phenology model. USDA Gen. Tech. Rep. NE-158. Sullivan, C. R. and D. R.Wallace. 1972. The potential northern dispersal of the gypsy moth, Porthetria dispar (Lepidoptera: Lymantriidae). Can. Entomol. 104:1349-1355. J.LENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 57 Regional diversity of insects in the Pacific Northwest H.V. DANKS CANADIAN MUSEUM OF NATURE, P.O. BOX 3443, STATION “D”, OTTAWA, ON. 1P 6P4 ABSTRACT Provincial and state records for a sample of insect groups from Bntish Columbia, Idaho, Oregon, and Washington show that this region, here termed “the Pacific Northwest”, contains about 29% of North American insect diversity, a level that can be extrapolated to suggest that about 26,000 reported species occur in the region. Nearly half of these species are-widely distributed in North America. Many species are more- or-less broadly western; 13% of all species essentially are confined to the Pacific Northwest, although some of them occur otherwise only in Califommia, which contains many Pacific Northwestem species, especially in the north. Most of the fauna of Bntish Columbia occurs also in the United States part of the region, and one-third of the species confined in Canada to Bntish Columbia occur also in Idaho, Oregon or Washington. Despite these overall trends, there are wide differences among families and among genera, reflecting the diverse ranges, origins and ecological relationships of the different groups. Detailed studies that would more fully explain the differences are limited, even for groups of North American insects that are taxonomically better known. Nevertheless, the simple but feasible analysis of state and provincial records presented here provides useful indexes of regional occurrence, and indicates groups in the region that are of particular interest. INTRODUCTION This paper considers the diversity of the insects of the Pacific Northwest by comparing State and provincial records for selected groups within and beyond the region in North America. The nature of the data requires that entire states or provinces be included in such an analysis, and therefore the Pacific Northwest is defined here as the whole of British Columbia, Idaho, Oregon and Washington, a choice explained further below. An analysis of the insects of this region suggests patterns in the occurrence and restriction of the species there. METHODS A sample of relatively well known insect groups for which detailed state-by-state and province-by-province records or maps are available for the whole of North America was chosen for analysis. These groups, chiefly families, were selected as far as possible to represent the whole fauna (see Danks 1994b), including various taxonomic and ecological types, families from different orders, and groups represented most strongly in different parts of North America. The groups essentially are the same as those analyzed for North America by Danks (1994b), but excluding Pompilidae, for which distributional data could . not effectively be analyzed for Idaho, Oregon and Washington separately. The sample thus comprises 3322 species, or nearly 4% of the fauna of North America, estimated to be about 90,250 reported species (Danks in press). The range of each individual species was recorded by marking its occurrence in a 58 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 given region, and in the individual province or states of British Columbia, California, Idaho, Oregon and Washington, on to a standardized table of regions. Regional statistics were derived by summing the marked occurrences. Templates or transparent overlays were used to facilitate data extraction from particular combinations of columns in deriving the more complex statistics. THE PACIFIC NORTHWEST The Pacific Northwest is a convenient term for the far northwestern regions of North America, typified by relatively high rainfall and evergreen forests containing characteristic western coastal species such as Sitka spruce. Many other characteristic trees such as Ponderosa pine and Douglas fir are more widely distributed in the west. However, the wet coastal strip has some locally dry areas and it grades inland into a series of more or less complex cordilleran ranges with intervening or intermingling valleys and plateaus. Therefore, the habitats of the region are very diverse, with a considerable range in elevation and water supply, and include deserts, meadows, and aquatic, subalpine, alpine and other habitats in addition to moist coniferous forests. The Pacific Northwest has been defined in various ways. For example, a typical encyclopaedia (Encyclopaedia Britannica 1983) limits it to Oregon, Washington and part of Idaho. The entomologist Melville Hatch, in a series of fascicles on “The beetles of the Pacific Northwest” (1953-1971) included British Columbia, Idaho, Oregon and Washington. Hitchcock eft a/. (1955-1969), in a treatment of the “Vascular plants of the Pacific Northwest”, published in the same series of the University of Washington as Hatch’s work, used detailed information for plants to circumscribe the area of Washington, Oregon, Northern Idaho, part of Montana, and southern British Columbia. Kavanaugh (1988) used the term for regions inland only to the western slopes of the Coast Ranges, Cascades and Sierra Nevada south to just south of San Francisco, and north to the Aleutian Islands, thereby including parts of Alaska, British Columbia, Washington, Oregon and California. Most insect distributions are not known in great detail and for most species only state- by-state or province-by-province records, and not more detailed distributions or habitat information, are readily available in published form. Therefore, the area treated here includes British Columbia (BC), Idaho (ID), Oregon (OR), and Washington (WA), although the diversity of British Columbia as well as of California (CA) also is analyzed separately in relation to the fauna of the region. These and other regions considered in this paper are shown in Figure 1, the caption for which gives the approximate land areas of the regions. INSECT DIVERSITY IN THE PACIFIC NORTHWEST North American Comparisons The occurrence of species of the selected groups in the Pacific Northwest (PNW) as a percentage of the North American fauna is shown in Table 1. Overall, some 29% of North American species have been recorded in the region, while the percentage in each state or province ranges from 16% (ID) to 20% (OR and BC). Nevertheless, there are considerable differences among groups. For example, the characteristic northwestern group Blephariceridae (48% of blepharicerid species occur in the PNW) is much better represented in OR and WA than elsewhere. The predominantly southwestern United States group Bethylidae (only 15% of species in PNW) is poorly represented throughout. J.ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 59 The group Culicidae (38% of species in PNW) is generally widely distributed in North America, and species are evenly distributed across the subregions. Northern syrphids are best represented in BC. Similar differences are visible among genera in the selected groups. Table 2 lists genera that contain more than 50 species. The fact that overall patterns for these 12 large genera — Figure 1. Regions of North America discussed in the text. The Pacific Northwest as considered here (approx. 1,583,000 km?) comprises Bntish Columbia (949,000), Idaho (213,000), Oregon (249,000), and Washington (172,000). The United States Pacific Northwest (ID-OR-WA, 635,000) is also compared with British Columbia, with California (405,000), with Illinois-Indiana—Ohio (343,000), which contains a similar number of reported species in the east, and with eastern North America. just over a quarter of the species— are virtually identical to those for the full dataset (compare the two bottom lines of Table 2) suggests that the patterns shown by these samples are representative. Subregions The number of species from the Pacific Northwest, and their occurrence in the different subregions, is shown in Table 3. Many species are shared among the subregions 60 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 (56-69%) but a substantial proportion of species have not been found in the whole of the region. About 13% of species have been found only in the region, with or without CA as explained below. Two small but distinctive fractions of species restricted to the area would be added if Alaska (for northern species such as some carabids, culicids and syrphids) and Nevada (for some southern elements such as some carabids, chrysidids and butterflies) were to be included in the “Pacific Northwest”. Clues to the different patterns of occurrence are suggested by the differences among families. The presence of groups of more southern or Californian affinity decreases from OR to BC, as in Curculionidae, whereas groups of more northern or Alaskan affinity increase, aS in Corixidae, and in Syrphidae, a family within which two better known but chiefly northern genera were analyzed. British Columbia British Columbia occupies a large area with a range of habitats including wet coastal forests in the south, dry interior grasslands, and relatively cold alpine and subalpine forests, especially in the north. Its fauna might therefore be expected to diverge from that of the United States Pacific Northwest, but in fact, partly because the northern fauna is relatively depauperate, nearly 80% of the species found there occur in ID, OR or WA too (Table 4). Seven percent of BC’s species have been found only in the PNW. From a Canadian perspective, many species occur in BC, and a significant fraction of all species (13% overall for the groups analyzed here) are confined to that province (Table 5), although there are considerable group-to-group differences. Additional reliable data are available for species distributions in Canada alone (Danks 1993, p. 60), and for these data 19% of 1583 species in 9 families (the whole of the Carabidae and 8 other different groups) have been reported only from BC; the percentage is increased especially because a full third of species of the characteristically western groups Scolytidae and Quediinae (Staphylinidae) are confined to the province (Danks 1993). One third of the species confined to BC (Table 5) nonetheless occur in the U.S. in ID, OR, or WA. Evidently many of these restricted Canadian species are part of the Pacific Northwestern fauna. California Habitats in northern California resemble those elsewhere in the PNW, although many different distinctive Californian and southwestern North American habitats occur in southern California. California as a whole therefore cannot be regarded as part of the Pacific Northwest, even though 7% of CA species otherwise occur only in the PNW (Table 6). Nevertheless, because some species centred in the PNW extend to CA, and because many more “southern” species characteristic of CA extend at least into OR, 56% of CA species occur also in the region considered here (Table 6). Species in common Within the region, many species are shared (Table 7). For example, 85% of Washington species have been collected also in Oregon; 75% of Oregon species are shared with Washington. About 65% of the United States Pacific Northwestern species occur also in CA, and 63% of them also in BC. However, only 30% of the same species occur in an area with a similar number of species farther east (see Fig. 1). Once again there are considerable differences from group to group (Table 7). For example, the number of species shared between WA and OR is especially high in groups such as the Lycaenidae. Although relatively few species of characteristically western groups (e.g. Blepharicerids) occur in eastern N. America, the relatively consistent J.LENTOMOL. SOc. BRIT. COLUMBIA 92, DECEMBER, 1995 61 occurrence in the east of PNW species in most groups is more striking. Indeed, nearly half of all the Pacific Northwest species are found to the east of a line from Manitoba to Texas (see Fig. 1; Table 7): many North American species are widely distributed and occur in different regions. Range types Several consistent types of ranges of species that occur in the Pacific Northwest can be detected. A detailed analysis is beyond the scope of this paper, but Kavanaugh (1988) recognized restricted coastal, coast centred, Great Basin, Rocky Mountain and transAmerican species (in addition to mainly northern range types), suggesting that since deglaciation species have entered the PNW by several common routes. In addition, prairie species enter the eastern part of the region not included by Kavanaugh. Widespread and even transcontinental species are very well represented (Table 7, final column). Many others are more-or-less broadly western. Some species, as already noted, are restricted to the Pacific Northwest. Those that are confined to the PNW and surrounding areas show a variety of patterns, among which characteristic types are northern (e.g. PNW to southeastern Alaska and the Yukon Territory) and southern coastal (e.g. PNW to CA); for sample patterns see Scott (1986), Kavanaugh (1988) and papers cited there, and also compare plant ranges, e.g. Preston (1961). The variety of the individual ranges suggests that current distributions have developed in many different and complex ways. Kavanaugh (1988) emphasized barriers to the dispersal of insect species in the region, noting that centres of endemism include central Idaho, the northern Cascades, and southern and northern coastal centres. CONCLUSIONS In the absence of full and detailed data on the ranges and habitats of large numbers of species, analysis of state and provincial records is helpful for characterizing regional diversity (Danks 1993, 1994a, b). This analysis for the Pacific Northwest — BC, ID, OR, WA — suggests that 29% of the species in North America, some 26,000 reported species, occur in the region (Table 2). Additional species revealed by further collecting, especially in old-growth forest canopies and in some montane habitats, would be expected to augment this number. Nearly half of the species from the Pacific Northwest are widely distributed in North America; indeed, 30% of them occur in Illinois, Indiana and Ohio alone (Table 7). On the other hand, 13% of all species (or a quarter of the western species) are confined to the Pacific Northwest, with or without occurrence in California, northern parts of which have habitats characteristic of the main part of the zone. Within the region, Oregon and the larger British Columbia have the most species, estimated to be about 18,000 each (Table 2). Almost half of the rich California fauna does not occur in the Pacific Northwest; however, the smaller fauna of BC is dominated by the nearly 80% of species that occur also in WA, OR, or ID. Despite these generalizations for the fauna as a whole, there are many differences among different groups (e.g. Tables 1, 2). Such differences suggest, for example, that groups with more species in and especially confined to the region, including Blephariceridae and some Carabidae and Curculionidae, would be especially useful for investigation of why these species contribute to the fauna to an unusual degree. The differences confirm too that current distributions depend on a wide variety of ecological and historical factors, reflecting the evolution and dispersal of species and the 62 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 modification and development of habitats, which have taken place in diverse ways over time. The variety of range types among the species that contribute to the fauna of the Pacific Northwest, and the combinations and intergradations of these range types, attest to the complexity of these processes. | Therefore, analysis of state and provincial records provides useful indexes of regional diversity, but fuller explanations about the nature and origin of the fauna require further systematic and ecological work. Kavanaugh (1979a, b, 1980, 1981, 1988) has been able to develop some explanations from prolonged and detailed studies of carabids of the genus Nebria, which contains many restricted northwestern species. Similar studies still are very limited for most of the groups treated here, even though they are among the best known taxonomically in North America. ACKNOWLEDGEMENTS This paper was prepared as the basis of a presentation at the 1995 Entomological Society of Canada / Entomological Society of British Columbia symposium on diversity in the Pacific Northwest. I thank Dr. Robb Bennett (BC Ministry of Forests) for stimulating my interest in the region by inviting me to contribute to the symposium, and Dr. David Kavanaugh (California Academy of Sciences) for helpful comments on the manuscript. I again acknowledge the information and advice provided by the many systematists cited in the acknowledgements of an earlier paper on North Amenican diversity (Danks 1994b). REFERENCES Atkinson, T. H., P. G. Koehler and R. S. Patterson. 1991. Catalog and atlas of the cockroaches (Dictyoptera) of North America north of Mexico. Misc. Pubs. Entomol. Soc. Am. 78: 1-86. Bohart, R. M. and L. S. Kimsey. 1982. A synopsis of the Chrysididae in America north of Mexico. Mem. Am. Entomol. Inst. 33: 1-266. Bousquet, Y. and A. Larochelle. 1993. Catalogue of the Geadephaga (Coleoptera: Trachypachidae, Rhysodidae, Carabidae including Cicindelini) of America north of Mexico. Mem. Entomol. Soc. Can. 167. 397 pp. Danks, H.V. 1993. Patterns of diversity in the Canadian insect fauna. pp. 51-74. In: Systematics and entomology: diversity, distribution, adaptation and application. Ball, G.E. and H.V. Danks (eds.). Mem. Entomol. Soc. Can. 165. 272 pp. Danks, H.V. 1994a. La diversité des espéces d’insectes du Québec, vues dans une perspective nord- américaine. Rev. Entomol. Québec 37: 46-51 [1992] Danks, H.V. 1994b. Regional diversity of insects in North America. Am. Entomol. 40: 50-55. Danks, H.V. in press. Terrestrial arthropods in the nearctic region: diversity and resources for study. In: Biodiversity and Taxonomy of Insects and Arachnids: A Global Perspective. K.C. Kim (ed.). Universal Book Services, Leiden. Darsie, Jr., R. F. and R. A. Ward. 1981. Identification and geographical distribution of the mosquitoes of North America, north of Mexico. Mosquito Syst. Suppl. 1: 1-313. Eidt, D. C. 1964. The life histories, distribution and immature forms of the North American sawflies of the genus Cephalcia (Hymenoptera: Pamphiliidae). Mem. Entomol. Soc. Can. 59: 1-56. Encyclopaedia Bnittanica. 1983. The New Encyclopaedia Brittanica, 15th edition, 30 vols. Encyclopaedia Brittanica, Chicago. : Evans, H. 1978. The Bethylidae of America North of Mexico. Mem. Am. Entomol. Inst. 27: 1-332. Froeschner, R. C. 1988a. Pentatomidae, pp. 544-597. In: Catalog of the Heteroptera, or True Bugs, of Canada and the Continental United States. Henry, T.J. and R.C Froeschner (eds.). Brill, Leiden. 958 PP. Froeschner, R. C. 1988b. Tingidae, pp. 708-773. In: Catalog of the Heteroptera, or True Bugs, of Canada and the Continental United States. Henry, T.J. and R.C. Froeschner (eds.). Brill, Leiden. 958 pp. J.ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 63 Hatch, M. 1953-1971. The beetles of the Pacific Northwest. Univ. Wash. Pubs. Biol. 16, 5 parts. Henry, T. J. and R. C. Froeschner. 1992. Corrections and additions to the "Catalog of the Heteroptera, or True Bugs, of Canada and the continental United States." Proc. Entomol. Soc. Wash. 94: 263-272. Hitchcock, C.L., A. Cronquist, M. Ownbey and J.W. Thompson. 1955-1969. Vascular plants of the Pacific Northwest. Univ. Wash. Pubs. Biol. 17, 5 parts. Hogue, C. L. 1987. Blephariceridae. Flies of the Nearctic Region. Vol. II, Part 4: 1-172. E. Schweizerbart'sche Verlagsbuchhandlung (Nagele u. Obermiller), Stuttgart. Hurley, R. L. 1985. Dolichopodidae: Hydrophorinae. Flies of the Nearctic Region. Vol. VI, Part 6, No. 1: 1-112. E. Schweizerbart'sche Verlagsbuchhandlung (Nagele u. Obermiller), Stuttgart. Kavanaugh, D.H. 1979a. Rates of taxonomically significant differentiation in relation to geographical isolation and habitat: examples from a study of the Nearctic Nebria fauna. pp. 35-57. In: Carabid Beetles: Their Evolution, Natural History, and Classification. Erwin, T.L., G.E. Ball, D.R. Whitehead and A.L. Halpern (eds.). Proceedings of the First International Symposium of Carabidology, Smithsonian Institution, Washington, DC, August 21, 23, and 25, 1976. Junk, The Hague. 635 pp. Kavanaugh, D.H. 1979b. Investigations on present climatic refugia in North America through studies on the distributions of carabid beetles: concepts, methodology and prospectus. pp. 369-381. In: Carabid Beetles: Their Evolution, Natural History, and Classification. Erwin, T.L., G.E. Ball, D.R. Whitehead and A.L. Halpern (eds.). Proceedings of the First International Symposium of Carabidology, Smithsonian Institution, Washington, DC, August 21, 23, and 25, 1976. Junk, The Hague. 635 pp. Kavanaugh, D.H. 1980. Insects of western Canada, with special reference to certain Carabidae (Coleoptera): present distribution patterns and their ongins. Can. Entomol. 112: 1129-1144. Kavanaugh, D.H. 1981. Studies on the Nebnini (Coleoptera: Carabidae), IV. Four new Nebria taxa from western North America. Proc. Calif. Acad. Sci. 42: 435-442. Kavanaugh, D.H. 1988. The insect fauna of the Pacific Northwest coast of North America: present patterns and affinities and their origins. pp. 125-149. In: Origins of the North American Insect Fauna. Downes, J.A. and D.H. Kavanaugh (eds.). Mem. Entomol. Soc. Can. 144. 168 pp. Knutson, L. V. 1973. Taxonomic revision of the aphid-killing flies of the genus Sphaerophoria in the western hemisphere (Syrphidae). Misc. Pubs. Entomol. Soc. Am. 9: 1-50. Middlekauff W. W. 1958. The North American sawflies of the genera Acantholyda, Cephalcia, and Neurotoma (Hymenoptera, Pamphilidae). Univ. Calif. Pubs. Entomol. 14: 51-173. Middlekauff W. W. 1964. The North American sawflies of the genus Pamphilius (Hymenoptera: Pamphiltidae). Univ. Calif. Pubs. Entomol. 38: 1-80. O'Bnen, C. W. and G. J. Wibner. 1982. Annotated checklist of the weevils (Curculionidae sensu lato) of North America, Central America, and the West Indies (Coleoptera: Curculionoidea). Mem. Am. Entomol. Inst. 34: 1-382. Olmi, M. 1984. A revision of the Dryinidae (Hymenoptera). Mem. Am. Entomol. Inst. 37 (2 parts): 1-1913. Olmi, M. 1989. Supplement to the revision of the World Dryinidae (Hymenoptera: Chrysidoidea). Frustula Entomol. n.s. 12: 109-395. Polhemus, J. T., R. C. Froeschner and D. A. Polhemus. 1988. Corixidae. pp. 93-118. In: Catalog of the Heteroptera, or True Bugs, of Canada and the Continental United States. Henry, T.J. and R.C. Froeschner (eds.). Brill, Leiden. 958 pp. Preston, R.J., Jr. 1961. North American Trees. 2nd edition. Iowa State University, Ames, Iowa. 395 pp. Scott, J. A. 1986. The Butterflies of North America. A Natural History and Field Guide. Stanford University Press, Stanford, CA. 583 pp. Shinohara, A. and D. R. Smith. 1983. Pamplilius middlekauffi Shinohara and Smith, new species, for "Pamphilius ocreatus" of authors (Hymenoptera: Pamphiliidae). Proc. Entomol. Soc. Wash. 85: 858- 859. Vockeroth, J. R. 1990. Revision of the nearctic species of Platycheirus (Diptera: Syrphidae). Can. Entomol. 122: 659-766. 64 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Table 1 Occurrence of North American species in selected groups in the Pacific Northwest “% of these spp. recorded in Order/Family No. of N. BC ID OR WA _ BC, QD, American spp. OR, WA Dictyoptera 69 6 6 9 | 9 Hemiptera: Corixidae 125 26 9 16 21 36 Pentatomidae 221 18 13 13 10 23 Tingidae 153 14 7) 12 9 23 Coleoptera: Carabidae (part) (e4 19 12 16 16 26 Curculionidae(part) 483 7 9 15 11 18 Diptera: Blephariceridae 25 16 20 44 36 48 Culicidae 162 27 29 29 om | 38 Dolichopodidae (part) 49 35 24 29 27 47 Syrphidae (part) 83 67 36 45 43 73 Lepidoptera: Papilionidae/ Pieridae 78 38 a2 36 32 44 Nymphalidae 165 39 pie 28 29 47 Lycaenidae 124 29 35 35 34 43 Hesperiidae 221 11 13 14 i 18 Hymenoptera: Pamphiliidae 71 pee 17 3 30 Chrysididae 230 20 34 42 25 44 Bethylidae 197 7 10 12 9 15 Dryinidae 109 15 6 6 5 17 TOTAL 3322 20 16 20 17 29 Data for this and subsequent tables derived from Atkinson ef a/. 1991 (Dictyoptera_ s.s. {cockroaches]), Polhemus ef al/., 1988, Henry and Froeschner 1992 (Corixidae), Froeschner 1988a (Pentatomidae), Froeschner 1988b (Tingidae), Bousquet and Larochelle 1993 (Carabidae), O’Brien and Wibner 1982 (Curculionidae), Darsie and Ward 1981 (Culicidae), Hogue 1987 (Blephariceridae), Hurley 1985 (Dolichopodidae), Vockeroth 1990, Knutson 1973 (Syrphidae), Scott 1986 (Papilionidae, Pieridae, Nymphalidae, Lycaenidae, Hesperiidae), Middlekauf 1958, 1964, Shinohara and Smith 1983, Eidt 1964 (Pamphiliidae), Bohart and Kimsey 1982 (Chrysididae), Evans 1978 (Bethylidae), Olmi 1984, 1989 (Dryinidae) J.LENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 65 Table 2 Occurrence of North American species in selected larger genera in the Pacific Northwest % of these spp. recorded in Family / Genus No. of N. BC ID OR WA _ BC, ID, American spp. OR, WA Carabidae: Agonum gh 44 15 18 ° 30 45 Cicindela 90 8 8 11 8 16 Chlaenius 51 12 4 8 12 12 Nebria 54 26 15 24 30 48 Curculionidae: Apion 154 5 8 12 12 14 Listronotus 76 13 16 20 11 22 Anthonomus 102 12 11 25 16 29 Conotrachelus 60 2 0 0 2 2 Sphenophorus 64 8 14 16 16 20 Culicidae: Aedes 76 4] 39 38 37 5)! | Syrphidae: Platycheirus 70 63 33 cy) 39 69 Chrysididae: Chrysis 79 24 47 48 35 58 TOTAL (These genera) 947 20 17 21 20 31 TOTAL (All genera) 3322 20 16 20 17 29 66 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Table 3 Occurrence of Pacific Northwest species in selected groups from British Columbia, Idaho, Oregon and Washington % of these spp. recorded in % recorded only from BC, ID, No. of spp. OR, WA, in BC, ID, with or OR, WA BC ID OR WA without CA Dictyoptera 6 67 67 100 83 0 Hemiptera: Corixidae 45 73 24 44 58 18 Pentatomidae 51 76 oy! 55 45 6 Tingidae $5 63 29 51 40 1] Coleoptera: Carabidae (part) 198 74 44 60 63 27 Curculionidae (part) 86 42 51 83 64 O77 Diptera: Blephariceridae 12 33 42 92 75 42 Culicidae 62 71 76 76 69 5 Dolichopodidae 23 74 52 61 57 17 (part) Syrphidae (part) 61 92 49 61 59 8 Lepidoptera: Papilionidae/ 34 88 74 82 74 6 Pieridae Nymphalidae 78 83 58 60 62 4 Lycaenidae 53 68 83 83 79 2 Hesperiidae 39 64 12 a7 67 10 Hymenoptera: Pamphiliidae 21 90 24 57 43 5 Chrysididae 101 47 78 95 a7 2 Bethylidae 30 47 67 TT 60 0 Dryinidae 19 84 Bd 37 26 1] TOTAL 954 68 56 69 61 13 J.ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 67 Table 4 Occurrence of species from British Columbia in selected groups in relation to occurrence in Idaho, Oregon and Washington % of BC spp. % of BC spp. otherwise only No. of spp. recorded also in ID, OR, recorded from in ID, OR, WA, with or Order/Family BC WA without CA Dictyoptera 4 100 0 Hemiptera: Corixidae 33 58 9 Pentatomidae 39 82 5 Tingidae 22 50 5 Coleoptera: Carabidae (part) 147 77 16 Curculionidae (part) 36 2 1d Diptera: Blephariceridae 4 100 0 Culicidae 44 89 2 Dolichopodidae (part) 17 76 12 Syrphidae (part) 56 75 36 Lepidoptera: Papilionidae/ Pieridae 30 83 33 Nymphalidae 65 69 2 Lycaenidae 36 94 3 Hesperiidae 25 96 0 Hymenoptera: Pamphiliidae 19 53 0 Chrysididae 47 96 0 Bethylidae 14 79 i Dryinidae 16 56 0 TOTAL 654 78 1 68 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Table 5 Occurrence of species, confined in Canada to British Columbia, in Idaho, Oregon and Washington % of spp. confined in % of Canadian Canada to BC No. of %ofN.Am. spp. confined that occur in Order/Family Canadian spp. spp. in Canada toBC. ID,OR, WA Dictyoptera 7 10 0 -- Hemiptera: Corixidae 69 55 10 43 Pentatomidae 63 29 17 18 Tingidae 35 23 34 i Coleoptera: Carabidae (part) 286 38 14 67 Curculionidae (part) 105 22 15 25 Diptera: Blephariceridae q 28 0 -- Culicidae 74 46 fy) 40 Dolichopodidae (part) 39 80 15 33 Syrphidae (part) 73 88 |i) 36 Lepidoptera: Papilionidae/ Pieridae 46 59 13 17 Nymphalidae 89 54 9 25 Lycaenidae 55 44 13 14 Hesperiidae 55 25 9 0 Hymenoptera: Pamphiliidae 45 63 18 0 Chrysididae 61 oe 23 0 Bethylidae 23 13 4 100 Dryinidae 38 35 3 100 TOTAL 1172 35 13 33 J.ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 69 Table 6 Occurrence of species from California in selected groups in relation to occurrence in Idaho, Oregon, and Washington % of CA spp. % of CA spp. otherwise only No. of spp. recorded also in ID, OR, recorded from inID, OR, WA, with or Order/Family CA WA . without BC Dictyoptera 14 29 0 Hemiptera: Corixidae 24 67 17 Pentatomidae 68 51 4 Tingidae 32 40 3 Coleoptera: Carabidae (part) 185 44 13 Curculionidae (part) 94 63 14 Diptera: Blephariceridae 16 te 31 Culicidae 48 ad 2 Dolichopodidae (part) w 83 25 Syrphidae (part) 27 85 d Lepidoptera: Papilionidae/ Pieridae 36 69 6 Nymphalidae 59 73 4 Lycaenidae 64 75 2 Hesperiidae 60 a2 7 Hymenoptera: Pamphiltidae 18 2, 6 Chrysididae 164 af ] Bethylidae 79 33 0 Dryinidae 23 35 0 TOTAL 1023 56 7 70 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Table 7 Occurrence of species in selected groups from the Pacific Northwest in adjacent and in distant regions % spp. % spp. % spp % spp. from ID- from ID- % spp. % spp. from ID- from ID- OR-WA OR-WA from WA from OR OR-WA OR-WA also in IL- also east of Order/Family also in OR alsoinWA alsoinCA alsoinBC IN-OH MB to TX Dictyoptera 100 83 67 67 . 83 83 Hemiptera: Corixidae 62 80 a2 61 26 32 Pentatomidae 70 57 80 qs 4] 50 Tingidae 71 56 54 46 33 42 Coleoptera: Carabidae (part) qb) 80 50 69 28 37 Curculionidae (part) 87 68 qi 4] 33 44 Diptera: Blephariceridae 89 73 100 33 0 0 Culicidae 91 83 65 68 44 65 Dolichopodidae 100 93 53 68 1] 42 (part) Syrphidae (part) 86 84 49 89 26 62 Lepidoptera: Papilionidae/ 96 86 86 86 28 59 Pieridae Nymphalidae 88 89 aS 79 32 47 Lycaenidae 95 91 94 67 31 45 Hesperiidae 85 73 82 63 30, 45 Hymenoptera: Pamphiliidae 100 (2) 100 a 0 31 Chrysididae 95 57 95 46 26 4] Bethylidae 89 70 93 39 43 64 Dryinidae 40 29 67 1s 25 92 TOTAL 85 75 65 63 30 47 J.LENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Table 8 Summary of the diversity of species in the regions discussed % of spp. reported in Estimated total no. Region selected groups of spp. reported North America (100) 90,250 Canada ti) 31,590 Pacific Northwest (BC, ID, OR, WA) 29 26,170 U.S. Pacific Northwest (ID, OR, WA) 24 ; 21,660 British Columbia (BC) 20 18,050 Oregon (OR) 20 18,050 Washington (WA) 17 15,340 Idaho (ID) 16 14,440 California (CA) 31 27,980 Middle states (IL, IN, OH) 26 23,460 *y ne aif uA ns es neh * J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 73 Feeding and performance of Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae), reared on nightshade and potato GUOMIN XU and GARRELL E. LONG DEPARTMENT OF ENTOMOLOGY WASHINGTON STATE UNIVERSITY PULLMAN, WA 99164-6382 ABSTRACT Larval feeding rates, growth rates of immatures, and adult fecundities were measured for Colorado potato beetle fed hairy nightshade (Solanum sarrachoides) or potato (Solanum tuberosum). Hairy nightshade is an important economic weed in local agriculture. The larvae consumed more dry weight of potato foliage than nightshade. Developmental rate was higher for larvae fed potato than for those fed nightshade. Mortality was similar on the two hosts. Pupae and adults obtained from larvae reared on nightshade were significantly heavier than those from larvae reared on potato. There were no significant effects of the rearing host on adult female longevity. Fecundity, however, was higher for beetles fed on nightshade than those fed on potatoes. We conclude that hairy nightshade is an important alternative and acceptable host plant for the Colorado potato beetle. Key words: Hairy nightshade, potato, development, foliage consumption, survival, adult longevity, fecundity INTRODUCTION Colorado potato beetle, Leptinotarsa decemlineata (Say) has adapted to different local host plants, depending upon geographic location (Harrison 1987, Hsiao 1985). Hairy nightshade, Solanum sarrachoides Sendt., for example, serves as an alternative host of the pest in Colorado (Horton & Capinera 1990), Utah (Hsiao, personal communication) and Washington (Brown ef a/. 1980). This weed species, a native of South America, is locally abundant in potato (Solanum tuberosum L.) growing regions in the Pacific Northwest (Callihan et al. 1990). In late season, large numbers of beetles were seen feeding and ovipositing on nightshade plants, to the extent that beetle densities were much higher on nightshade than on potato ( Xu & Long, unpublished data). Feeding and performance of the beetle has not been well documented with the beetle population in Washington. This study had two objectives: first, to measure foliage consumption and survival of larval stages, and longevity and fecundity of the adult beetle fed either nightshade or potato foliage; second, to determine whether the beetle was preferably adapted to the source host (host species from which the egg mass was collected) (Horton & Capinera 1990). MATERIALS AND METHODS Egg masses from first generation beetles were collected from nightshade and potato plants on 9 July, 1993 at the USDA Field Station, 8 miles east of Moxee, Washington. Eggs were brought to the laboratory and kept in an incubator until they had hatched (27 + 1 °C, 16L:8D photoperiod) 74 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Potatoes, (var. Russet Burbank) were planted in 3-litre plastic flower pots using standard potting soil (Sun Gro Horticulture Inc., Puyallup, WA). Hairy nightshade, S. sarrachoides, was germinated from seed and transplanted into pots as seedlings, using the same brand of potting soil. Plants were grown in the laboratory under a pressurized sodium vapor grow light. Both host species were regularly watered and were fertilized weekly with "Schultz-Instant" Liquid Plant Food (Schultz Co.). Five newly-hatched larvae were randomly selected from each egg mass. Larvae were individually transferred to a small plastic petri dishes (5.5 cm x 1.5 cm), with one larva per dish. Each dish contained one to four leaf disks (2 cm diameter) from the same host species from which the egg mass had been obtained. The number of leaf disks that were provided depended upon larva size. A piece of wet cotton roll was placed in each dish to maintain humidity. Dishes and larvae were placed in an incubator at a constant temperature of 27+1°C and photoperiod of 16L:8D. Observations of the larval development and survival were at 24 hr intervals. Larval instars were determined by the presence of exuvium. A total of 105 larvae from each host plant were used. Foliage consumption by each instar was estimated using a leaf disk technique we developed. Disks were cut from leaves using a cork-borer of 2 cm diameter. One to four disks per dish were provided, and replaced daily. For measuring the leaf area consumed, several circles of the same diameter as the disks were drawn on grid paper (2.5 mm). Disks which had been fed on by larvae were placed on the circles, and the consumed areas were estimated by counting exposed square units. The number of square units were then converted to square centimeters. We found the leaf disk technique to be reliable. No significant differences in development or weight of pupae and adults were found between disk and whole plant studies, as long as enough leaf disks were provided for the beetles (Xu & Long, unpublished data). Since potato leaves are visually thicker than nightshade leaves, there might be differences in foliage weight between the two hosts with the same leaf areas. The difference was determined by measuring the dry weights of randomly selected leaf disks of both hosts. The disks were dried in an oven at 55 °C for 48 hours before dry weights were recorded. Different quantities of foliage were also clipped from both hosts. Leaf area of the foliage was measured. Dry weight was also determined as noted above. The relationship between leaf area and dry weight was estimated using linear regression, in which dry weight (mg) was the dependent variable and leaf area (cm?) was the independent variable. Foliage consumption was then expressed in terms of both leaf area and dry weight. When the mature larvae stopped feeding (prepupae) they were transferred to individual rearing cups (38 ml) containing soil collected from a potato field. The cups were kept in the same incubators as those used for larval development, and were monitored daily for pupation of beetles. The pupae were checked daily until the emergence of adults. Newly emerged adults were sexed. Three to five beetles of each sex from the two host species were then randomly selected and transferred to a cage (30x30x60 cm*) to monitor adult longevity and fecundity. A pot of nightshade or potato with young shoots was provided. Five cages were used for each host. A total of 25 females was used for the nightshade test, and 19 females for the potato test. The cages were kept at room temperature (21+1°C)with a photoperiod of 16:8 (L:D).-Foliage was replaced every other day. Egg masses on plants were counted and removed daily; and the number of eggs per egg mass was also recorded. The production of eggs was calculated daily using total number of eggs on a plant divided by the number of females in that cage. Survival of adults was recorded every day until the beetles died. J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 ie) As described above, all beetles in earlier studies were fed only the source host, that is, the host species from which the egg mass was obtained. But we also determined whether beetles were most adapted to their source host, using cross-host plant tests (Horton & Capinera 1990). Forty larvae newly hatched from eggs obtained on nightshade plants were randomly selected. Twenty of the forty larvae were provided with leaf disks of nightshade, and the other 20 with leaf disks of potato. Another 40 larvae hatched from eggs collected on potato plants were also used, with half of them fed nightshade and the other half fed potato. The larvae were maintained in the manner as described above. Development and survival were monitored daily until adult emergence. Pupae were sexed using the characters described by Pelletier (1993), and the weight of each pupa was recorded. Newly emerged adults were also sexed and weighed. Data for larval feeding, adult longevity and fecundity were compared between host species using f - tests. Data for larval and pupal survival on the two hosts were analyzed using chi - square test. A two - way factorial (source host x feeding host) analysis of variance (ANOVA with completely randomized design) was done for data obtained from the cross - host experiments, testing for effects of source host (host from which eggs were obtained), feeding host (host for larval feeding) and their interaction. Student-Newman- Keuls tests were conducted where appropriate. (SAS Institute 1988, 1990). RESULTS Larval Feeding. Most foliage consumption took place in the late larval stages (Table 1). For both hosts, about 70% of the leaf area was consumed by the fourth instars, about 20% by the third instars and less than 10% by the first and second instars. A t¢ - test indicated a significant difference between the two hosts in foliage consumption (cm’) for the entire larval period, (p = 0.0017). Larvae consumed more potato than nightshade foliage for completion of their development. However, the ¢ - test failed to show significant differences between the two hosts in larval feeding for the first, second and fourth instars. The difference was significant for the third instar, which may have contributed to the significant difference in total larval feeding (Table 1). Table 1. Average foliage consumption (per stage) by larval Colorado potato beetles! Leaf area [cm*(SE)] Dry weight [mg(SE)] Larval stage Nightshade Potato Nightshade Potato ]* instar 0.48(0.02)a 0.51(0.02)a 0.79(0.03)a_ 1.66(0.08)b 2"? instar 1.49(0.09)a_ = 1.69(0.11)a 2.43(0.15)a = 5.51(0.36)b 3 instar 5.17(0.22)a 6.39(0.25)b 8.42(0.36)a 20.82(0.83)b 4" instar 19.05(0.38)a 19.30(0.41)a 31.07(0.63)a 62.95(1.33)b Entire larval stage 26.19(0.35)a 27.88(0.40)b 42.71(0.56)a 90.94(1.30)b ' 85 individuals developed on nightshade foliage and 90 on potato foliage. Means followed by different letters within the same row are significantly different, f - test (p < 0.05). 76 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 Leaf disks of potato were thicker than those of hairy nightshade, and consequently, dry weight differed between the two hosts. On average, dried potato leaf disks weighed 10.22 mg (SE = 0.18, n = 20); dried nightshade leaf disks weighed 5.23 (SE = 0.12, n = 20). A linear regression model was fitted to the relationship of dry weight (Y) to leaf area (X): For nightshade foliage: Y = 1.089 + 1.602 * X (R* = 0.997, n= 22): For potato foliage: Y = - 0.321 + 3.277 * X (R? = 0.999, n = 20). Leaf area consumption was then transformed to dry weight using these models. As indicated by ¢ - test, on a dry weight basis, beetles consumed significantly more potato than nightshade foliage (Table 1). Survival. Larval survival of the beetle was similar on the two hosts (p > 0.05). Little difference in pupal survival was found between the two hosts (p > 0.05, Table 2). Sixty- nine adults emerged from 105 individuals fed on potato foliage, and sixty-five from same number of individuals fed on nightshade foliage. Table 2. Survival (%+SE) of total larval and pupal Colorado potato beetles Developmental stage Nightshade Potato p - value lst instar 93.3342.44 99.05+0.95 0.9739 2nd instar 93.8842.42 98.05+1.36 0.9810 3rd instar 95.6522 12 95.10+2.14 0.9975 4th instar 86.36+3.66 $3.5143.77 0.9862 pupa 85.53+4.04 85.19+3.95 0.9984 Adult longevity. Adult beetles survived for about two months, although there was a large variation among individuals. On nightshade foliage, the range of longevity varied from 9 to 65 days for females, and 24 to 61 days for males. On potato foliage, the range was 13 - 57 days for females, and 12 - 57 days for males. As shown in Table 3, the average longevity of females was similar for the two hosts (p = 0.8198); the average longevity of males was significantly different between the two hosts (p = 0.0138). Table 3. Adult longevity in days’ Nightshade Potato N Mean+SE N Mean+SE Female 25 37.76+2.80a 19 38.82+3.84a Male 23 41.35+2.20a 17 31.94+3.02b ' Means followed by different letters in the same row are significantly different, f -test (p < 0.05). J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 77 Fecundity. Egg mass per female ranged from 4 - 43 on nightshade foliage, and 7 - 32 on potato foliage. Females that developed on nightshade showed higher fecundity than those on potatoes; those fed on nightshade foliage laid about 6 more egg masses per female than those fed on potato foliage (p = 0.0401). The number of eggs per female was thus higher for beetles on nightshade than those on potato (p = 0.0221). A f¢ - test failed to show a significant difference in number of eggs per egg mass between females fed on the different host plants (p = 0.3041) (Table 4). Table 4. Fecundity of Colorado Potato Beetles’ Nightshade Potato N Mean+SE N Mean+SE Egg masses/female 25 25.44+2 67a 19 18.15+3.06b Eggs/female 25 495.36+53.60a 19 395.42+61.69b Eggs/egg mass 636 19.39+0.72a 345 =. 20.51+0.70a ' Means followed by different letters in the same row are significantly different, f -test (p < 0.05). Cross - host test. Larval development time (days) was not affected by source host (p = 0.1652), whereas the effect of feeding host was highly significant (p = 0.0001). The interaction between source host and feeding host was not significant (p = 0.0805), indicating that the effect of feeding host on larval development was independent of source host. Larvae that fed on potato foliage developed faster than those fed on nightshade foliage (Table 5). Table 5. Effects of source host and feeding host on larval development time (daystSE), pupal weight and adult weight (mg+SE) of Colorado potato beetles’ Source Host Nightshade Potato Feeding Host Nightshade Potato Nightshade Potato Development time (58)° 15.49+0.19a 14.2640.26b 15.94+1.67a 13.87+0.22b Female pupa (33) 176.2842.95a 121.6543.98b 162.7642.60a 126.20+3.66b Male pupa (31) 143.90+3.75a 104.75+1.75b 142.8844.44a 118.66+2.88b Female adult (29) 138.0643.41a 93.57+8.84b 138.15+4.13a 107.13+3.96b Male adult (28) 121.3041.73a 85.6643.09b 117.484+3.77a 101.04+43.17ab ' Means followed by different letters within the same row are significantly different, Student-Newman-Keuls test (p < 0.01). * Degree of freedom from ANOVA. The effects of feeding host on pupal and adult weight were also highly significant (p = 0.0001 for pupal female and male, p = 0.0006 for adult male and p = 0.0005 for adult female, respectively). Pupae and adults from larvae that were fed nightshade foliage were significantly heavier than those from larvae fed potato foliage. Pupal females were 78 J. ENTOMOL. SOC. BRIT. COLUMBIA 92, DECEMBER, 1995 heavier than males, so were adult females than males. Adults were lighter than pupae (Table 5). ANOVA failed to demonstrate significant source host effects or a significant interaction of source host with feeding host (p > 0.05). Percent survival of larvae was similar for both source hosts and for both feeding hosts. For nightshade as source host, survival of post-hatching immatures (first instar through pupa) was 70% when nightshade foliage was provided as a feeding host, and 80% when potato foliage as a feeding host. Similarly, for potato as source host, survival was 80% on nightshade foliage, and 65% on potato foliage. DISCUSSION Hairy nightshade is an important host plant of the Colorado potato beetle in Washington and other areas (Horton & Capinera 1990). This weed is locally abundant in potato growing regions in the Pacific northwest (Callihan et a/. 1990), and serves as an alternative food source for the beetle (Brown ef a/. 1980). Adults readily deposited eggs on hairy nightshade (Table 4). The performance of Colorado potato beetles on the two feeding hosts was independent of source host, indicating that the beetle is not adapted to a particular source host. Movements of beetles between the two hosts were found in Washington, so the lack of specificity on the source host is not surprising. The first summer generation of the beetle develops primarily on potato, because the weed seeds generally do not germinate until after growth of the potatoes. However, adults of this generation readily move off potato to nightshade for oviposition (Xu & Long, unpublished data). Thus, a given female may- deposit eggs on both host species. Population densities of the second summer generation were much higher on this weed species than on potato (Xu & Long, unpublished data). We conclude that populations of the beetle have adapted to the potato-nightshade plant system in the Pacific Northwest, especially in Washington. Developmental rates of the beetle depend upon the host species (Brown ef al. 1980, Melville 1985), but variation occurs between geographic populations. We found that larvae fed on nightshade foliage developed more slowly than those fed on potato foliage (Table 5). In Colorado, however, larval growth rates were significantly faster on hairy nightshade than on potato, both early and late in the season (Horton ef al. 1988, Horton & Capinera 1990). Survival of the beetle differs among different host plants (Hare & Kennedy 1986). Wild species are less acceptable host plants for the Colorado potato beetle (Melville 1985, Neal ef al. 1991). We found that there were no significant differences in larval or pupal mortality between the two hosts (Table 2). Fecundity of the beetles is also affected by different host plants (Brown ef al.