increase in future years. Potato leafhopper averaged 32% 

 more abundant in the test blocks, but we still have no solid 

 evidence that this insect is truly injurious to bearing trees. 

 Leafmincrs were 27% more abundant in the test blocks, 

 but we fully expect leafminer parasites to increase to 

 substantial levels during summer months in future years. 



Second-stage IPM research for 1988 will concen- 

 trate on repeating the experimental designs for border row 

 sprays and apple maggot traps placed in perimeter apple 

 trees. The design which called for apple maggot traps in the 

 woods around an orchard will be eliminated. 



In conclusion, results of the first year of implem- 

 entation of several second-stage IPM practices in commer- 

 cial orchards give us cause to be optimistic about the future 

 of these practices in preventing injury to apple fruit during 

 June, July, and August and in fostering buildup of impor- 

 tant natural enemies of foliar pests. In succeeding years, we 

 will work on refining our second-stage techniques (includ- 



ing possible substitution of sticky spheres with insecticide- 

 impregnated non-sticky spheres), with the aim of being 

 able to recommend with confidence a truly integrated 

 behavioral, cultural, and biological approach to orchard 

 pest management. 



Acknowledpements . We thank the Massachu- 

 setts Society for Promoting Agriculture and the Northeast 

 Regional Project on Integrated Management of Apple 

 Pests (NE-156) for supporting our work on second-stage 

 apple IPM. Special thanks go to Leslie White and Esther 

 Ruiz who worked on the 1987 studies. Bill Coli, Kathleen 

 Leahy, Sue Butkcwich, and Dave Stanley also participated 

 in this program. 



Literature Cited 



1. Butkewich.S.L.andR.J.Prokopy. 1985. Update on 

 the relative toxicity of orchard pesticides to the predator 

 mite, Amblyseius fallacis. Fntit Notes 50(3): 9-11). 



*^f ^fi *il^ *it* 



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SINGING IN THE RAIN: THE EFFECT OF WEATHER ON 

 PLUM CURCULIO SPRING MIGRATION 



Susan L. Butkewich and Ronald J. Prokopy 

 Department of Entomology, University of Massachusetts 



The plum curculio (PC), Conotrachelus nenuphar 

 (Hebst), is a serious pest of stone and pome fruits east of 

 the Rocky Mountains. It is also one of the two most 

 important species attacking apples in the Northeast. Less 

 is known about the plum curculio than about any other key 

 apple pest. Several factors have been responsible for 

 Hmiting our success in understanding this insect. PCs are 

 cryptically colored and feign death when disturbed, making 

 behavioral studies difficult. In their northern range, PCs 

 overwinter in leaf litter outside the orchard and return to 

 host trees in the spring. The behavioral adaptations 

 involved in leaving the orchard in the fall, returning in the 

 spring, and locating a host, are complex and not well 

 understood. 



From a control standpoint, detection of PC move- 

 ment into an orchard in the spring is critical since PCs can 

 crawl quickly throughout a host tree, causing significant 

 damage to fruit in a short time. To illustrate the rapidity 



with which PC injury may appear, in 1987 unlrcatcd trees 

 in Conway, MA had 9% fruit injury on May 21 and 96% on 

 May 24! PC populations are difficult to monitor since they 

 usually are clumped rather than distributed. Presently, 

 control practices are initiated when feeding and cggiaying 

 scars on fruit reach economic threshold levels; however, by 

 the time fruit damage is detected, considerable fruit injury 

 already may have occurred throughout an orchard. More 

 effective techniques for monitoring PC appearance on host 

 plants in the spring would help us to overcome a major 

 stumblingblock in pest control within apple integrated pest 

 management programs in the Northeast. 



Many researchers have felt that PC spring migra- 

 tion is infiuenced by environmental factors. Quaintance 

 and Jenne (3) developed the mean temperature "rule" as 

 an index of PC activity, where a mean temperature above 

 60°F for 3 or 4 days will result in large migrations. Snap(5) 

 agreed with these conclusions. Whitcomb (6) found that 



11 



