volatiles: benzaldehyde, decanal, E-2-hexenal, ethyl 

 isovalerate, hexyl acetate, or limonene, each contained in 

 polyethylene vials. As reported in the summer 1999 issue of 

 Fruit Notes, each of these fruit volatiles has been found to 

 be attractive to PCs when evaluated in association with boll 

 weevil traps placed on the ground beneath host trees. We 

 also evaluated pheromone alone and an unbaited (control) 

 treatment. Dependmg on the volatile type, a different num- 

 ber of vials (2-5) was needed to achieve a release rate of 10 

 mg per day. For panel traps, vials containing fruit volatiles 

 were attached to the lower edge of the Plexiglas panels, and 

 one pheromone dispenser was attached to the upper edge. 

 For pyramid traps, vials containing volatiles and one phero- 

 mone dispenser were placed inside each boll weevil trap top 

 capping a pyramid trap. Vials containing benzaldehyde and 

 limonene, as well as grandisoic acid dispensers, were re- 

 placed on May 24 (beginning of fiaiit set), because endur- 

 ance of these compounds under the weather conditions of 

 this study was shorter than that estimated in the laboratory. 

 On April 30 (tight cluster stage of bud development), 

 40 clear Plexiglas panels and 40 pyramid traps were posi- 

 tioned in close proximity to woods (overwintering sites ad- 

 jacent to apple trees) and remained there until June 7 (end 

 of fruit-set stage). Traps were arranged in five groups of 16 

 traps each (dictated by the combination of eight odor treat- 

 ments and two trap types) and were deployed in pairs, with 

 one trap of each type (bearing the same odor treatment) 

 placed 1 m apart. Each pair was separated by 1 yards. Traps 

 were inspected every morning (at 7:30 AM) throughout the 

 study. 



Results 



Based primarily on phenological stage of apple bud and 

 fruit development, PC immigration was divided into early-, 

 mid- and late-season periods (tight cluster to bloom, petal 

 fall, and fruit set, respectively). Overall, 387 PCs were cap- 

 tured by traps during the 39-day study period. First PC cap- 

 tures by traps (3 PCs) occurred on May 2. Peak of adult 

 immigration was observed on May 5 (93 PCs, correspond- 

 ing to 24% of the season-long total, were captured by traps 

 on this particular day). Periodic peaks of adult captures by 

 traps seemed to coincide with rises in temperature (Figure 

 2), a factor that has been shown to influence both the emer- 

 gence of adults after overwintering and the appearance of 

 adults in host trees. 



During early-season (April 30-May 9), 266 adults (69% 

 of total) were captured by traps. Over this period, panel traps 

 baited with benzaldehyde plus pheromone or ethyl 

 isovalerate plus pheromone were about four-fold and three- 

 fold, respectively, more attractive to PCs than were unbaited 

 panel traps, and pyramid traps baited with benzaldehyde plus 

 pheromone or pheromone alone were about six-fold and 



three-fold, respectively, more attractive than were unbaited 

 pyramid traps (Figure 3a). 



During mid-season (May 10-24), only 36 PCs (9% of 

 total) were captured by traps, and there was little response 

 of PCs to traps of any type (Figure 3b), possibly on account 

 of prevailing cool weather unfavorable for adult activity. 



During late-season (May 25-June 7), 85 PCs (22% of 

 total) were caught by traps. We found that just after replac- 

 ing vials containing benzaldehyde and pheromone dispens- 

 ers, panel and pyramid traps baited with benzaldehyde plus 

 pheromone were again much more attractive (six-fold and 

 eleven-fold, respectively) to PCs than any other traps (baited 

 or unbaited) of either type (Figure 3c). 



Conclusions 



This study represents a step toward development of a 

 more efficient monitoring tool for PC. By placing panel and 

 pyramid traps baited with benzaldehyde in combination with 

 pheromone in close proximity to woods, we were able to 

 determine the first arrivals of PCs in the orchard (during 

 tight cluster), as well as the peak (during full bloom) and 

 possible end (during fruit set) of PC immigration. Benzal- 

 dehyde plus pheromone proved to be the most attractive lure 

 during early season and also during late season. We believe 

 that lack of attractiveness of benzaldehyde plus pheromone 

 over the 1 5 days that comprised the mid-season period could 

 have been due, in part, to impact of low temperatures on 

 level of adult activity but also in part to loss of activity of 

 pheromone and altered activity of benzaldehyde, perhaps 

 during the warm days that characterized the preceding early- 

 season period. If the latter is true, then we need to investi- 

 gate a better way of dispensing benzaldehyde to ensure sta- 

 bility and longevity at a desired release rate. 



We conclude that panel and/or pyramid traps baited with 

 benzaldehyde plus pheromone deployed at borders of plum 

 curculio overwintering sites, particularly near areas of or- 

 chards where the greatest plum curculio injury occurs, as 

 determined by previous experience, can be a valuable tool 

 for identifying the pattern of PC immigration. This can aid 

 in accurate timing of insecticide application. The next step 

 will be to work with combinations of odor volatiles, differ- 

 ent release rates, and trap placement in order to improve 

 performance of the ttaps. 



A cknon'lcdgni en ts 



We thank Russ Fleury, Brad Chandler, Katie Bednaz, 

 Amanda Ross, Tracy Leskey, and Juan Rull for assistance. 

 Funds for this work were provided by a USDA Northeast 

 Regional 1PM grant, a Hatch grant, and the New England 

 Tree Fruit Research Committee. 



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Fruit Notes, Volume 65, 2000 



