Devising an Attractive Bait to IVIonitor 

 the Seasonal Course of Plum Curculio 

 Immigration into Apple Orchards 

 using Traps 



Jaime Piiiero, Sara Hoffman, Everardo Bigurra, and Ronald Prokopy 

 Department of Entomology, University of Massachusetts 



To reduce insecticide use against plum curculio 

 (PC), management strategies should consider the time 

 of first appearance of PCs on host trees after 

 overwintering in woods, as well as the peak and the 

 end of immigration. One approach to tracking the 

 seasonal course of PC immigration is the use of a trap 

 baited with a lure that is highly attractive to PCs. In 

 the 2000 issue of Fruit Notes, we reported that both 

 panel and pyramid traps baited with benzaldehyde 

 (BEN) in combination with PC pheromone called 

 grandisoic acid (GA) were very good indicators of the 

 seasonal course of immigration into apple orchards 

 when deployed in close proximity to woods. In that 

 study, we also found that ethyl isovalerate (EIV) and 

 limonene (LIM), in combination with GA, showed 

 some degree of attractiveness to PCs, but to a lesser 

 extent when compared to the high luring power of 

 BEN+GA. 



Here, we report on two field studies performed in 

 Massachusetts in 2001 and 2002 using panel and 

 pyramid traps. The 2001 study was aimed at evaluating 

 the three most attractive fruit odors (BEN, EFV, and 

 LIM) found in our 2000 study to confirm the high 

 attractiveness of the combination BEN+GA to PCs. The 

 2002 study was performed to evaluate PC response to 

 four different amounts of BEN (the most attractive fruit 

 odor found in the 2001 study) and two different 

 amounts of GA to determine the amount of each odor 

 needed to maximize the performance of monitoring 

 traps. 



Materials & Methods 



Both studies were conducted in an unsprayed 

 section of a commercial apple orchard at the UMASS 



Cold Spring Orchard Research & Education Center 

 (Belchertown, MA). As in 2000, traps evaluated in 200 1 

 and 2002 were clear Plexiglas panels (2x2 feet, with 

 the woods-facing side coated with Tangletrap) and 

 black pyramid traps (24 inches wide at base x 48 inches 

 tall) (Figure 1). Whereas panel traps capture mainly 

 PCs in flight (particularly on warm days), pyramid traps 

 capture primarily crawling PCs (mostly during cool 

 days or at night). 



2001 Study. This study was undertaken from April 

 30 to June 30, 2001. Host plant odors evaluated were 

 benzaldehyde (BEN), ethyl isovalerate (EFV), and 

 limonene (LIM), all purchased from Sigma-Aldrich 

 Chemical Co. (Milwaukee, WI). Three different groups 

 of odor treatments were arranged, each involving a 

 single host volatile alone, GA alone, a combination of 

 host volatile and GA, and a no-odor (control) treatment. 

 By testing each fruit odor alone and in combination 

 with GA, we sought to determine the extent to which 

 each of the synthetic host plant volatiles tested 

 enhanced PC responsiveness to GA. There were four 

 replicates for each trap type and odor combination. 



BEN was released from 1-ml low-density white 

 polyethylene vials in order to prevent polymerization 

 of this chemical by UV light (as found in 2000 when 

 using high-density clear polyethylene vials). Because 

 this problem was not found for EFV and LIM, these 

 two chemicals were tested (as in 2000) using 400 'Al 

 high-density clear polyethylene vials. A white vial filled 

 with 1 ml of BEN released -2.5 mg/day of BEN. Only 

 one vial of this type was used per trap. Two vials 

 containing LIM and three vials containing EIV were 

 needed per trap to accomplish a release rate of ~10 

 mg/day of each chemical. Each pheromone dispenser 

 released ~1 mg/day of GA. 



Fruit Notes, Volume 67, Fall, 2002 



13 



