12 - 



10 ■ 



E 



z 



■ Scars 



D Captured Adults 



♦ Insecticide Application 



r M I 



6-Jun 8-Jun 



10-Ju 



12-Jun 14-Jun 



23-May 25-May 27-May 29-May 31 -May 2-Jun 4-Jun 



Figure 2. Egg-laying scars and trap captures from May 23 through June 15, 1996. 



tree canopy and trunks. 

 Results 



Unbaited pyramid traps placed adjacent to 

 tree trunks captured at least five times more 

 curculios than unbaited pyramid traps at any 

 other position and 15 times more curculios than 

 unbaited boll weevil trap tops placed in tree 

 canopies (Table 1). 



Capture of substantial numbers of curculios 

 by unbaited pjn-amid traps next to tree trunks 

 could entice one to believe that such captures 

 might be used as a basis for determining need 

 for and timing of insecticide sprays against 

 curculio. Unfortunately, this did not prove to be 

 the case in the Conway orchard in 1996. In fact, 

 there was no trap position for which there was 

 even a faint positive correlation between daily 



trap captures and daily numbers of sampled 

 fruit injured by plum curculios. Indeed, the 

 correlation between daily captures by pyramid 

 traps at tree trunks and daily fruit injuries was 

 a negative rather than a positive one (Figure 2). 

 In other words, during periods when captures 

 were greatest, injury was least. 



Conclusions 



Our findings show that placing black 

 pyramid traps next to apple tree trunks is the 

 most effective position in terms of capturing the 

 greatest numbers of plum curculios in an apple 

 orchard. Results of additional studies (see 

 following article) indicate that the principal 

 reason why this position is better than any 

 other position stems from the strong tendency 

 of curculios, when crawling, to move toward 



Fruit Notes, Volume 62 (Number 1), Fall, 1997 



