heightened part-way through our field tests 

 when a pubhcation appeared by chemists in 

 Ilhnois detaihng the chemical structure of a 

 pheromone (grandisoic acid) produced by male 

 plum curculios that is equally attractive to both 

 females and males, even when used in small 

 amounts. This was indeed exciting news. Our 

 follow-up laboratory tests showed, however, 

 that when curculios are confined to small areas 

 (such as the containers we used for curculios as 

 odor sources), they emit stress sounds and/or 

 odors alerting other curculios. These sounds or 

 odors apparently mask or outweigh the luring 

 power of attractive pheromone. This suggests 

 that the most rewarding way to evaluate 

 pheromonal odor in conjunction with traps in 

 the field would be to use synthetic pheromone 

 rather than a natural source of pheromonal 

 odor. 



In the case of apple odor as bait, it appears 



that if natural sources of odor are used in the 

 amounts evaluated here, either such an 

 amount is insufficient to compete with fruit 

 odor sources on adjacent trees, or natural 

 sources of apple odor lose attractiveness (odor 

 composition changes) rapidly after employ- 

 ment. As with synthetic sex pheromones, 

 sjrnthetic apple odor hopefully will become an 

 effective alternative to natural sources of apple 

 odor for attracting plum curculios to traps (see 

 following article). 



Acknowledgments 



This work was supported by grants from the 

 USDA Northeast Regional IPM Competitive 

 Grants Program, State/Federal IPM funds, the 

 USDA SAKE Program, and the New England 

 Tree Fruit Growers Research Committee. 



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12 



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



