Bloom 



5 Wks 



6 Wks 



Figure 1. Response Indices for plum curculio adults during 2 hours of exposure to 

 hexane extracts of twigs (diamonds), leaves (squares), or fruit (triangles) from 

 Mcintosh trees at pink, bloom, petal fall, or 2, 3, 4, 5, or 6 weeks after bloom. If the 

 difference between two means of any stage exceeds 16 (based on a sample size of 

 12), then the means are significantly different at odds of 19 to 1. 



(index = 58), whereas extracts of Mcintosh 

 leaves were marginally attractive (index = 25), 

 most likely because the waxy layer on leaf 

 surfaces prevented water from extracting 

 volatile components. Again, both males and 

 females responded equally well to extracts 

 made with water. 



Conclusions 



From these results and from what we 

 observed in 1995, we conclude that petal fall is 

 the most attractive developmental stage of 

 Mcintosh trees to plum curculio adults. 

 Further, we believe that all Mcintosh plant 

 tissues (twigs, leaves, and fruit) contain the 

 attractive odor components at this time. These 

 results further strengthen our hope that 

 synthetic equivalents of these attractive 

 Mcintosh plant odors can be identified and 



synthesized, providing tools to enhance trap 

 effectiveness for monitoring and possibly even 

 controlling plum curculios. Further, were 

 believe that if synthetic host odors can be used 

 in conjunction with synthetic male-produced 

 pheromone identified in 1996 by Eller and 

 Bartlett of Illinois, the curculio-capturing 

 power of traps will be enhanced further. Our 

 next step will be to examine curculio responses 

 to host-plant odors used in combination with 

 male-produced pheromone. 



Acknowledgments 



This work was supported by grants from the 

 USDA Northeast Regional IPM Competitive 

 Grants Program, the USDA SARE Program, 

 State/Federal IPM funds, and the New 

 England Tree Fruit Growers Research Com- 

 mittee. 



14 



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



