negative effects while preserving (or even enhancing) 

 attractiveness to PCs. Results from experiment 4 

 (involving Circle traps), in which vials were placed 

 outside of trap tops, further support this conclusion. 



Third, 1-ml white vials releasing benzaldehyde 

 were found to perform best during the first 8 days after 

 deployment (experiment 3) and, after that time, their 

 attractiveness decreased considerably. A close 

 examination of the 1-ml white polyethylene vials 

 revealed the formation of whitish/yellowish crystals 

 m the area of necks of vials after 8 days of use. In 

 contrast, the 15-ml white polyethylene vials used in 

 experiment 4 showed no signs of such crystals on any 

 parts of the vials after one week (experiment 4) or 

 several weeks (data from other field studies) of use. 

 This difference may be due largely to the type of screw 

 cap used in association with the white vials in each 

 year. In 2001, the 1-ml white polyethylene vials were 

 enclosed by white polypropylene caps that lacked 

 Teflon® liner as a sealant, and thus oxygen may have 

 interacted with benzaldehyde altering its chemical 

 composition. On the contrary, in 2002 the 1 5-ml white 

 vials were enclosed by black phenolic Teflon®-lined 

 caps, which apparently prevented oxygen from 

 interacting with the benzaldehyde contained in the 

 vials. Also, in 2002 the use of plastic cups provided 

 extra protection against UV light and rainfall. 



Fourth, results from the fourth experiment strongly 

 suggest that there was an increase in PC captures by 

 Circle traps associated with an increase in the 

 concentration of benzaldehyde. In this experiment, the 

 maximum release rate of benzaldehyde tested was -40 

 mg per day. Hence, it is possible that even higher 

 amounts of benzaldehyde may increase the 

 attractiveness of benzaldehyde to PCs. This aspect is 

 particularly important not only in relation to the 

 determination of amount of benzaldehyde to be used 

 to bait traps to monitor the onset, course, and end of 

 PC immigration, but also to the determination of 

 amount of benzaldehyde to be employed in perimeter- 

 row odor-baited trap trees (see the 2002 winter issue 

 of Fruit Notes) to follow accurately the course of plum 

 curculio injury to fruit in commercial apple orchards 

 in Massachusetts. 



Acknowledgments 



We thank Everardo Bigurra and Phillip McGowan 

 for field assistance. This study was supported with 

 funds provided by a USDA Northeast Regional IPM 

 grant, a Hatch grant, a grant from USDA Crops at Risk 

 program, and the New England Tree Fruit Research 

 Committee. 



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Fruit Notes, Volume 67, Fall, 2002 



