Conclusions 



Circle traps baited with benzaldehyde plus GA, 

 when positioned so as to completely surround trunks 

 of perimeter-row apple trees, captured numerically 

 more PC's than any other trap type and afforded a strong 

 positive correlation between total amount of trap 

 captures and total amount of PC injury to perimeter- 

 row fruit. The year 2001 was the first year we used 

 Circle traps in this position on a tree (formerly they 

 were placed on lower limbs near the trunk and provided 

 a weaker correlation between total captures and total 

 injury). The strong correlation obtained in 2001 

 suggests that tree-trunk Circle traps baited with 

 benzaldehyde plus GA, if distributed along perimeter- 

 row apple trees, can be an excellent indicator of "hot 

 spots" requiring special attention for controlling PC 

 as well as "cool spots" requiring lesser attention. 



Unfortunately, no trap type showed even a 

 moderate positive relationship between the time of 

 occurrence of PC captures and the time of occurrence 

 of PC injury to fruit. As depicted in Figure 4, even for 

 our best trap type (tree-trunk Circle traps baited with 

 benzaldehyde plus GA), captures fell off dramatically 

 soon after petal fall, whereas fruit injury rose steadily. 

 Thus, even for this best trap, the data obtained in 200 1 

 indicate that low trap captures after petal fall cannot 

 be relied upon as indicative of the lack of need to spray 

 against PC. 



As revealed by other studies that we conducted in 

 2001 , there are at least three reasons why all three types 

 of traps used here may fail to capture representative 

 numbers of PC's active in canopies of commercial 

 orchard trees after petal fall. First, organophosphate 

 insecticide spray droplets falling on traps can be 

 repellent to PC's for 10 days or more after application. 

 Such droplets can also be repellent when on tree limbs 

 and branches, but repellency apparently is substantially 

 overcome by positive chemical stimuli inherent to 

 surfaces of limbs and branches. Such positive stimuli 

 are lacking on surfaces of current traps. Second, at 

 temperatures greater than about 70°F, especially when 

 accompanied by sun, PC's tend to fly directly into tree 

 canopies, thereby bypassing Circle and pyramid traps 

 associated with tree trunks. Temperatures tend to be 



higher than 70°F after petal fall. Third, the release rate 

 of benzaldehyde from vials placed inside of trap tops 

 ( 1 milligrams per day) is sufficient to attract PC's from 

 a distance, but may be repellent at close range. As tree 

 fruit grow and themselves release increasing amounts 

 of benzaldehyde and other attractants, there may be an 

 increasing tendency for attractive volatiles from the 

 fruit to outcompete attractive volatiles placed in traps. 

 Our attempts to increase the amount of benzaldehyde 

 used in association with traps, so as to be more 

 competitive with fruit volatiles, have been accompanied 

 by a decrease (rather than an increase) in PC captures 

 owing to repellency. Together, these three shortcomings 

 may limit the usefulness of Circle, pyramid, and 

 cylinder traps placed at or within canopies of 

 commercial-orchard trees for monitoring the extent of 

 threat by PC's after petal fall. 



Both cultivar composition of perimeter-row trees 

 and border area composition had an influence on extent 

 of trap captures and fruit injury by PC. As in 2000, 

 perimeter-row trees of Gala, Jonagold, or Fuji 

 experienced considerably more PC pressure than 

 perimeter-row trees of Mcintosh or Empire, even 

 though there was no difference in frequency of 

 insecticide applications. Also, as in 2000, trap captures 

 were greater in blocks bordering woods than in blocks 

 bordering hedgerows or open field. Finally, PC injury 

 to fruit on trees that received traps was far greater than 

 PC injury to fruit on interior trees, suggesting that 

 attractive odor placed on perimeter-row trees acts to 

 concentrate PC's there and reduce penetration into the 

 orchard interior. 



Ackno wledgm ents. 



We are grateful to the following growers for 

 participating in this study: Keith Arsenault, Gerry 

 Beime, Bill Broderick, Dave Chandler, Tom Clark, Don 

 Green, Tony Lincoln, Joe Sincuk, Mo Tougas, and 

 Steve Ware. This work was supported by Massachusetts 

 State Integrated Pest Management Funds, Northeast 

 Regional Competitive Integrated Pest Management 

 Funds, Northeast Regional Sustainable Agricultural 

 Research and Education Funds, and the New England 

 Tree Fruit Growers Research Committee. 



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22 



Fruit Notes, Volume 67, Winter, 2002 



