An Odor-baited "Trap-tree" Approach to 

 Monitoring Plum Curculio 



Ronald Prokopy 



Department of Entomology, University of Massachusetts 



As described in the preceding article, there are 

 shortcomings associated with placement of plum 

 curculio (PC) monitoring traps in commercial orchards 

 for purposes of determining when a spray is needed to 

 protect fruit against PC damage. Shortcomings are 

 particularly evident during the middle and latter part 

 of the PC season, when trap captures remain low 

 irrespective of trap type or attractive odor, but damage 

 increases. One of the principal shortcomings involves 

 need for baiting traps with an increasing amount of 

 synthetic attractive fruit odor as the PC season 

 progresses in order that odor might compete effectively 

 with the increasing amount of attractive odor emitted 

 by developing fruit in the tree canopy. When used in 

 association with traps, increasing amounts of synthetic 



fruit odor become repellent at close range. 



One possible solution to this dilemma could be to 

 create a "trap tree" where the tree canopy itself is baited 

 with a high amount of attractive fruit odor. Rather than 

 using amounts of PC's captured by traps as a potential 

 but indirect indicator of level of PC egglaying activity, 

 one would use amount of freshly injured fruit on the 

 trap tree as a direct indicator. A few such trap trees per 

 orchard could provide valuable information on sudden 

 rises in PC damage and hence on the need to apply a 

 protective spray. Placement of attractive odor directly 

 on tree branches would eliminate problems of close- 

 range repellency associated with placement of odor on 

 or in traps. 



In 200 1 , 1 conducted a preliminary trial of this new 



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 U. LU 



HI 



3 



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6 -I 



5 - 



4 - 



3 - 



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■ BAITED TREES 

 dUNBAITED TREES 





WEEKS AFTER PETAL FALL 



Figure 1. Amount of fruit injured by plum curculio on baited perimeter-row trap trees 

 and on unbaited trees midway between trap trees. 



Fruit Notes, Volume 67, Winter, 2002 



23 



