Evaluation of Unbaited PyramidTraps for 

 Monitoring Plum Curculio in Commercial 

 Apple Orchards 



Ronald Prokopy, Michael Marsello, Tracy Leskey, and Starker Wright 

 Department of Entomology, University of Massachusetts 



In the 1997 Winter issue of Fruit Notes, we 

 reported on a 1996 study evaluating unbaited 

 black pyramid traps as devices for capturing 

 plum curculio adults and predicting need and 

 timing of insecticide sprays against plum 

 curculio based on trap captures. That study, 

 conducted in a small commercial apple orchard 

 in Conway, showed that even though black p5Ta- 

 mid traps in optimum positions (next to apple 

 tree trunks) captured reasonable numbers of 

 plum curculios, there was no correlation be- 

 tween periods of substantial capture and peri- 

 ods of substantial damage by curculios to fruit. 

 In other words, trap captures were poor predic- 

 tors of when insecticides should be applied 

 against curculio in that orchard in 1996. Black 

 pyramid traps, intended to mimic tree trunks, 

 are currently receiving much attention as po- 

 tential monitoring devices for plum curculio in 

 peach orchards in the South. 



Here, we report on a study in which black 

 pyramid traps were evaluated at three positions 

 in eight large commercial orchards in Massa- 

 chusetts in 1997. 



Materials and Methods 



Pyramid traps were the same as used in 

 1996 and were a modification of traps designed 

 for monitoring pecan weevils in the South. 

 Three traps were placed in each of six blocks of 

 apple trees in each of eight commercial orchards. 

 All blocks contained 49 trees (seven rows of 

 seven trees each) of mixed cultivars of fruit- 

 bearing age. Of the six blocks per orchard, there 

 were two blocks each of trees on M.9, M.26, and 

 M.7 rootstock, giving rise to what we term here 



as small, medium, and large trees, respectively. 

 For each block, one trap was placed within 30 

 cm of the tree trunk (termed trunk trap) of a 

 perimeter tree, one mid-way between the 

 canopy of a perimeter tree and the first inte- 

 rior tree (termed inter-tree trap), and one at the 

 margin of the nearest woods (termed border 

 trap). The ground beneath and between orchard 

 trees was either free of b vegetation or vegeta- 

 tion was mowed to prevent obscuring of traps. 

 Traps were deployed during bloom and were 

 examined for captured plum curculio adults ev- 

 ery 3-4 days thereafter for 4-5 weeks. At each 

 trap examination, beginning at petal fall, 15 

 fruit per tree of each of the seven perimeter trees 

 were examined for presence of plum curculio 

 oviposition scars (total of 105 fruit per block per 

 sampling date). Scarred fruit were allowed to 

 remain on the tree. All blocks received either 

 two or three grower-applied sprays of Guthion 

 or Imidan, beginning at petal fall and 8-11 days 

 later(second spray), as well as 16-20 days (third 

 spray) thereafter. Growers applied sprays ac- 

 cording to their own estimation of need, with- 

 out access to our data for making application 

 decisions. To protect against insecticide, a plas- 

 tic bag was used to envelope each trap com- 

 pletely just before spraying and was removed 

 immediately thereafter. This was done because 

 in a preliminary test, only about 40% as many 

 curculios (0.8 vs. 1.9 per trap, a significant dif- 

 ference) were captured by traps sprayed with 

 Imidan as by unsprayed traps. 



Results 



We combined data for the two blocks of simi- 



Fruit Notes, Volume 63 (Number 1), Winter, 1998 



