Extent of Early-season Plum Curculio 

 Penetration into Commercial 

 Apple Orchards 



Jaime Pinero, Isabel Jacome, Everardo Bigurra, Guadalupe Trujillo, and 



Ronald Prokopy 



Department of Entomology, University of Massachusetts 



In the first article in this issue oi Fruit Notes, we 

 evaluated the effectiveness of peripheral-row vs. all- 

 row sprays in controlling plum curculios in New England 

 apple orchards. We proposed two possibilities to explain 

 why confining sprays exclusively to peripheral rows 

 led to unacceptable PC control. In the preceding article, 

 we provided information supporting the first possibility: 

 some PCs are able to overwinter inside of orchards, 

 and thereby they may escape sprays applied only to 

 peripheral rows against immigrant adults. We suggested 

 that one of the main factors influencing the amount of 

 ovei-wintenng inside orchards might be type of orchard 

 management, such as presence of vegetation beneath 

 orchard trees, particularly during the period of time at 

 which adult PCs seek overwintering sites in the autumn. 

 Here, we report results of a study conducted in 2003 

 aimed at addressing the second possibility. We asked 

 whether PCs overwintering in woods or hedgerows 

 outside of orchards move into interior rows of orchards 

 before petal fall and thereby escape effects of petal 

 fall and subsequent sprays when they are confined only 

 to peripheral rows. 



Materials & Methods 



This study was performed during April/May of 2003 

 in eight commercial apple orchards in Massachusetts. 

 Within each orchard, blocks selected had similar length 

 (about 200 yards of perimeter-row trees) and depth (at 

 least 80 yards). For each block, trees used were of a 

 particular size: either large (M.7 rootstock), medium 

 (M.26 rootstock), or small (M.9 rootstock). 



For this study we used Circle traps (originally 

 developed by Edmund Circle, a pecan grower in 



Oklahoma), which are made of either aluminum or vinyl- 

 coated polyester screen with a PC-capturing device 

 integrated on top. Traps are wrapped around the base 

 of tree trunks so as to completely encircle the trunk, 

 thereby intercepting adults walking upward. 



For each selected block, 20 Circle traps were 

 deployed on April 24 (at the green-tip tree stage) on 

 trees located in the central part (about 60-70 yards in 

 length) of each orchard to minimize potential penetration 

 of PCs from the lateral or back sides (Figure 1). For 

 each block, traps were arranged in four transects of 

 five traps each, starting on perimeter-row trees. 

 Because there were different inter-row distances and 

 tree densities due to the different tree sizes, blocks 

 having large trees received traps deployed in 

 consecutive rows (1-5), blocks having medium-sized 

 trees received traps deployed in rows 1,3,5, 7, and 9, 

 and blocks having small trees received traps deployed 

 in rows 1,4,7, 10, and 1 3 . Under this approach, traps 

 were deployed at similar distances mside a block: on 

 perimeter-row trees (A), and on trees about 12, 22, 32 

 and 42 yards inside of perimeter-row trees (B-E) 

 (Figure 1). 



On May 8 (at mid-pink), traps corresponding to 

 two of the four transects in each block were baited 

 with one dispenser of PC pheromone (grandisoic acid, 

 releasing 1 mg per day) (GA) in association with one 

 dispenser releasing the attractive host plant odor 

 benzaldehyde (BEN) at a very low release rate (2.5 

 mg/day). Traps for the two remaining transects per 

 block were left unbailed (Figure 1). Results show 

 combined captures (baited + unbailed traps) because 

 no differences in captures by either baited or unbailed 

 traps were found. All traps were inspected for PCs on 



Fruit Notes, Volume 69, Winter, 2004 



