Establishing Characteristics of 

 Odor-baited Trap Trees for IVIonitoring 

 PlumCurculio 



Ronald Prokopy, Isabel Jacome, Eliza Gray, Guadalupe Trujillo, Mareana 



Ricci, and Jaime Pinero 



Department of Entomology, University of Massachusetts 



In the three preceding articles in this issue of Fruit 

 Notes, evidence was presented that enough plum 

 curculio (PC) adults are present on interior rows of 

 apple trees at petal fall to justify a petal fall application 

 of insecticide to all rows of an orchard block rather 

 than just peripheral rows. In the first article, evidence 

 was also presented to suggest that following a petal 

 fall application of insecticide, subsequent insecticide 

 applications against PC (first/second cover sprays) can 

 provide effective block-wide control if confined only to 

 perimeter rows 1 and 2. The question now arises as to 

 which blocks in an orchard require cover-sprays for 

 perimeter rows and what is the best timing for such 

 perimeter-row sprays. 



In the 2003 Winter issue of Fruit Notes, we 

 reported that penmeter-row apple trees baited with a 

 combination of synthetic attractive pheromone 

 (grandisoic acid) plus synthetic attractive fruit odor 

 (benzaldehyde) could function as "trap trees" that 

 aggregated PC injury. We suggested that sampling for 

 PC injury to ascertain where and when to apply 

 perimeter-row sprays could be restricted to trap trees 

 rather than spread out among many different trees in a 

 block. 



Here, we present results of 2003 experiments 

 addressing five questions relevant to practical 

 implementation of an odor-baited trap tree approach to 

 monitoring PC: (1) what are optimum amounts of 

 grandisoic acid (GA) and benzaldehyde (BEN) to deploy 

 per trap tree; (2) over what distances do trap trees act 

 to aggregate injury to fruit by PCs; (3) does a trap tree 

 at the intersection of two perimeter rows (i.e., at a 

 comer) outperform one midway along a perimeter row; 

 (4) within a trap tree, is fruit injury likely to be greatest 

 in the vicinity of the odor source; and (5) within a trap 

 tree, where should a grower or consultant examine fruit 



to gain a representative sample of injury? 



Materials & Methods 



For all experiments, odor-baited trap trees were 

 located on perimeter rows of blocks of commercial- 

 orchard apple trees in Massachusetts. Tree size, 

 spacing, and cultivar composition were the same for all 

 treatments within a replicate, but these characteristics 

 varied among replicates and experiments. Perimeter- 

 row trees received three or four grower-applied sprays 

 of Guthion or Imidan at label-recommended rate for 

 PC control. Applications commenced in late May, 

 shortly after petal fall and ended in mid or late June. 



BEN was introduced into 1 5 ml capped polyethylene 

 vials in the amount of 8 ml of liquid per vial: 9 parts 

 BEN plus 1 part of 1 , 2, 4-trichlorobenzene as stabilizing 

 agent. Each vial was suspended by wire inside of an 

 inverted red plastic drinking cup to minimize potential 

 negative impact of ultraviolet light on the stability of 

 BEN. Both cup and vial were suspended by wire 

 protruding through the bottom of the inverted cup. Vials 

 deployed in this manner were found to release about 

 10 mg per day of BEN per vial. Each dispenser of 

 pheromone was designed by the manufacturer to 

 release about 1 mg per day of GA. All dispensers of 

 attractive odor were deployed during bloom of apple 

 trees (mid-May) and remained (unrenewed) for 7 

 weeks (through late June), when all experiments ended. 

 Unless indicated otherwise, each trap tree received 

 four dispensers of BEN plus one dispenser of GA hung 

 at head height near the tree trunk. 



In all experiments, PC response to treatments was 

 assessed by examining fruit for signs of ovipositional 

 injury, which comprises 90% or more of all injury to 

 apples by PC. Sampling in each experiment occurred 



Fruit Notes, Volume 69, Winter, 2004 



