Optimizing Distances Between Odor- 

 baited Spheres on Perimeter Apple 

 Trees for Control of Apple Maggot Flies 



Ronald Prokopy, Isabel Jacome, and Everardo Bigurra 



Department of Plant, Soil, & Insect Science, University of Massachusetts 



For several decades, spraying apple trees with 

 insecticide in July and August has been the standard 

 approach to apple maggot fly (AMF) control. While 

 this approach is likely to continue to be the standard in 

 most orchards for decades to come, some growers 

 would like an alternative approach that eliminates the 

 need for insecticide application during summer months. 

 One alternative that we have been studying for more 

 than a decade is the surrounding of orchard blocks with 

 odor-baited spheres on perimeter apple trees to 

 intercept immigrating AMF before they can penetrate 

 into interior rows. 



hi the Spring 2002 issue oi Fruit Notes, we reported 

 that the most effective odor bait to use in conjunction 

 with perimeter spheres for maximizing AMF control 

 under a broad range of orchard conditions is a five- 

 component blend of synthetic attractive apple volatiles 

 developed at Cornell University. In other issues of Fivil 

 Notes preceding 2002, we presented data suggesting 

 that odor-baited spheres deployed on perimeter trees 

 may be more effective (a) in orchards comprised of 

 small or medium trees than in orchards of large trees, 

 (b) in orchards having particular arrangements of 

 susceptible versus tolerant cultivars, and (c) in orchards 

 bordered by open space than by hedgerow or woods. 

 In addition, we suspected that sphere effectiveness 

 might be greater in well-pruned than poorly-pruned 

 perimeter trees. 



To qualify as a viable alternative to spraying an 

 orchard for AMF control, use of odor-baited spheres 

 on perimeter trees must be cost-competitive; the fewer 

 the number of spheres needed, the less the cost. Until 

 now, distances between perimeter spheres in apple 

 orchards have been assigned largely on an arbitrary 

 basis (devoid of established guiding principles), varying 

 from 2 to 45 yards apart. 



Here, we developed an approach to assigning 



distances between odor-baited spheres or perimeter 

 trees of apple orchards. It employs an index 

 incorporating characteristics of four environmental 

 variables: size of orchard trees, quality of pruning, 

 cultivar composition and nature of bordering habitat. 



Materials & Methods 



Block layout. Our experiment was conducted in 

 12 blocks of apple trees in ten commercial orchards in 

 Massachusetts. Each block consisted of seven rows 

 of apple trees, was about 120 yards long, and averaged 

 35 yards deep in extension from a perimeter row that 

 bordered open field, hedgerow, or woods to the seventh 

 interior row. Each block was divided into two plots: 

 one plot about 90 yards long, the other about 30 yards 

 long. Blocks consisted of either small (M.9 rooted), 

 medium (M.26 rooted), or large (M.7 rooted) trees that 

 were either well, moderately, or poorly pruned in 2003. 

 Each row of a block was comprised of the same cultivar, 

 which was considered as being of relatively low 

 susceptibility to AMF if Mcintosh or Empire, moderate 

 susceptibility if Cortland or Delicious, and high 

 susceptibility if Fuji, Gala, or Jonagold. Each of the four 

 sides of a block was bordered by grower-sprayed 

 orchard trees, open field, hedgerow, or woods. 



Pesticide sprays. Each plot in each block was 

 sprayed by cooperating growers with insecticide and 

 fungicide in April, May, and June to control a variety of 

 insects and diseases. Thereafter, the smaller (30 x 35 

 yards) plot received two or three grower-applied sprays 

 of insecticide in July and August to control AMF; 

 whereas, the larger (90 x 35 yards) plot received no 

 insecticide after June but received odor-baited spheres 

 to control AMF. 



Spheres. Each sphere trap was 3.5 inches in 

 diameter, red in color, and coated with Tangletrap to 



10 



Fruit Notes, Volume 69, Spring, 2004 



