Optimal Positioning of Baited Sticky 

 Red Spheres for Capturing Apple 

 Maggot Flies 



Jian Jun Duan, Max P. Prokopy, Paul Des Georges, 



and Ronald J. Prokopy 



Department of Entomology^ University of Massachusetts 



In a previous article [Fruit Notes 56(4): 4-6], we 

 reported that a combination of food odor (ammonia) 

 and fruit odor (butyl hexanoate) significantly in- 

 creased apple maggot fly (AMF) captures on three- 

 inch baited red sticky spheres, thus enhancing the 

 effectiveness of interception traps currently used in 

 the second-level IPM program. Past studies by 

 Reissig (1975) and Drummond et £il. (1984) showed 

 that AMF captures on unbaited spheres were influ- 

 enced significantly by position of spheres in the tree 

 canopy, including height above ground, proximity 

 to fruit and foliage, and distance from the outside 

 edge of the tree canopy. We predicted that these 

 variables would have less influence on AMF cap- 

 tures on sticky spheres baited with food and fruit 

 odor than on unbaited spheres. Here we report on 

 studies testing this prediction. 



Materials and Methods 



Three experiments were conducted in 1992 in 

 second-level IPM orchards (commercial orchards 

 not sprayed with insecticide after early June). We 

 first investigated the optimal distance of fruit and 

 foliage from spheres not baited or baited with one 

 dispenser of ammonium acetate and one two-dram 

 polyethylene vial of butyl hexanoate (Experiment 

 1). We next studied the effects of presence vs. 

 absence of fruit within 20 inches of unbaited spheres 

 or spheres baited with the same types of odor as in 

 Experiment 1 (Experiment 2). In Experiment 3, we 

 investigated the influence of height of sphere place- 

 ment in the tree canopy on the efficacy of spheres 

 not baited or baited with one polyethylene vial of 

 butyl hexanoate. 



Experiments 1 and 2 were conducted in 

 Clarkdale Fruit Farm, West Deerfield, MA, which 

 consisted of a mixture of 25-year-old Early Mcin- 

 tosh and Gravenstein trees. The trees were about 12 



to 16 feet in canopy diameter. In Experiment 1, we 

 hung four sticky spheres in each of ten trees and 

 removed the foliage and fruit surrounding the spheres 

 to distances of 2, 10, 20, or 40 inches. On five of the 

 trees, we placed one dispenser of ammonium acetate 

 (about 5 grams) and one vial of butyl hexanoate 

 (about 5 milliliters) about six inches from the sphere. 

 Spheres on the other five trees were not baited with 

 any type of odor. In Experiment 2, we placed two 

 sticky spheres in each of 14 trees. On seven of the 

 trees, spheres were baited with ammonium acetate 

 and butyl hexanoate in the same manner as in Ex- 

 periment 1. Spheres on the other seven trees were not 

 baited. One of the two spheres in each tree was 

 cleared of all fruit within 10 inches. The other sphere 

 was cleared of all fruit within 20 inches. The foliage 

 surrounding each sphere was removed within a con- 

 stant distance of 10 inches. 



Experiment 3 was conducted at the University of 

 Massachusetts Horticultural Research Center, 

 Belchertown, MA, in a block of four-to-five-year-old 

 Liberty trees having a canopy three to five feet in 

 diameter and a height of six to eight. In this experi- 

 ment, we placed only one sphere (either not baited or 

 baited with one polyethylene vial of butyl hexanoate) 

 on each tree. Spheres were placed in trees at three 

 different heights: upper 1/3, middle 1/3, or lower 1/3 

 of the canopy. Foliage and fruit within 10 inches of 

 each sphere were removed. 



For all experiments, captured male and female 

 AMF were counted and spheres were cleared of all 

 insects captured every two weeks. In Experiments 1 

 and 2, unbaited and baited spheres were emplaced on 

 July 28 and rotated among trees at each examination 

 (every two weeks) until September 8, when the test 

 ended. Experiment 3 began on July 27 and ended on 

 September 11. Spheres were not rotated among 

 trees. 



Fruit Notes, Summer, 1993 



