Perhaps apples and red spheres increasingly larger 

 than 8 cm decreasingly have the appearance of fruit in 

 the eyes of flies whose native host is hawthorn fruit, 

 which are only 1.5 to 2.0 cm in diameter. 



The second study involved evaluation of different 

 numbers of vials containing synthetic apple odor 

 placed at different distances from 8 cm sticky red 

 spheres. At the New York Agricultural Experiment 

 Station in Geneva, where Anne Averill, Harvey Reis- 

 sig, Wendell Roelofs, and others showed butyl hex- 

 anoate to be the principal component of apple odor 

 attraction to apple maggot flies, liquid butyl hexanoate 

 has been used to monitor fly populations by putting it 

 into small (2-dram) polyethylene vials seated in wells 

 drilled into 8 cm red spheres. The liquid is absorbed by 

 the wall of the vial, which then releases about 700 apple 

 equivalents of the odor per hour. In the first 2 years of 

 our pilot second-stage apple IPM program, we placed 

 such a polyethylene vial containing butyl hexanoate 

 about 15 cm to the side of each 8 cm sticky red sphere 

 hung on perimeter apple trees. However, recent re- 

 search conducted by graduate student Martin Aluja of 

 our laboratory suggested that a polyethylene vial re- 



Table 2. Total apple maggot females captured on 8 cm 

 sticky red spheres hung in fruiting apple trees in a com- 

 mercial orchard and baited with different numbers of 2- 

 dram polyethylene vials containing attractive apple odor 

 (butyl hexanoate) at different distances from the side of a 

 sphere (July 21 - August 3, 1989). 



Distance of vials 

 from sphere (cm)* 



Number of vials around each sphere 



15 



30 



60 



47 b 70 b 92 b 78 b 



67 b 66 b 149 a 92 b 



70 b 83 b 96 b 101 b 



leasing 700 apple equivalents of butyl hexanoate per 

 hour may arrest or even repel apple maggot flies that 

 move too close to the vial. We were therefore interested 

 in determining the optimum density and distribution 

 of polyethylene vials (containing butyl hexanoate) that 

 would confer high fly attraction to the vicinity of a red 

 sphere but not adversely affect the propensity of an 

 arriving female to alight on the sphere. 



Our test was carried out in Clarkdale Orchard, 

 West Deerfield, MA, which harbored a moderate popu- 

 lation of apple maggot flies on a mixture of Early 

 Mcintosh and Gravenstein test trees. We placed no 

 more than 1 sphere in each tree. Using wire, we posi- 

 tioned either 0,1,2, or 4 2-dram polyethylene vials of 

 butyl hexanoate 15,30, or 60 cm to the side of a sphere. 

 Where more than 1 vial per sphere was used, vials were 

 distributed evenly around the sphere. Periodically, the 

 vials were rotated from tree to tree to provide equal 

 time for each treatment at each position. 



The results (Table 2) indicate that 2 vials of odor 

 placed 30 cm to the side of a red sphere gave rise to a 

 50% greater capture of apple maggot females than vials 

 at any other density or distribution. Use of 2 or 4 vials 

 per sphere invariably led to greater fe- 

 male captures than vials or 1 vial at an 

 equivalent distance. Thus, butyl hex- 

 anoate used in conjunction with red 

 spheres led to increased capture of apple 

 maggot females, but too great an amount 

 too close to a sphere reduced fly captures, 

 possibly through arresting or repelling ef- 

 fects. 



For future employment of red 

 spheres to intercept apple maggot flies on 

 perimeter apple trees under second-stage 

 IPM, we will continue to use 8 cm spheres 

 but will now bait each sphere with two 2- 

 dram polyetheylene vials of butyl hex- 

 anoate 30 cm from (and on opposite sides 

 of) each sphere, instead of a single vial 15 

 cm from a sphere. 



• Four replicates per treatment type. Values not followed 

 by the same letter are significantly different at odds of 19 

 to 1. 



ACKNOWLEDGMENT. We thank 

 the Northeast Regional Project on Inte- 

 grated Management of Apple Pests (NE- 

 156) for supporting this work. 



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Fruit Notes, Fall, 1989 



19 



