Table 1 . Average number of apple maggot flies captured on baited or unbaited sticky red spheres hung in 

 fruiting trees and surrounded at different distances by foliage and/or fruit (July 28 - September 8, 1992).^ 



^ Five replicates per treatment type in Experiment 1 and seven replicates in Experiment 2. Values within 

 columns and within experiment followed by the same letter are not significantly different at odds of 19:1. 



Results 



The results of Experiment 1 (Table 1) showed 

 that for both baited and unbaited spheres, nearly 

 twice as many AMF were captured on spheres with 

 foliage and fruit cleared to a distance of 10 to 20 

 inches compared with 2 or 40 inches. Baited spheres 

 captured 25 to 50% more flies than unbaited spheres 

 at each distance. A previous study by Martin Aluja 

 showed that fruit odor attracts flies from long dis- 

 tances to a host tree or a portion of a host tree, but 

 once a fly arrives on a tree, it primarily will use 

 vision to find an individual fruit or fruit-odor-baited 

 sphere. Surrounding foliage and fruit which influ- 

 ence the visibility of a fruit-odor-baited sphere would 

 therefore influence the probability of a fly finding 

 the sphere. Until our test here, however, we had no 

 knowledge that addition of food odor would fail to 

 overcome the need for making a sphere conspicuous 

 to AMF. 



The results of Experiment 2 (Table 2) indicated 



that when the surrounding foliage was cleared to a 

 constant distance of 10 inches from a sphere, spheres 

 cleared of all fruit within 10 inches captured 33% 

 (unbaited) and 35% (baited) more flies than spheres 

 cleared of all fruit within 20 inches. Possibly, fruit at 

 10 to 20 inches from a sphere attracted more AMF 

 (either by visual or odor stimuli) toward the sphere 

 than fruit 20 inches or further did. 



Results of Experiment 3 (Table 2) showed that 

 for unbaited as well as baited spheres, spheres 

 placed in the upper 1/3 or the middle 1/3 of the tree 

 canopy captured about three times more AMF than 

 spheres placed in the lower 1/3 of the canopy. DiflFer- 

 ences in performance of spheres at the lower versus 

 the middle or upper tree positions were greater than 

 differences between baited and unbaited spheres at 

 any height. Diffierences in AMF captures on both 

 unbaited and baited spheres among different tree 

 canopy heights likely stem from fruit-foraging be- 

 havioral patterns of AMF within trees. A recent 



Table 2. Average number of apple maggot flies captured on baited or unbaited sticky red 

 spheres hung in fruiting trees at different tree canopy heights (July 27 -September 11,1 992).^ 



^ Fourteen replicates per treatment type. Values within columns followed by the same letter 

 are not significantly different at odds of 19:1. 



10 



Fruit Notes, Summer, 1993 



