Buildup of Bugs Causes Decline in 

 Effectiveness of Sticky for 

 Capturing Apple Maggot Flies 

 on Red Sphere Traps 



Jian Jiin Duan, Xingping Hu, Max P. Prokopy, and Ronald J. Prokopy 

 Department of Entomology, University of Massachusetts 



Red spheres coated with sticky 

 (TangletrapTM) have been used for 25 years as 

 effective traps for monitoring apple maggot fly 

 abundance in commercial orchards. Once sticky 

 spheres have been emplaced, a treatment of 

 pesticide is recommended when cumulative cap- 

 tures of maggot flies reach one or two per 

 unbaited trap or five per trap baited with syn- 

 thetic apple odor (butyl hexanoate). We and 

 others have long suspected that buildup of in- 

 sects and debris on the sphere surface might 

 cause a progressive decrease in the probability 

 of capturing an ahghting maggot fly. In 1993, 

 we evaluated the rate of decline in the power of 

 traps to capture maggot flies. 



On Jiuie 28, we hung 24 freshly-coated 

 sticky red spheres in optimum positions on 

 apple trees in a commercial orchard. Each 

 sphere was baited with one vial of butyl 

 hexanoate and one packet of ammonium ac- 

 etate in a manner typical for spheres used in 

 trapping apple maggot flies in second-level IPM 

 blocks. Eight freshly-coated spheres were placed 

 in a cardboard box in a closet at 70°F as checks. 

 After 7, 14, and 28 days, eight spheres on each 

 date were removed from the orchard and like- 

 wise placed in cardboard boxes in the closet. In 

 early August, spheres of each treatment were 

 hung in potted apple trees in field cages to test 

 their fly capturing power. Ten flies were re- 

 leased toward the bottom of the tree canopy, 

 which contained a single sphere. The sphere 

 was observed continuously for one hour, after 

 which all flies were removed from the cage. We 

 recorded the number of flies alighting, the num- 



ber captured, and the number that escaped. We 

 also estimated the percent of the surface area 

 occupied by captured insects. Once a trial 

 ended, we hung up a sphere of the next treat- 

 ment and released 10 more flies. We did this 

 until all 32 spheres were tested. 



As time of sphere exp>osure in commercial 

 orchard trees increased fi-om to 28 days, the 

 proportion of released flies caught decreased 

 significantly firom 49% to 13% (Figure lA). 

 There was no significant effect of time of sphere 

 exposure in commercial orchards on propensity 

 of flies to alight on spheres (Figure IB). Of the 

 ahghting flies, only 3% escaped from spheres 

 kept continuously in the closet (never emplaced 

 in commercial orchards) compared with 38, 43, 

 and 73% escapees fi-om spheres exposed in or- 

 chards for 7, 14, and 28 days, respectively 

 (Figure IC). As days of exposure in orchard 

 trees increased, the percentage of sphere sur- 

 face area occupied by captured insects increased 

 significantly from to 16, 24, and 38% afler 7, 

 14, and 28 days of exposure, respectively (Fig- 

 ure ID). 



We conclude from this test that sticky red 

 spheres become progressively less effective in 

 capturing alighting apple maggot flies as the 

 number of insects caught on the spheres in- 

 creases over time. It appears that under com- 

 mercial orchard conditions, odor-baited sticky 

 spheres lose nearly half of their maggot fly 

 capturing power after two weeks without clean- 

 ing. After four weeks without cleaning, they 

 lose about three-fourths of their maggot fly 

 capturing power. We therefore recommend 



8 



Fru'n Nates, Spring, 1994 



