Do Sugar Caps Atop Wooden 

 Pesticide-treated Spheres Affect Apple 

 Maggot Fly Attraction to Spheres? 



Gerald Lafleur, Juan Rull, and Ronald Prokopy 

 Department of Entomology, University of Massachusetts 



In three preceding articles in this issue of Fruit 

 Notes, we have shown that wooden or plastic pesticide- 

 treated spheres (PTS) topped by sugar/wax discs that 

 release a continual supply of sugar onto the sphere 

 surface hold much promise for directly controlling 

 apple maggot flies (AMF). More specifically, we found 

 that discs of 2-inches diameter x %-inch height 

 (weighing 50 grams) contain and release enough sugar 

 to endure up to about 6 inches of rainfall and/or 6 weeks 

 of orchard exposure before the supply of sugar is spent. 

 Ideally, to be cost-effective and appealing to growers 

 for use in controlling AMF, discs ought to contain 

 enough sugar to supply a sphere for the entire 1 2 weeks 

 of the AMF season and do so under 12 inches or more 

 of rainfall. This can be accomplished by increasing 

 the size of the disc to some upper limit beyond which 

 the shape of a sphere is sufficiently altered so as to 

 become less attractive to AMF. 



Here, we report results of a field test conducted in 

 2001 evaluating the impact on attractiveness to AMF 

 of different sizes of discs atop plastic PTS. 



Materials & Methods 



All spheres were 3.5 inches in diameter, red in 

 color, made of durable plastic and purchased from Great 

 Lakes IPM of Vestaburg, Michigan. All discs were 

 cut out from pink styrofoam insulation panels. The 

 pink color of these discs was equivalent to initially red 

 sugar/wax top caps that had lost about one-third of their 

 sugar content under about 2 inches of rainfall. The 

 size of discs ranged from 1 .5-inches diameter x y4-inch 

 tall to 3-inches diameter x 1. 5-inches tall. All discs 

 were centered atop plastic PTS (Figure 1). The entire 

 surface of each sphere (but not the disc) was coated 

 with Tangletrap to capture alighting AMF. 



Spheres were hung from branches of fruiting 



Delicious trees (M.26 rootstock) in an unsprayed block 

 of apple trees at the Horticultural Research Center in 

 Belchertown on July 3 1 . Each of the 72 fruiting trees 

 contained a single sphere. For each replicate, there were 

 nine treatments consisting of eight sizes of discs plus 

 a control sphere without any disc. Each of these nine 



(a) 



(b) 



Figure 1. Schematic illustration of a 3.5-inch 

 sphere topped by a disc of (a) 1. 5-inches diameter 

 X Vinch tall or (b) 3-inches diameter x 1. 5-inches 

 tall. 



Fruit Notes, Volume 66, 2001 



37 



