Commercial Orchard Trials of 

 Attracticidal Spheres for Controlling 

 Apple Maggot Flies 



Ronald Prokopy, Starker Wright, and Jonathan Black 

 Department of Entomology, University of Massachusetts 



For nearly a decade, we have been engaged in de- 

 velopment and refinement of pesticide-treated spheres 

 as a substitute for sticky-coated spheres for control- 

 ling apple maggot flies (AMF). This endeavor has 

 given rise to two rather different types of pesticide- 

 treated spheres. 



The first type consists of a wooden sphere coated 

 with a mixture of pesticide, latex paint (as a residue- 

 extending agent for pesticide), and sucrose (as a feed- 

 ing stimulant for alighting fiies). Because we have 

 been unable to find an effective residue-extending agent 

 for sucrose (which is washed away during rainfall), 

 we have taken an alternative route and attempted to 

 re -supply sucrose to the sphere surface through place- 

 ment of a cap of hardened sucrose on top of a sphere. 

 Ideally, sucrose would distribute gradually from the 

 cap onto the sphere surface during rainfall, leaving a 

 film of ample feeding stimulant after drying. 



The second type consists of a sphere whose body 

 is comprised of a mixture of moistened sugar, fiour, 

 and glycerin. After drying, this type of spheres looks 

 and feels as though it were a hardened ball of pie-dough. 

 Under rainfall, sugar seeps through the coat of latex 

 paint and pesticide applied to the sphere surface and 

 ideally provides a continuous supply of feeding stimu- 

 lant to the sphere surface. 



Here, for each of 3 years, we compared the effec- 

 tiveness of odor-baited pesticide-treated wooden 

 spheres and odor-baited pesticide-treated sugar/fiour 

 spheres with that of odor-baited sticky spheres or in- 

 secticide sprays for controlling AMF in commercial 

 orchards. 



Materials & Methods 



Tests were conducted in 1997, 1998, and 1999 in 

 each of eight commercial apple orchards in Massachu- 

 setts. Each orchard contained four blocks of medium- 



sized apple trees (M.26 rootstock) comprised almost 

 exclusively of the cultivars Mcintosh and Cortland. 

 Each block consisted of 49 trees in a seven x seven 

 arrangement: seven perimeter-row trees and six suc- 

 cessively internal rows of seven trees each. During 

 the first week of July each year (i.e., just before AMF 

 immigration), each of the 24 perimeter trees in three 

 blocks per orchard received an odor-baited sphere. All 

 spheres were red in color, 3 inches diameter, baited 

 with a polyethylene vial containing synthetic fruit odor 

 attractant (butyl hexanoate) and hung 2 to 3 yards above 

 the ground from apple tree branches in a way that maxi- 

 mized visual apparency and attractiveness. None of 

 the three blocks was treated with insecticide within 

 the 3 weeks prior to sphere deployment and none re- 

 ceived insecticide after sphere deployment. The fourth 

 block in each orchard was treated by the grower with 

 two or three sprays per year of azinphosmethyl or 

 phosmet to control AMF. 



For wooden spheres, the surface was treated once 

 with red gloss enamel paint and then after drying, was 

 overlaid with a mixture containing 70% of the same 

 paint, 20% sucrose, and 10% Provado (containing 20% 

 imidacloprid). Imidacloprid is just as toxic to apple 

 maggot flies and just as durable in latex paint as 

 dimethoate, the insecticide of choice for previous ver- 

 sions of pesticide -treated red spheres, and is safer than 

 dimethoate for handling of treated spheres. Painted 

 spheres were allowed to dry and then equipped with a 

 disc (0.75 inch tall x 1 .5 inches diameter) of caramel- 

 ized (hardened) sugar affixed to the top of each sphere 

 (Figure 1) In 1997, discs atop wooden spheres origi- 

 nated from a mixture of 61% sucrose, 17% fructose, 

 and 22% water, which, after heating to 150°C, was 

 poured into 0.75-by-l. 5-inch moulds and allowed to 

 cool and harden. It turned out, however, that such discs 

 dissipated in rainfall or dew more quickly than desired. 

 Therefore, in 1998, we used the same type of disc as in 



14 



Fruit Notes, Volume 64 (Number 4), Fall, 1999 



