Tests of Imidacloprid-treated Spheres 

 for Controlling Apple Maggot Fly 



Starker Wright, Xing Ping Hu, and Ronald Prokopy 

 Department of Entomology, University of Massachusetts 



In the 1996 and 1997 Spring issues oi Fruit 

 Notes, we reported on studies aimed at devel- 

 opment of pesticide-treated spheres (PTS) as a 

 substitute for sticky spheres for direct control 

 of apple maggot flies. In concept, a PTS would 

 be coated with a mixture of insecticide, fly feed- 

 ing stimulant, and residue-extending agent. A 

 fly landing on such a sphere would feed, ingest 

 insecticide, and die before laying any eggs. The 

 need to use labor-intensive sticky substances 

 (such as Tangletrap) to capture alighting flies 

 would be eliminated. Several earlier trials in- 

 dicated that dimethoate was the most effective 

 among orchard-labeled insecticides for use on 

 spheres, but its high human toxicity poses too 

 great a risk to the handler. In 1996, we found 

 that the newly-labeled insecticide imidacloprid 

 was a safer alternative to dimethoate and was 

 seemingly as effective. 



Sucrose (table sugar) has proven to be, by 

 far, the most effective fly feeding stimulant. 

 However, while mixing with latex paint pre- 

 serves the residual activity of the insecticide, 

 all sugar is lost from the sphere surface follow- 

 ing rainfall. We have taken two separate ap- 

 proaches to preserving residual activity of su- 

 crose: (1) development of a method in which 

 the activity of sucrose is extended on reusable 

 wooden spheres, which are annually coated with 

 a mixture of sucrose, insecticide, and latex paint; 

 and (2) development of a method in which the 

 entire sphere body is constructed of a mixture 

 of sucrose, flour, and glycerin, coated with a mix- 

 ture of insecticide and latex paint so as to cre- 

 ate a biodegradable sphere. Here we report on 

 two experiments leading to refinement of resi- 

 due-extending agent, fly-killing agent, and 

 evaluation of each sphere type for direct con- 

 trol of apple maggot flies in commercial or- 

 chards. 



Materials & Methods 



In our first experiment, we evaluated in 

 laboratory studies three formulations of 

 imidacloprid (EC, WP, technical grade) in com- 

 bination with each of three formulations (flat, 

 semi-gloss, gloss) of each of four commercial 

 brands of red latex paint (36 treatments in all). 

 We found the EC and WP formulations of 

 imidacloprid in Glidden Red Latex Gloss 

 Enamel paint to be the most promising. We then 

 placed wooden spheres coated with two concen- 

 trations of each formulation of imidacloprid in 

 orchard trees and evaluated them for their abil- 

 ity to kill apple maggot flies at 0, 3, 6, 9, and 12 

 weeks after placement. 



In our second experiment, two sphere types 

 were assessed in an attempt to extend the re- 

 sidual activity of sucrose on the sphere surface. 

 Each wooden PTS was fitted with a 3-cm-di- 

 ameter ring of specially formulated caramelized 

 sucrose around the hook at the top of the sphere. 

 The sucrose spread down the sides of the sphere 

 after each rainfall, continually replenishing the 

 sugar supply on the sphere surface. This type 

 of sphere was developed as a replacement for 

 spheres tested in 1996 in which holes were 

 drilled and filled with sucrose prior to paint- 

 ing, as described in the Spring 1997 issue of 

 Fruit Notes. Further testing of the 'spheres with 

 holes' revealed that construction was far too 

 costly and time consuming to be of practical 

 value. For sugar/flour biodegradable spheres, 

 the following composition of ingredients proved 

 best: sucrose/fructose syrup (25%), 

 pregelatinized corn flour (25%), wheat flour 

 (25%), glycerin (10%), and water (15%). After 

 hardening in the laboratory, such spheres emit 

 a continuous supply of sugar to the surface, ir- 

 respective of rainfall amount. 



Fruit Notes, Volume 62 (Number 4), Fall, 1997 



