Structural Refinement of Spheres for 

 Controlling Apple Maggot 



Starker Wright, Ronald Prokopy, and Xing Ping Hu 

 Department of Entomology, University of Massachusetts 



Currently, there is no clear indication of the 

 extent to which organophosphate insecticides will 

 continue to be labeled for use in commercial apple 

 production. If recent state and federal decision- 

 making trends can be used as a guide for future 

 action, then we should prepare ourselves for the 

 possibility that the pre-harvest interval for orga- 

 nophosphate insecticides (particularly 

 azinphosmethyl) may be lengthened considerably, 

 possibly to 60 days or more. The purpose for do- 

 ing this would be to eliminate all detectable resi- 

 due on fruit at harvest, a principal aim of the Food 

 Quality Protection Act (FQPA). This same sce- 

 nario could well apply to permissible use patterns 

 of carbamate insecticides, the only other class of 

 labeled materials known to be at least moderately 

 effective against apple maggot. 



For many years (as reported in Fruit Notes), 

 we have conducted studies aimed at development 

 of behavioral control of apple maggot using traps 

 as a substitute for insecticide applications. These 

 studies have led to the development of pesticide- 

 treated spheres as a potential alternative in com- 

 mercial apple production. Such spheres are in- 

 tended to be inexpensive, easy to use, safe to handle, 

 and to offer reliable control of apple maggot. 



In 1997, we began an extensive comparison of 

 odor-baited sticky coated spheres, pesticide-treated 

 wooden spheres, and biodegradable pesticide- 

 treated spheres for direct control of apple maggot 

 flies (AMF) in commercial orchards. This study 

 was conducted in eight commercial apple orchards, 

 each containing four blocks of 49 trees each. In 

 each orchard, one block received three insecticide 

 sprays for AMF control, one block was surrounded 

 by sticky-coated wooden spheres, one block was 

 surrounded by pesticide-treated wooden spheres, 

 and one block was surrounded by biodegradable 

 pesticide-treated spheres. The results [Fruit Notes 



62(4)] showed that pesticide-treated biodegradable 

 spheres performed as well as sticky spheres and 

 considerably better than pesticide-treated wooden 

 spheres on which we were unable to preserve an 

 effective level of feeding stimulant. None of the 

 three trap types provided quite the level of AMF 

 control as 3 insecticide sprays did. In the case of 

 biodegradable pesticide-treated spheres, compro- 

 mising factors were that some spheres cracked pre- 

 maturely, some were eaten by birds and/or rodents, 

 and some were overgrown by fungi, reducing the 

 number of effective spheres comprising the barrier 

 to fly immigration into some blocks. Despite short- 

 comings, our 1997 findings were encouraging, as 

 all sphere types performed well under high pest 

 pressure in commercial orchards. 



Our goal for 1998 was to conduct experiments 

 leading to improved versions of pesticide-treated 

 spheres and to evaluate these for direct control of 

 AMF. Here we report on structural refinements of 

 both pesticide-treated biodegradable spheres and 

 pesticide-treated wooden spheres. 



Materials & Methods 



To maximize effectiveness and durability of bio- 

 degradable spheres, we addressed each of the short- 

 comings of such spheres experienced in 1997: 



1 ) To combat premature breakdown of biodegrad- 

 able sphere bodies, we evaluated seven differ- 

 ent structural compositions. We assessed each 

 body type for drying ti-ne, hardness, and resis- 

 tance to humidity. 



2) To ease deployment, we replaced the trouble- 

 some string hangers with wire hooks, and used 

 a metal disc beneath each sphere to support 

 the weight of the sphere body. 



3) To prevent consumption of spheres by rodents, 



Fruit Notes, Volume 63 (Number 4), Fall, 1998 



