mixed at 5% with sphere body ingredients. Sub- 

 sequent lab and field tests indicated that AMF were 

 completely unaffected by the pepper additive, 

 whereas damage to spheres by rodents was greatly 

 reduced or eliminated. Field assays revealed that 

 bird damage to biodegradable spheres was substan- 

 tially reduced by painting spheres black, thus mak- 

 ing them less visually attractive to foraging birds. 

 Fortunately, AMF are equally attracted to black 

 and red spheres. Given this early-season progress, 

 we were confident in the potential of biodegrad- 

 able pesticide-treated spheres to offer AMF con- 

 trol comparable to sticky-coated wooden spheres. 

 Data trends established in the 1997 comparison of 

 sphere types held true in 1998. Results for 1998 

 (Table 1) showed that biodegradable pesticide- 

 treated spheres performed about as well as sticky 

 spheres (0.77% and 0.70% injured fruit, respec- 

 tively) and nearly as well as three insecticide appli- 

 cations (0.59% injured fruit). As in 1997, wooden 

 pesticide-treated spheres released the entire sucrose 

 supply too quickly, and did not perform as well 

 (2.93% injured fruit). Unfortunately, many bio- 

 degradable spheres required replacement after 

 about a month of field exposure due to softening 

 and bursting of the sphere bodies. 



Conclusions 



Pest pressure in commercial orchards in 1998 

 was even higher than in 1997 (an average of 1702 

 AMF per block captured by the 26 sticky spheres 

 per block). Despite shortcomings of biodegrad- 

 able and wooden pesticide-treated spheres, we are 

 nonetheless encouraged by the 1998 results, par- 



ticularly by the performance of biodegradable 

 spheres under very high pest pressure. With fur- 

 ther structural modifications and pending commer- 

 cial production of biodegradable sphere bodies, we 

 are becoming increasingly confident in recommend- 

 ing use of sphere traps in place of insecticide sprays 

 for control of AMF in commercial orchards. As 

 discussed m the Introduction, development of al- 

 ternatives for control of AMF is gaining emphasis 

 given the implications of FQPA implementation. 



For the 1999 field season, we will again com- 

 pare the efficacy of sticky-coated wooden spheres, 

 pesticide-treated wooden spheres, and pesticide- 

 treated biodegradable spheres for direct control of 

 AMF. In 1999 field trials, pesticide-treated wooden 

 spheres will be augmented with a new sucrose-re- 

 lease mechanism, and biodegradable spheres used 

 in 1999 will be commercially-made prototypes, 

 produced by a private corporation under USDA 

 supervision. 



Acknowledgments 



This work was supported by state/federal IPM 

 funds, a grant from the Washington Tree Fruit Re- 

 search Commission, a USDA SEA CSREES grant 

 (# 97-34365-5043), and a SARE grant (USDA 96- 

 COOP-1-2700). As always, we are grateful to the 

 seven growers who participated in this study: Bill 

 Broderick, Dana Clark, Dave Chandler, Tony Lin- 

 coln, Wayne Rice, Dave Shearer, and Tim Smith; 

 and to our field technicians: Jon Black, Joel Benton, 

 Anthony Minalga, Stephen Lavallee, Eric 

 Gemborys, and Max Prokopy. 



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



