Conclusion 



Based on these results, it appears that our original hy- 

 pothesis (that restricting azinphosmethyl appHcations only 

 to early-season pests) typically will result in no detectable 

 residues at harvest. Such a potential strategy is essentially 

 the same as increasing the PHI to 90 days, far more than the 

 current requirement of 14 to 21 days (depending on rate of 

 last application). Given the extremely low rainfall during 

 the 1999 growing season, this test can be considered to be a 

 "worst-case scenario," given that weathering by rainfall is a 

 significant source of residue removal from fruit under more 

 normal conditions. Results also point out the substantial 

 variability of application outcomes from orchard to orchard. 

 This variability likely results not only from use of different 

 sprayers, travel speeds, rates of concentration (e.g., 3X, 6X, 

 etc.), and frequency of calibration, but also from individual 

 grower's mixing/loading and application style. 



Regarding use of lower-than-maximum label rates, our 

 data confirm that residues of azinphosmethyl at harvest, 



while affected by the date of last insecticide application, are 

 also related to rate of formulated product used. Thus, using 

 the lowest effective rates not only makes good economic 

 sense, but also provides an additional margin of safety re- 

 garding potential residues at harvest. Such a low-dose strat- 

 egy also can be a resistance-management tool given that pest 

 resistance typically develops to the highest rate to which 

 pests have been exposed. 



A ckn a wledgm en ts 



We sincerely thank all cooperating growers: Gerard 

 Bierne, Bill Broderick, Greg Gilmore, Rick Leadbeater, Jay 

 Marshall, Andrew Martin, Bill Rose, Max Russell, Joe 

 Sincuk, Mo Tougas, and Steve Wood. This study was paid 

 for with contributions from some cooperating growers, and 

 with funds from the Massachusetts Pesticide Impact Assess- 

 ment Program, and the UMass Agroecology Tree Fruit 

 Smith-Lever Extension budget. 



it it it it it 



Fruit Notes, Volume 65, 2000 



53 



