FQPA-related Pesticide Residue 

 Study, 1 999 



William M. Coli,Jolin M. Clark, Raymond Putnam, Sibilla Zak, and Saida Safiyeva 

 Department of Entomology, University of Massachusetts 



Over the past several years, Members of the UMass Fruit 

 Team have endeavored to provide information to Massa- 

 chusetts fruit, vegetable, and berry growers as well as other 

 pesticide applicators on developments associated with imple- 

 mentation of the Food Quality Protection Act of 1996 

 (FQPA). For fruit growers, this role has taken the form of 

 multiple slide presentations at twilight meetings and annual 

 updates in the March Message to Massachusetts fruit grow- 

 ers. These activities have also benefitted from close coop- 

 eration with Glenn Morin and Robin Spitko (NEFCON) who 

 have been closely involved tlirough membership on the na- 

 tional Tolerance Reassessment Advisory Committee (TRAC) 

 and the National Alliance of Independent Crop Consultants. 



In 1999, at the request of leading Massachusetts fruit 

 growers, the Fruit Team designed two studies to generate 

 data on mitigating uses of the key organophosphate (OP) 

 insecticides azinphosmethyl and phosmet for submission to 

 EPA. The studies were conducted at nine commercial fruit 

 farms in Massachusetts and two in New Hampshire. Pesti- 

 cide residue analyses were conducted by the Massachusetts 

 Pesticide Analytical lab (MPAL) at UMass, Amherst. Stud- 

 ies were designed to show the effects on residues at harvest 

 of restricting azinphosmethyl use only to the early season 

 against plum curculio (Residue Decline Study), or of using 

 various rates (full rate, half rate, one quarter rate) of 

 azinphosmethyl or phosmet later in the season against apple 

 maggot (Bridging Study). A residue-decline study seeks to 

 establish a relationship between residue levels at the time of 

 application and those detected over time, including at the 

 pre-harvest interval specified on the label. A bridging study 

 is intended to establish a relationship among residues from 

 field trials conducted at the maximum application scenario 

 (e.g., maximum application rate, highest application fre- 

 quency, and shortest pre-harvest interval) and residues which 

 occur from more typical applications. 



Materials & Methods 



Treatments. Seven orchards agreed to participate in 

 the Azinphosmethyl Residue Decline Study (ARDS). Each 

 test block consisted primarily of well-pruned, mature, semi- 

 dwarf Mcintosh trees. Applications were conducted by co- 

 operating growers using their own calibrated sprayers and 



the 50WSP fonnulation, at per-acre rates ranging from 0.75 

 to 1.5 lbs. fomiulated product per acre (depending on tree 

 row-volume). Timing and need for applications were deter- 

 mined by the grower, but no azinphosmethyl applications 

 were planned after the last spray for plum curculio. Fungi- 

 cides were applied by the grower on an as-needed basis and 

 were not part of the residue analysis. 



Three orchards agreed to participate in the Phosmet 

 Bridging Study (PBS). Each test block consisted primarily 

 of well-pruned mature Mcintosh trees. With the understand- 

 ing that one grower planned to switch from early-season 

 azinphosmethyl use to later-season use of phosmet, in that 

 case, the PBS was overlain on trees also sampled for the 

 ARDS. In the other two orchards, phosmet was the insecti- 

 cide primarily used tliroughout the season, so no ARDS was 

 conducted. Pesticide applications were conducted by coop- 

 erating growers using their own calibrated sprayers and ei- 

 ther the 70WP or 70WSB fonnulation, at per acre rates rang- 

 ing from 0.8 to 3 lbs. fomiulated product per acre (depend- 

 ing on tree-row volume). Timing and need for applications 

 were once again determined by the grower, and fungicides 

 were applied as needed. 



At the request of the growers, one orchard was the site 

 of an Azinphosmethyl Bridging Study (ABS), using three 

 rates of the 50 WSP formulation: 10 oz., 5 oz., and 2.5 oz. 

 per 100 gallons, and a second was the site of an ABS using 

 two rates of the 50 WSP fonmilation: S oz. and 4 oz. per 

 100 gallons. Cultivar mix and tree size in these two blocks 

 were the same as other blocks described above. Timing and 

 need for applications were once again determined by the 

 grower, and fiingicides were applied as needed. 



Sample collection. At the study's onset, the authors 

 met to discuss the protocol for collectmg and storing sanples. 

 It was decided initially to collect composite samples of up 

 to 20 fruit (depending on size) from each treatment block in 

 collaborating orchards approximately monthly through the 

 season. Fruit were collected by snipping the stem with a 

 hand pruners (so as to not contaminate individual fruit by 

 handling) and dropping the fruit into previously-labeled foil- 

 lined Zip-Loc'^'^ bags. Once fruit were collected, bags were 

 placed immediately into a cooler with ice packs and returned 

 to campus. After recording the specimens into a chain of 

 custody form at the MPAL, samples were frozen and stored 



50 



Fruit Notes, Volume 65, 2000 



