tion of samples immediately after application. 



Sample extraction and analysis. Azmphosmethyl and 

 phosmet residues were analyzed as reported previously (S. 

 Wright, et al., 1998, Fruit Notes 63(2): 1-3). Residues were 

 analyzed from extracted whole apples using gas clrromatog- 

 raphy with nitrogen-phosphorus and Mass-selective detec- 

 tion. Pesticide recoveries from organic apples fortified with 

 azinphosmethyl and phosmet (0.05 Fg/g - 2.0 Fg/g, N=38) 

 were 98.5 % ± 15 and 105 ± 16, respectively. Residues of 

 azinphosmethyl and phosmet were never detected on any 

 (N=38) of the laboratory control samples (organic apples). 



Residue Decline Study Results and Discussion 



Not surprisingly, residues of azinphosmethyl were de- 

 tected on samples collected approximately one month after 

 the last actual application in all seven treatment blocks (Table 

 1). However, largely in keeping with our original hypoth- 

 esis, there were no detectable azinphosmethyl residues (limit 

 of detection = 0.04 Fg/g) on any fruit collected 14 days prior 

 to harvest in six out of seven sampled ARDS blocks. This 

 result was consistent with a study conducted by Wright et al. 

 in 1997 {Fruit Notes Vol. 63 (2): 1-3, 1998.) where they 

 found no detectable residues at harvest in five third-level 

 1PM blocks which received no azinphosmethyl applications 

 after June 30. 



In one orchard, small amounts of azinphosmethyl were 

 detected prior to harvest (0.12 and 0.1 1 Fg/g respectively), 

 in two out often composite samples taken. This was in spite 

 of the fact that no Azinphosmethyl was detected on samples 



taken on three previous dates in that block. We are unable 

 to explain fully the presence of these residues, since the 

 grower assures us that no azinphosmethyl had been applied 

 to the block or anywhere else in the entire orchard after May 

 27. We suspect that results reflected the extremely dry sum- 

 mer experienced in Massachusetts in 1999. Presence of small 

 residues in two out of nine pooled samples collected on 9/7 

 reaffirms the need for multiple samples in order to account 

 for residue variation among individual fruits growing on 

 different trees or at different positions on trees. 



Bridging Study Results and Discussion 



In the three orchards which participated in the phosmet 

 bridging study, there appeared to be a trend toward correla- 

 tion between rates applied and resultant residues (Table 2). 

 In one PBS block, azinphosmethyl residues just above the 

 analytical limit of detection (data not shown) were found at 

 the PHI in trees which the grower reports had received no 

 deliberate applications of that material. Based on the 

 grower's spray records, we suspect that this may have been 

 due to drift from adjacent blocks of trees that received a late 

 season application of a low rate of azinphosmethyl against 

 apple maggot fly. 



In the two orchards which conducted the azinphosmethyl 

 bridging study, there was a much better relationship between 

 rates used and resultant residues (Table 3). The differences 

 can not be explained conclusively, although variation in 

 mixing/loading procedures, weather during application, or 

 sprayer calibration likely contributed. 



52 



Fruit Notes, Volume 65, 2000 



