ses. (The other half was retained at Veryfine for 

 daminozide residue analysis as part of the overall 

 study.) 



Amounts and dates of pesticide application were 

 obtained from growers, as well as information on vari- 

 ous tree and block characteristics. Data analysis was 

 done at the University of Massachusetts. The key 

 factors we examined were the number of applications, 

 the interval between the last application and harvest, 

 the amount of EBDC formulation applied per acre over 

 the season, the number of applications made and the 

 amount of fungicide applied after the last significant 

 rain of the season in July, and the amount of captan ap- 

 plied relative to the amount of EBDCs. 



Of the 28 blocks tested, 10 had EBDC residues 

 which were detected. Of these, 1 had received 4 appli- 

 cations of an EBDC, 1 had received 6 applications, and 

 the rest had received 7 or more. Of the blocks with non- 

 detected residues, all had received 8 or less EBDC 

 applications over the season (Figure 1). Thus, we esti- 

 mated a "break-point," or point where residues built 

 up sufficiently to be detected in 9 of 10 cases, at 6 

 applications. The EBDC residues and the numbers of 

 applications for the season were well related ( r = 0.69; 

 the correlation coefficient, r, is a statistic which ranges 

 between -land + l.indicatingthe degree of correlation, 

 with meaning no correlation and + 1 or -1 meaning 

 perfect correlation). 



We next examined the effect that the total amount 



of EBDC fungicides applied over the season had on the 

 measured residue (Figure 2). Of course, the total 

 amount of fungicide applied over a season increased as 

 the number of applications per season increased (r = 

 0.95). As would be expected, the more fungicide ap- 

 plied, the more residue detected (r = 0.66). The 

 apparent "break point" was at about 15 pounds/acre/ 

 season. 



One might also expect that the number of days 

 between the last EBDC application and harvest would 

 affect residues. While there was a moderate correla- 

 tion, the relationship was not as strong (r = -0.33) as 

 that observed with some of the other factors (Figure 3). 



We also considered that significant rain which 

 occurred in July may have removed residue approxi- 

 mately 60 to 70 days before harvest. During the 10 days 

 prior to July 23, over 8 inches of rain fell in many areas. 

 Therefore we examined the number of applications 

 and the pounds of EBDC applied after the July 23 rain. 

 Of the 13 blocks which received applications of EBDC 

 after July 23, 8 blocks had detected residue, and 5 did 

 not (Figure 4). All blocks that received 2 applications 

 after July 23 had detected residues, indicating that late 

 applications were related to residue (r = 0.64). The 

 pounds per acre applied after July 23 were more closely 

 related (r = 0.78), and more fungicide was applied after 

 July 23 in 8 of the 10 blocks with detected residues than 

 in the blocks with no detected residues (Figure 5). 



We also examined the amounts of captan relative 



Lbs./Acre Applied 

 Over the Season 

 60 



50 



40 



30 



20 



1 







9 11 13 15 

 Orchard Block 



17 19 21 23 25 27 



Figure 2. The pounds of EBDC fungicide used per acre for the 1988 season, compared with the EBDC 

 residue on apple samples. Where detectable, the amount of residue increases from left to right; blocks 

 which had no detected residues are represented in the white background, and blocks with a detected 

 residue are in the shaded background. 



Fruit Notes, Winter, 1990 



23 



