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benlate"^ residues on red delicious 



R. Kammereck 



Consultant 



and 



R.D. Bartram 



Tree Fruit Research Commission 



Washington State 



in order to prolong storage life and reduce fungus-caused decay, Red 

 Delicious apples are routinely treated with Benlate by some packinghouses. 

 This treatment is made after harvest and during the preparatory stages 

 preceding packaging. Most countries place strict limitations on the quan- 

 tity of fungicide (residue) remaining in fruit at the time of purchase by 

 the consumer. It is, therefore, of great interest to fruit sales organiza- 

 tions to have a clear understanding of the level of residue at the time of 

 sale. 



Residue Study 



The following results and conclusions were obtained from an analysis of 

 data derived from the chemical determination of benomyl and its metabolic 

 breakdown product MBC in Red Delicious apples treated commercially with the 

 fungicide Benlate^. This study was designed to explore the fate of benomyl 

 (the active ingredient of Benlate^) as influenced by 1) application condi- 

 tions, 2) storage time and storage facilities, and 3) treatment of fruit 

 prior to packaging. The chemical determinations were performed at the USOA 

 Yakima Agricultural Research Laboratory by Research Chemist Don George in 

 IBS'* and I985 on preceding year fruit samples. 



During the course of the chemical extraction procedure, all benomyl was 

 altered to MBC and measured in the MBC form. In the following report, the 

 term "benomyl equivalent" stands for combined benomyl and MBC present in 

 whole fruit samples at time of chemical analysis, and its concentration is 

 expressed as milligrams per kilogram of fresh fruit (ppm). Data were sub- 

 jected to statistical analysis. 



Benlate^ Drenches, I983 



In the 1983 trial, apples were drenched with Benlate^ at commercially 

 recommended rates. Fruit, prior to storage, contained benomyl -equ ivalent 

 residues of 0.85 ppm on the average, with residue levels ranging from 0.49 

 to 1 .'♦2 ppm. The odds against finding apple sample lots with average resi- 

 due levels of greater than 0.93 Ppm were more than 1000 to 1. 



During subsequent storage of these fruit under "cold room" conditions 

 for up to 180 days, there was no statistically significant change in the 

 average residue level. Similarly, storage for I8O days under "controlled 

 atmosphere" conditions had no effect on the average residue concentration. 



BenlateT< Drenches, 1984 



In 1984 when this trial was repeated under comparable procedures, the 

 average level of benomyl equivalent prior to storage increased to 1.41 ppm. 

 The reasons for the observed increase cannot be deduced from the data given, 

 but likely causes are differences in BenlateTl solution concentration, dura- 



