16 



tion of use of drench baths, quantity of fruit treated, etc. The variation 

 in residue levels among treated fruit can be expressed as the 1000 to 1 odds 

 against detection in apple sample lots of average residue levels greater 

 than 1 .49 ppm. 



"Cold room" storage again did not affect the benomyl residues dif- 

 ferently than "controlled atmosphere" storage, but there was a substantial 

 lowering of residue levels in both storage conditions. After 180 days the 

 residue concentration declined on average by 22^ 



Effective Control 



In both years, apples involved in the drench treatment trials would 

 have been likely to pass inspection in all those countries imposing a 2.0 

 ppm tolerance on residue concentration. But the achieved benomyl level in 

 1983 must be considered too low for effective decay control. 



Benlate"^ with Wax, 1983 



Extending the "drench and store" treatment experiment to an additional 

 mode of fungicide application. Red Delicious apples in I983 and 198't were 

 treated with Benlate^ in combination with wax. in the I983 trial, stored 

 fruit pretreated by drenching and exhibiting a benomyl -equ ivalent level of 

 0.35 ppm average was sprayed prior to packaging with a Benlate^-wax mixture, 

 then stored for 60 days. 



After waxing, the benomyl levels were raised substantially to an 

 average of 1.33 ppm. At this stage the variability of residue concentration 

 among individual fruit was such that if a random sampling of apples were done 

 then the odds against finding a sample lot with an average residue level of 

 1.^2 ppm or greater were 1000 to 1 . As was observed in the ^SB^ "drench and 

 store" trial (but not in the corresponding I983 trial), the benomyl levels 

 decreased significantly during storage at a rate of about 20% in 60 days. 



Benlate"^ with Wax, 198't 



This experiment was repeated in 198'* at another warehouse. Starting from 

 an average benomyl concentration of 0.36 ppm, spray application combined with 

 waxing raised the average benomyl equivalent level to 2.89 ppm. Variability 

 in residue concentrations among fruit was such that had a random sampling of 

 apples been done just after waxing, then 1 out of 10 sample lots would have 

 shown average benomyl equivalent levels of at least 3.0 ppm. During storage 

 over a period of 60 days the average level of benomyl decreased by about 19?. 

 This rate of loss would bring a typical fruit lot into compliance with a 2.0 

 ppm tolerance limitation after an estimated 105 days of storage. 



Effect of Packingline Practices 



A further test in 198^* sought to determine the influence of packing 

 line operations such as grading, sorting and washing on fungicide levels. 

 Grading and sorting operations had no significant effect on the residue 

 levels. But washing prior to waxing reduced the residues on the average by 

 2'*%. Waxing increased residues substantially, although the test protocol 

 does not mention the addition of Benlate^ to the waxing spray in this par- 

 ticular experiment. 



