| Abstract: | Four experiments using the insecticides malathion and chlorpyrifos on mature, unharvested and harvested sultana grapes provided information on the efficiency of application and the rate of loss of insecticides, through the phases of preharvest to processing. Unharvested bunches retained 3.5-8.1% of the active ingredient (a. i.), whereas harvested bunches laid out to dry retained 23% a. i. Insecticide decay was greatest immediately after application, probably due to volatilisation of unbound chemical, but the rate of loss was accelerated by the use of alkaline drying oils which stimulated hydrolytic degradation. Drying oils are conventionally applied to hasten drying. The residue on fruit at the end of drying was generally higher than that on the fresh fruit because of the concentration effect of dehydration. Processing and storage did not alter the residues, probably because the chemical migrated into the fruit and became bound to inert compounds. |
