The fate of some organochlorine pesticides on leaves

Abstract Apple trees were sprayed with commercial formulations of the organochlorine pesticides aldrin, endrin, dieldrin, endosulfan, gamma‐BHC, DDT and TDE. Samples of leaves were taken at approximately fortnightly intervals up to three months and examined for the presence of both the unchanged pesticides and their conversion products. Deposits resulting from the application of emulsifiable concentrates were more persistent than those from the same pesticides applied as dispersible powders. The dieldrin and DDT emulsifiable concentrates gave the most persistent deposits, residues taking eleven weeks to fall to below 5% of the initial deposits. Only aldrin, dieldrin and endosulfan gave significant amounts of ultraviolet irradiation products. Details are given of the experimental work undertaken on the characterisation of two previously unknown conversion products, both of which are of similar toxicity to, but more persistent than their respective parent compounds.