Pesticide residues and metal contents in flue-cured tobacco leaf, Ontario, 1986-88
Between 1986 and 1988, 30 Ontario farms growing flue-cured tobacco (Nicotiana tabacum L.) were surveyed for their annual pesticide applications, and their cured tobacco crops were sampled for analysis of pesticide residues and toxic metals. The use surveys showed that applications of synthetic pyrethroids for cutworm control increased while those with chlorpyrifos decreased from an earlier survey. Acephate was the most widely used insecticide for foliar insects and was followed by deltamethrin and permethrin. Analysis of cured tobacco leaf revealed no detectable synthetic pyrethroid insecticide residues. Diphenamid residues appeared in cured leaf where it had been applied for weed control, however the residue was mainly the N-methyl metabolite, N-methyl 2,2-diphenylacetamide. Minor residues of several organochlorine insecticides were still to be found in cured leaf 10 to 20 years after their use had been terminated. Organophosphorus insecticide residues were absent or at trace levels in cured leaf except for acephate. Acephate residues were found where the insecticide had been used; however, these residues were present primarily as the methamidophos metabolite and were found at all stalk positions with the higher levels in sand leaves.