Absorption and Metabolism of Dimethoate In the Bollworm and Boll Weevil1

Abstract

P³²-labeled dimethoate was absorbed and excreted rapidly by fifth-instar bollworm larvae (Heliothis zea (Boddie)) and adult boll weevils (Anthonomus grandis Boheman). These insects absorbed 54.2% and 74.5% of topically applied dimethoate, respectively, after 24 hours and 76.2% of an injected dose of dimethoate was excreted by bollworm larvae after 24 hours. The in viro metabolism of P³²-labeled dimethoate in adult boll weevils, fifth-instar bollworm larvae, and cotton seedlings was characterized qualitatively and quantitatively though the use of paper chromatography, autoradiography, and standard radio assay procedures. Dimethoate and 11 metabolites were detected in various insect and plant extracts. In bollworms, the principal initial sites for hydrolytic cleavage of the dimethoate molecule were the carbonyl-nitrogen bond and the sulfur-carbon bond The oxygen analog of dimethoate was formed in both plants and insects but was broken down rapidly by the latter to nontoxic products.