RESIDUES OF CRONETON AND ITS SULFOXIDE AND SULFONE METABOLITES IN CITRUS (CLEMENTINE TREES) FOLLOWING A SOIL TREATMENT FOR THE CONTROL OF APHIS-SPIRAECOLA

Residues of the insecticide croneton, [2-(ethylthio)methyl]phenyl N-methylcarbamate, and its sulfoxide and sulfone metabolites were determined in Clementine (C. reticulata Blanco) leaves and fruits following soil treatment with 2, 6, and 18 g of active ingredient (AI) per tree. The analytical procedure was improved to separate croneton from its two oxygen analogues. Croneton was extracted with petroleum ether and its sulfoxide and sulfone metabolites with chloroform; all were silylated with bis(trimethylsilyl)trifluoroacetamide and determined by gas-liquid chromatography using the flame photometric detector. The carbamate was found to accumulate in the leaves and mainly in its oxidized forms. Soil treatment with 18 g of AI/tree resulted in a slow accumulation in the leaves during the first 12 days (up to 2 ppm), followed by a much faster rate. After 42 days the total residue level was 12 ppm (0.4 ppm croneton, 5.6 ppm sulfoxide, and 6.2 ppm sulfone). Residues in the leaves were proportional to the dosage applied to the soil. An average level of 4-6 ppm of the carbamate in the leaves provided satisfactory control of the spirea aphid. Similar results were found when the spirea aphids were fed on a synthetic diet containing similar levels of the insecticide. © 1979, American Chemical Society. All rights reserved.