Residue Analysis of Leptophos, Its Oxygen Analogue, and Its Phenol in Field-treated Wheat Plants2

Abstract

Field-grown plants were treated at the early tillering stage with leptophos (0-[4-bromo-2,5-dichlorophenyl] O -methyl phenylphosphonothioate) EC, 1970 formulation, at 0.56 and 1.12 kg Al/ha. Recoveries from fortified plant samples ranged from 70 to 102% for leptophos, from 51 to 99% for its oxygen analogue ( 0 -[4-bromo-2,5-dichlorophenyl] O -methyl rhenylphosphonate), and from 68 to 97% for its pheno (4-bromo-2,5-dichlorophenol). Straw harvested 63 days posttreatment contained 0.07 ppm or less leptophos, 0.01 ppm or less of the phenol, and the oxygen analogue was not detectable (<0.02 ppm). Residues were not detected in the wheat kernels. The leptophos residue was diluted by plant growth, but the main disappearance of leptophos appeared to be due to degradation or physical losses, or to both.