Factors Influencing the Systemic Insecticidal Action of Substituted Phenyl Dimethyl Phosphates1

Abstract

p32-radiotracers of 2,4,5-trichlorophenyl dimethyl phosphate (A), 4-methythiophenyl dimethyl phosphate (B), and 4-nitrophenyl dimethyl phosphate (C) were used to study the systemic insecticidal activity of these compounds in cotton plants following application to the stem or as a 5% granule to the soil about the roots. Although all 3 compounds are effective contact insecticides, neither A nor C was appreciably active as a systemic insecticide find only traces of the intact insecticides could be found in the leaves up to 32 days after treatment. However B is an active systemic insecticide and this observation was in agreement with the findings of the radiotracer investigations which showed relatively large amounts of B or its toxic oxidation products in leaves and squares. It was concluded that B was more soluble in the lipoid cuticle of the cotton plant and that its oxidation in the plant environment to the more toxic sulfoxide and sulfone derivatives provided the necessary “delay factor” so that it was translocated in lethal amounts.