Quantitative structure-activity studies of benzoylphenylurea larvicides: II. Effect of benzyloxy substituents at aniline moiety against Chilo suppressalis Walker

Abstract

The larvicidal activity of a series of N-2,6-difluorobenzoyl- N′-[4-(substituted benzyloxy)-phenyl]-ureas against nondiapause larvae of the rice stem borer, Chilo suppressalis Walker, was measured by a topical application method under conditions in which oxidative metabolism was inhibited by piperonyl butoxide. The effects of the substituted-benzyloxy moiety on variations in the activity were analyzed quantitatively using physicochemical substituent parameters and regression analysis. Results were compared with those found previously for N-2,6-difluorobenzoyl- N′-(4-substituted phenyl)-ureas, indicating that the electron-withdrawing property of the anilide substituents participates in determining the activity through the inductive effect. The hydrophobicity of the total anilide substituents favors activity, whereas the steric dimension in terms of the width lowers it. Although inhibition of new cuticle formation on cultured integument of diapausing larva could not be determined accurately for most of the compounds because of their limited solubility in the assay medium, inhibitory activity seemed related to larvicidal activity, as was the case for previously investigated simpler congeners.