Influence of insecticides on dehydrogenase activity (DHA) in rice soil

A lab study was conducted to investigate the effect of five insecticides viz, chlorantraniliprole, imidacloprid, dinotefuran, pymetrozine, cartap hydrochloride on dehydrogenase activity (DHA) in black clay and sandy clay loam soils collected from rice fields. Chlorantraniliprole at both recommended dose (RD) and double the recommended dose (DRD) had no inhibitory effect on soil microbes in both sandy clay loam and black clay soil up to 20 days after insecticide application (DAA). Cartap hydrochloride at DRD had slight inhibitory effect on DHA up to 24 h after insecticide application (HAA). Imidacloprid at both RD and DRD resulted in significant drop in the DHA of both the soils up to 20 DAA. Dinotefuran at both RD (51.2 μg TPF g^-1 soil) and DRD (43.1 μg TPF g^-1 soil) had inhibitory effect only up to 24 HAA in sandy clay loam soil. Pymetrozine at DRD had significant inhibitory effect even up to 10 DAA and 20 DAA.