Residual toxicity of some important insecticides against Amrasca biguttula biguttula Ishida infesting okra

The residual toxicity of four insecticides, viz, carbaryl, endosulfan, malathion and monocrotophos at 0.10, 0.07, 0.08 and 0.05 per cent respectively, was determined against the second instar nymphs of Amrasca biguttula bigutulla Ishida infesting okra leaves. The PT values for carbaryl, endosulfan, malathion and monocrotophos were 503.12, 406.08, 219.84 and 1034.08, whereas LTSo values were 4.10, 1.64, 1.24 and 7.72, respectively. The order of relative toxicity on the basis of PT and LTSo values remained the same. Monocrotophos was the most effective insecticide followed by carbaryl, endosulfan and malathion.