Department of Entomology, H.P. Krishi Vishvavidyalaya, Palampur-176 062, Himachal Pradesh (India).
*Present address: Assistant Entomologist, HPKV Rice Research Station, Malan-176 047, District Kangra, Himachal Pradesh (India).
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.
