Occurrence of insecticide resistance in leafhopper, Amrasca biguttula biguttula (Ishida) on Okra

Insecticides are proving ineffective against the adults of Amrasca biguttula biguttula on okra at Hisar. Toxicity of various insecticides viz., malathion, oxydemeton methyl, phosphamidon, dimethoate, thiamethoxam, endosulfan and monocrotophos was studied against this leafhopper and the LC50 values (%) were 1.097, 0.126, 0.112, 0.178, 0.000447, 0.063 and 0.063, respectively. Thiamethoxam was the most toxic i.e. 2454 times more toxic than malathion which was least toxic. Imidacloprid gave more than 80 per cent mortality of this pest at 4 times lower the normal concentration (0.000225%) while fenvalerate could not bring about even 20 per cent mortality at 30 times the normal concentration (0.15%) indicating development of resistance in leafhopper to the commonly recommended insecticides.