Bio-efficacy and Persistent Toxicity of Certain Insecticides against Rice Weevil, Sitophilus oryzae (Linn.) (Curculionidae: Coleoptera)

Spinosad 45 SC@ 0.05 mg a.i. cm⁻² (500 mg a.i. m⁻²) and malathion 50 EC @ 150 mg a.i. m⁻² caused cent per cent mortality of Sitophilus oryzae at 24 hours after treatment and 87.5 and 47.5 per cent mortality at 180 days after treatment. Spinosad recorded the highest average toxicity of 96.01 per cent and was found to be the most effective insecticide followed by malathion 50 EC with 65.71 per cent average toxicity. Spinosad recorded the highest persistence toxicity value of 17292.86 followed by malathion with persistence toxicity value of 11828.57 on jute cloth disc.