Toxicity of some insecticides against seven day old larvae of Bihar hairy caterpillar, Spilarctia obliqua Walker

Abstract

The stomach toxicity of some insecticides viz., Cypermethrin, Lambda cyhalothrin and Chlorpyriphos were determined against 7d old larvae of Spilarctia obliqua by leaf dip method. Cypermethrin was found to be the most toxic insecticide during observation at 18, 24, 48 and 72 HAF. On the basis of LC50 values at different time intervals the order of toxicity was, Cypermethrin > Lambda cyhalothrin > Chlorpyriphos and the LC50 (%) values being 0.003, 0.054, 0.107 at 24 HAF, 0.002, 0.045 and 0.101 at 48 HAF, 0.016, 0.039 and 0.085 at 72 HAF respectively. A comparative dose mortality (50%) response expressed in terms of relative toxicity indicated that RT values for Cypermethrin, Lambda cyhalothrin, and Chlorpyriphos were 35.66, 1.98 and 1.00 at 24HAF, 50.5, 2.24 and 1.00 at 48 HAF, 5.31, 2.17 and 1.00 at 72 HAF. Chlorpyriphos in particular, showed very low RT value indicating far less stomach toxicity to S. obliqua as compared to Cypermethrin and Lambda-cyhalothrin. These findings can be helpful for the selection of suitable insecticides for effective pest management under field condition.