author(s)
M Mahesh, V Sunitha, J Satyanarayana, TVK Singh and R Jagadeeshwar

abstract
The present investigation was conducted on relative toxicity of four new insecticide molecules against third instar larvae of tobacco caterpillar Spodoptera litura (Fab.) by using leaf dip bioassay technique under laboratory conditions at Department of Entomology, College of Agriculture, Rajendranagar, Hyderabad. The egg mass of Spodoptera litura was collected from Rangareddy district and reared under laboratory condition until pupation on castor leaves. Sexing was done at pupal stage. After adult emergence, single female was paired with male kept in a plastic jar, provided with white paper as substrate for egg laying. Collected these eggs and after hatching the larvae were reared on castor leaves under laboratory condition. The third instar larvae were used for bioassay. Among the various insecticides tested, chlorantraniliprole was found to be most toxic with least LC₅₀ value (0.0055%) followed by chlorfenapyr, thiodicarb and chlorpyriphos. The order of toxicity based on LC₅₀ values was chlorantraniliprole (0.0055%) > chlorfenapyr (0.0073%) > thiodicarb (0.019%) and chlorpyriphos (0.0232%) respectively, and chlorantraniliprole, chlorfenapyr and thiodicarb showed 4.21, 3.17 and 1.22 times toxic over chlorpyriphos at 72 hours after exposure.