Base-line values for susceptibility of Spodoptera litura Fab. (Lepidoptera: Noctuidae) to different insecticides

The base-line values for insecticide susceptibility in Spodoptera litura were established for twelve different insecticides by employing standard bioassay techniques. The susceptible strain of S. litura which was reared for 24 generations under insecticide free conditions was used in the study. The median lethal doses (LD_50s) of different insecticides ranged from 0.19 to 16.46 ?g a.i. g-1. Among the conventional insecticides, chlorpyriphos was highly toxic to the laboratory reared susceptible strain followed by quinalphos, cypermethrin, profenofos and endosulfan. However, monocrotophos and fenvalerate were least toxic to the susceptible strain. Based on the median lethal concentrations (LC_50s), it was noticed that methomyl was more toxic to the susceptible strain than a Bt kurstaki product, Dipel 8L. Of the three newer insecticide molecules, indoxacarb was more lethal to the susceptible strain followed by novaluron and spinosad.