Susceptibility status of castor semilooper, Achaea janata Linn. to pyrethroids and non-pyrethroid insecticides during the last decade

The relative toxicity of emulsions of various pyrethroids and non-pyrethroid insecticides was evaluated against the larvae of Achaea janata Linn. in the laboratory. On the basis of LC₅₀ values, lambdacyhalothrin, cypermethrin, deltamethrin, fenpropathrin, fenvalerate, methyl parathion and pyrethrin were respectively 240.4, 64.7, 51.4, 23.9, 17.6, 7.5, and 4.1 times more toxic than endosulfan. The remahing two insecticides, viz., malathion and lindane were less toxic than endosulfan i.e., about 0.67 and 0.64 times, respectively as toxic as endosulfan. Although there was an increase in the LC₅₀ values of lindane, malathion, fenvalerate, cypermethrin, endosulfan and deltamethrin since 1983, the shift in the level of susceptibility of A. janata to these insecticides was not pronounced. This was exemplified by their respective low relative susceptibility values, i.e., 3.8, 3.6, 3.0, 2.9, 2.9 and 1.5. A comparison of the relative resistance based on LC₅₀ values of A. janata, Spilosoma obliqua Wlk. and Spodoptera litura (Fabr.) to insecticides indicated higher susceptibility of A. janata amongst these three pests.