Relative toxicity of some important insecticides with particular reference to change in susceptibility level of Bagrada cruciferarum Kirk. during the last quarter century

Fifteen insecticides were tested as contact poisons against the adults of painted bug, Bagrada cruciferarum Kirk., infesting mustard. On the basis of LC50 values, lambdacyhalothrin, chlorpyriphos, cypermethrin, lindane, fenvalerate and fluvalinate were respectively, 30.94, 26.88, 7.25, 5.89, 5.78, 3.82, 3.68, 3.02, 1.87, 1.47 and 1.19 times as toxic as endosulfan. The remaining three insecticides, viz, methyl demeton, pyrethrin and malathion were less toxic than endosulfan i.e., about 0.46, 0.40 and 0.32 times, respectively, as toxic as endosulfan. A comparison of LC50 values for commonly used and recommended insecticides determined during the last quarter century (1971–1997) revealed a shift in the level of susceptibility of painted bug to pyrethrin, malathion, methyl demeton, endosulfan, fenitrothion, lindane and fenthion. There was about 8.92, 8.36, 4.19, 2.95, 2.59, 2.15 and 1.19-fold increase in the LCSo values of these insecticides. The base-line data thus generated would provide a record for detecting resistance level of B. cruciferarum to various insecticides at different periods.