Detection of Possible Resistance in Mustard Aphid Lipaphis erysimi Kalt. to Various Insecticides Used for over a Decade

Relative toxicity of emulsions of seven proprietary formulations of insecticides was evaluated against Lipaphis erysimi Kalt. in the laboratory. On the basis of LC50 values, lambda cyhalothrin, fluvalinate, deltamethrin, cypermethrin and fenvalerate were respectively 24.9, 17.8, 4.3, 3.0 and 1.8 times as toxic as fenpropathrin. All the synthetic pyrethroids were relatively more toxic than commonly used endosulfan. Although there was an increase in the LC50 values of fenpropathrin and endosulfan since 1988, the shift in the level of susceptibility of L. erysimi to these insecticides was not pronounced. This is exemplified by low relative susceptibility values i.e. 2.00 and 1.44, respectively. The toxicity of deltamethrin, cypermethrin, and fenvalerate was more or less the same even after a lapse of 12 years.