An Evaluation on Acute Toxicity of 29 Pesticides to Bombyx mori

The acute toxicity of 29 pesticides to silkworm,Bombyx mori,was evaluated in laboratory by using the leaf dipping method.The results indicated that LC50 of abamectin,spinosad,cypermethrin·chlorpyrifos,and imidacloprid was 0.002 0,0.089 1,0.214 5,and 0.272 9 mg/L respectively,being pesticides of virulent toxicity grade.The LC50 of abamectin·Bacillus thuringiensis,carbosulfan,trichlorfon,pyrethrins·celastrusangulatus,profenofos,Bacillus thuringiensis·chlorpyrifos,and nicotine was 0.692 1,0.769 6,0.850 2,0.744 9,2.513 4,1.732 7,7.260 4 mg/L respectively,being pesticides of high toxicity grade.All the other pesticides were of moderate or low toxicity grade.Pesticides of virulent and high toxicity grade should be forbidden to use in silkworm rearing areas.Pymetrozine is of low toxicity grade.Yet the residual toxicity period,chronic toxicity and infectivity should be considered if pesticides of low toxicity grade are to be used in silkworm rearing areas.