Study on Substitutional Insecticides to Replace Hypertoxic Insecticides against Cotton Bollworm,Helicoverpa armigera

The effects characters and efficacies of 19 insecticides against Helicoverpa armigera were tested by using laboratorial egg-dipping,leaf-dipping,topical application bioassay and plot tests in the field. The indoor bioassay results showed that the hatching rate of cotton bollworm were significantly suppressed by spinosad,only 42.86% of the eggs hatched after treated by 90.40 mg/L spinosad. High mortalities of neonatal cotton bollworm occurred as they bored out from the eggs treated by methylaminoavermectin,spinosad,chlorpyrifos,lambda-cyhalothrin,phoxim,profenophos and beta- cypermethrin.All of these insecticides mentioned above are highly toxic to neonates,and their 1.0×104~2.0×104 times dilutions could kill 100% of the neonates.The results of growth regulators such as chlorfluazuron,hexaflumuron and methoxyfenozide were also effective to neonatal cotton bollworm,70% of the larvae died after separately treated by 1 000 times dilutions of these insecticides,while the development of survival larvae were obviously inhibited.Methylaminoavermectin,lambda-cyhalothrin,spinosad,chlorpyrifos,beta-cypermethrin,profenophos and phoxim were equally effective to young and old larvae.The results of plot tests showed that methylaminoavermectin,lambda-cyhalothrin,beta-cypermethrin and profenophos had high and quick effective,the corrected mortalities were 100% after treated with 4 000 times methylaminoavermectin dilution and 5 000 times lambda-cyhalothrin dilution.But the spinosad and methoxyfenozide acted slowly and their efficacies were lower. Consequently,methylaminoavermectin,lambda-cyhalothrin,spinosad,beta-cypermethrin,profenophos and methoxyfenozide can be used as substitutional insecticides to replace hypertoxic insecticides against H.armigera,if only spray insecticides in time at peak egg stage.