Toxicity Determination of Several Insecticides against Cnaphalocrocis Medinalis(Gunenée)

[Objective] The study aimed to determine the toxicity of several insecticides against Cnaphalocrocis medinalis(Gunenee),and provide a base for controlling Cnaphalocrocis medinalis(Gunenee).[Method] With the 3th instar larvae of Cnaphalocrocis medinalis(Gunenee) as tested larva,seven kinds of insecticides were diluted as five series of concentration,the mortality of the tested insects were investigated after treating by insect-soaking method for 48 h(96 h treated with Monosultap).[Result] Monosultap had a lowest toxicity to C.medinalis with LC50 of 306.624 2 mg/L.Avermectins had a highest toxicity with LC50 of 0.221 0 mg/L and Fipronil's LC50 was 7.237 5 mg/L,being only lower than Avermectins'.Based on their toxicity to C.medinalis,the tested 7 insecticides were arranged in decreasing order as Avermectins Fipronil Hexaflumuron Profenofos Chlorpyrifos Triazophos Monosultap.Control efficacy of 1.8% Avermectins EC at 8.1 g(a.i) /hm2 and 40% Profenofos EC at 480 g(a.i) /hm2 was 86.68% and 81.72% resp.after applying insecticides for 10 d.[Conclusion] Profenofos,Avermectins,Fipronil and Hexaflumuron had a good control efficacy in the field,and applying their mixtures could have a better control efficacy against C.medinali.