Sublethal Effects Of Three Kinds Of Insecticides On Eretmocerus Mundus

Bemisia tabaci is a kind of harmful polyvorous pest,which is widely distributed in the world.Eretmocerus sp.is the dominant obligate parasitic wasp of B.tabaci.In this study,mitochondrial mt DNA COⅠgene was used as a molecular marker to identify and analyze the genetic diversity of 10 geographic populations of Eretmocerus sp.from7 regions in Tianjin.The indoor virulence of dimpropyridaz,afidopyropen and fluralaner against Eretmocerus sp.was determined.The safety of the wasps was evaluated according to the selected virulence index.The effects of these three insecticides on the biological characteristics of the wasps were investigated at sub-lethal concentration(LC₁₅)and lethal medium concentration(LC₅₀)levels.The effect of these three insecticides on the control of B.tabaci in greenhouse and on the population dynamics of Eretmocerus sp.in greenhouse were studied by field experiments.（1）Molecular identification and genetic diversity analysis of Eretmocerus sp.in Tianjin:73 Eretmocerus mundus were collected from 6 areas of Wuqing,Jinghai,Ninghe,Baodi,Beichen and Xiqing,and 18 Eretmocerus sp.WTT-2016 were collected from 4 areas of Xiqing,Jinghai,Baodi and Jizhou.The genetic differentiation coefficient of Baodi population of E.mundus was the highest among 6 different geographical populations,while Jinghai population was the most conservative.The genetic differentiation index of Baodi district population of E.sp.WTT-2016 was the highest,while the population of Jizhou district was the most conservative.Thirteen haplotypes of E.mundus and fourteen haplotypes of E.sp.WTT-2016 were defined by sequence analysis.Among them,the haplotype MHap＿1 and hahaplotype MHap＿2 of E.mundus and the haplotype SHap＿1 of E.sp.WTT-2016 are the most frequent and widely distributed,which can be considered as the relatively primitive dominant haplotypes in their respective populations.There are both gene exchange and genetic differentiation among geographical populations.The mismatch analysis showed that the population of E.mundus existed stably in Tianjin,and the population of E.sp.WTT-2016existed for a short time and had strong adaptability and genetic variation.（2）The indoor toxicity and safety evaluation of three insecticides to E.mundus:The indoor toxicity of E.mundus to three insecticides,which were dimpropyridaz,afidopyropen and fluralaner,was determined by the glass tube film method.The order of toxicity was fluralaner>dimpropyridaz>afidopyropen.The selective toxicity indices of the three insecticides showed that the positive selectivity of afidopyropen and dimpropyridaz ester was positive,while the negative selectivity of fluralaner was negative.（3）Effects of three insecticides on biological characteristics of E.mundus:The sublethal concentrations(LC₁₅)and medium lethal concentrations(LC₅₀)of dimpropyridaz,afidopyropen and fluralaner had certain effects on E.mundus.Except for the doses of dimpropyridaz,afidopyropen and fluralaner LC₁₅ and LC₅₀,the longevity of E.mundus was significantly shortened.The parasitism rate of female adult wasps was significantly decreased under the treatment of afidopyropen and dimpropyridaz ester,while the parasitism rate of female wasps was significantly increased under the treatment of flurellana LC₅₀.Both afidopyropen and dimpropyridaz ester significantly prolonged the progeny developmental time,but fluralaner LC₁₅ dose had no significant effect on the progeny developmental time.Both afidopyropen and fluralaner LC₅₀ doses significantly reduced the eclosion rate of the offspring,while afidopyropen had no significant effect.（4）Effects of three insecticides on greenhouse population dynamics of Eretmocerus sp.and B.tabaci（MED）:The results of field experiments showed that all three insecticides had good control effect on B.tabaci（MED）,and the order of control effect on B.tabaci（MED）was afidopyropen>dimpropyridaz>fluralaner.After the treatment of the three insecticides,the greenhouse population of Eretmocerus sp.decreased significantly.The effect of fluralaner on the greenhouse population of Eretmocerus sp.was relatively small.In this study,it was found that temperature was an important factor that restricted the population dynamics of Eretmocerus sp.in greenhouse.To master the population dynamics of Eretmocerus sp.under natural temperature changes could provide experimental basis for the field application of Eretmocerus sp.