Study On The Risk Assessment Of Neonicotinoid Insecticides On Three Species Of Trichogramma

Natural enemy insects are an important natural resource for Integrated Pest Management?IPM?.In recent years,Trichogramma spp,as an egg parasitic wasp,is the most widely studied and applied natural enemy of insect pests.In recent decades,neonicotinoid insecticides have been playing an important role in the global pesticide market,but the environmental compatibility of neonicotinoid insecticides with natural enemies has been a controversial issue and has attracted extensive attention.In this study,through seven neonicotinoid insecticides?i.e.acetamiprid,imidacloprid,dinotefuran,thiamethoxam,clothianidin nitenpyram and thiacloprid?on three representative Trichogramma spp?T.dendrolimi,T.ostriniae and,T.confusum?the acute toxicity effect and toxicity of sublethal effects of study,to elucidate the safety risk of neonicotinoid insecticides against trichogramma,for the protection of natural enemy insects,guiding the scientific and rational use of drugs in the field,coordinate the relationship between biological control and chemical control,provide the theoretical basis.The main findings are as follows:1.The results of acute toxicity test of neonicotinoid insecticides to trichogramma spp showed that nitenpyram had the greatest intrinsic toxicity to T.dendrolimi and T.ostriniae and the value of LC₅₀ is 0.060,0.066 mg a.i./L,respectively.But for T.confusum,the most toxic neonicotinoid insecticide is dinotefuran and the value of LC₅₀ is 0.07 mg a.i./L.The neonicotinoid insecticides with the lowest acute toxicity to T.dendrolimi,T.ostriniaeand and T.confusum are acetamiprid,thiacloprid and thiacloprid respectively,and the LC₅₀ values were 1.20,1.19 and 1.73 mg a.i./L,respectively.Furthermore,based on the risk quotient estimation,neonicotinoid pesticides pose a risk to all three species of trichogramma.Comparatively,acetamiprid is the safest neonicotinoid insecticide,which belongs to low risk.The risk quotients are respectively 25.0 for T.dendrolimi,29.4 for T.ostriniae,25.4 for T.confusum.2.The results showed that neonicotinoid insecticides induced significant toxic effects on the parasitism of three Trichogramma spp.at low-lethal concentrations.Acetamiprid was considered to be the only safe neonicotinoid insecticide of T.dendrolimi and T.ostriniae.The value of EC50 is 3.72,1.102 mg a.i./L,respectively.The least toxic to T.confusum is thiacloprid with the value of EC₅₀ 1.225 mg a.i./L.Otherwise,The greatest influence on the parasitism of three species of trichogramma was dinotefuran.The value of EC50 is 0.033,0.038,0.0079 mg a.i./L,respectively.3.The effect of neonicotinoid insecticides on the eclosion rate of trichogramma showed that neonicotinoid insecticides had a significant effect.Acetamiprid had the least effect on the eclosion rate of T.dendrolimi and T.ostriniae with EC50 values of8.79?2.91 mg a.i./L.The least effect on T.confusum was thiacloprid with EC50value of 5.142 mg a.i./L.The most significant effect on the eclosion rate of the three species trichogramma was nitenpyram with EC50 values of 0.359?0.239?0.205 mg a.i./L,respectively.According to the study on acute toxicity and sublethal toxicity of neonicotinoids insecticides to three trichogramma,seven kinds of insecticides have higher toxicity to trichogramma and different degrees of influence on parasitism and eclosion rate of trichogramma adults.Among the neonicotinoid insecticides,only acetamiprid and thiacloprid had better environmental compatibility with trichogramma,while nitenpyram and dinotefuran had worse environmental compatibility.Therefore,attention should be paid to the influence of pesticides on trichogramma when used in outdoor fields or in greenhouses.Meanwhile,pesticides should be used in a scientific and reasonable way to better protect the natural enemy population and better combine chemical control and biological control,so as to maximize agricultural economic and ecological benefits.