Sublethal Effects Of Thiamethoxma And Clothianidin On Thichogramma Ostriniae (Hymenoptera: Thichogramma)

Trichogramma spp.an important natural enemy insect species of Lepidoptera pests,and it is widely used in biological control.At present,the study of pesticides sublethal effects on Trichogramma was rarely reported.Widely used of the neonicotinoid insecticides,in particular its harm to natural enemy insects has being widely disputed.Therefore,we examined the sublethal effects of the neonicotinoids thiamethoxam and clothianidin on T.ostriniae,to elaborate the neonicotinoid insecticide thiamethoxam,clothianidin safety on T.ostriniae.In order to coordinate the relationship between the chemical control and biological control,scientific guidance for safe and rational use of pesticides,effectively reduce the potential risk,which provides the theoretical foundation for the protection of natural enemy insects.The main findings are as follows:1.Acute toxicity and safety evaluation of thiamethoxam and clothianidin to adult of T.otriniae.Among the acute toxicity tested,thiamethoxma and clothianidin had a higher intrinsic toxicity to the thichogramma,with the LC50 values 0.185(0.139-0.266)and 0.255(0.176-0.441)mg L-1.The risk coefficient of two kinds of pesticides on T.ostriniae was 3243.24 and 2823.53.2.Sublethal effects of thiamethoxam and clothianidin on adult T.ostriniae.From the treatment by sublethal,the results we got that between parent and offspring the emergence rate,female-male ratio and single female parasite number have significant difference,the emergence rate increased with the sublethal concentration decreased(thiamethoxma:78.9%-73.7%;clothianidin:79.7%-68.9%),and compared with the parent,offspring emergence rate has significantly increased(thiamethoxma:81.0%-75.4%;clothianidin:81.7%-78.5%);but the female-male ratio and the single female parasite number were contrary,with the concentrations increased,the difference were more significant(female-male ratio P:thiamethoxma:1.896-2.497;clothianidin:2.027-2.538;Fi:thiamethoxma:1.846-2.224;clothianidin:1.846-2.271;the single female parasite number P:thiamethoxma:23.834-32.421;clothianidin:23.029-31.041;Fi:thiamethoxma:22.464-29.323;clothianidin:22.196-28.310).And then the development durations and adult longevity of T.ostriniae after treated with sublethal doses of the two insecticides had no obvious change compared with the control(P<0.05).3.Field recommended dosage effects of thiamethoxam and clothianidin on T.ostriniae.After treated with water,thiamethoxam and clothianidin field recommended doses to process the egg stage to pupal stage use eggs dipping method,the emergence rate,female-male ratio and single female parasitic number had significant effects,but no significant influence on adult longevity.Cmpared with the control the emergence rate had a significant decreased,after treated with the field recommended doses the emergence rate were 59.1%-77.6%and 49.9%-62.3%,respectively,and the emergence rate,eggs>larvae>prepupa>pupae.The female-male ratio compared with the control were also significant difference,the male and female ratio were 2.125-2.216 and 2.266-2.381,respectively.After treatment,the single female parasite number reached 34.559-35.084 and 33.267-34.703,respectively,and the highest was 1.79 and 1.76 times than the control(P<0.05).4.Sublethal effects of thiamethoxam and clothianidin on enzyme of T.ostriniae.From the experimental results,after treated with the thiamethoxam and clothianidin sublethal doses on adults of T.ostriniae,the GSTs,AChEs and cytochrome P450 enzyme activities were affected with various degrees,the results show that the GSTs activitie of T.ostriniae was inhibited,and the AChEs and cytochrome P450 enzyme activities of T.ostriniae enhanced obviously after the treatment with the thiamethoxam and clothianidin sublethal doses.In this article,through the neonicotinoid insecticide thiamethoxam and clothianidin research on T.ostriniae,we found that the toxicity of two pesticides on T.ostriniae were highest,and the emergence rate,female-male ratio,single female parasitic number and enzyme activity of trichogramma were all affected with various degrees.Therefore,when used in the field,we should pay attention to the effects of insecticides on trichogramma,and use the insecticides rational to protect the natural enemy species better.Then makes the combination of biological control and chemical control preferably,and let the control effect of optimization.