| As is known,in the process of agricultural production,the prevention and control of crop diseases and insect pests is a key link to ensure the safety of production,so chemical and biological control is a very important means to control pests and diseases.Chemical pesticides are widely used in crops because of their broad spectrum and high efficiency,but they also bring about the destruction of farmland ecosystem and the destruction of biodiversity.Due to the strengthening of people’s awareness of environmental protection and safety,biological control technology,especially the natural enemies of insects(such as Trichogramma etc.)has been widely used in agricultural production,chemical pesticides,because of their characteristics,will not only kill pests,but also affect the survival of natural enemies.At present,the existing studies on the safety evaluation and risk assessment of natural enemies are not complete,therefore,the safety evaluation on pesticides against natural enemies,and the determination on the lethal effect of various pesticides on natural enemies can provide scientific basis for the rational selection and spraying of pesticides in farmland.In this paper,under laboratory conditions,the risk assessment and safety assessment were carried out on the determination of the acute toxicity of Trichogramma ostriniae,Trichogramma chilonis,and Trichogramma dendrolimi by sensitive layer method via 2 chemical pesticides of nicosulfuron and Chlorantraniliprole,as well as 2 biological pesticides of Bacillus thuringiensis and Symbiotic toxin;and then on the basis of the sensitivity analysis of differences between the 3 Trichogramma Species against different kinds of pesticides,the pesticide toxicity grade evaluation was carried out to select highly toxic pesticides and low toxicity pesticides for the study on the sublethal effect of survival and reproduction of 4 kinds of pesticides to 3 Trichogramma Species.The main research contents and results are as follows:In this study,the acute toxicity of chemical pesticides on 3 Trichogramma Species was determined,and the safety was evaluated The sensitive layer contact exposure method was used to compare the death and survival rate of 3 species of Trichogramma,results showed that the LC50 of Nicosulfuron to Trichogramma dendrolimi,T.ostriniae,T.chilonis were respective 351.81,31.96 and 3.93 mg/L,and low risk,high risk,high risk to the safety of 3 Trichogramma Species.And the LC50 of Chlorantraniliprole to Trichogramma dendrolimi,T.ostriniae,T.chilonis were respective 7.17,2.85 and 0.0076 mg/L,and medium risk,high risk,extreme high risk to the safety of 3 Trichogramma Species.Then,the acute toxicity of biological pesticides on 3 Trichogramma Species was determined,and the safety were evaluated.The sensitive layer contact exposure method was used to compare the death and survival rate of 3 species of Trichogramma,results showed that the LC50 of Bt to T.dendrolimi,T.ostriniae,T.chilonis ere respective 254.17,56.52 and 195.06 mg/L,all medium risk of this pesticide to the safety of 3 Trichogramma Species;and the LCs0 of symbiotic toxin to T.dendrolimi,T.ostriniae,T.chilonis were respective 27670.4,1198.94 and 89825.24 mg/L,and the safety of this pesticide to 3 Trichogramma species were all:low risk.Subsequently,the sublethal effect of chemical pesticides to 3 Trichogramma Species was studied.The sensitive layer contact exposure method was used to prepare the LC30 concentration of Nicosulfuron and Chlorantraniliprole into sensitive layer,and the Trichogramma was made to contact with these 2 chemical pesticides,then the results of survival and reproduction were compared.Results indicated that the Chlorantraniliprole had most significant influence on the survival and reproduction of T.ostriniae,followed by T.chilonis,then T.dendrolimi.Nicosulfuron had some effect on Trichogramma ostriniae and T.dendrolimi but not significant.Finally,the sublethal effect of biological pesticides to 3 Trichogramma Species was studied.The sensitive layer contact exposure method was used to prepare the LC30 concentration of Bt and Bt toxin into sensitive layer,and the Trichogramma was made to contact with these 2 biological pesticides,then the results of survival and reproduction were compared.Results indicated that Bt had impact on 3 species of Trichogramma,where the T.ostriniae was most strongly affected,its survival rate,fecundity and off spring eclosion rate were significantly lower than those of the other two Trichogramma Species. |
