Screening Of Activity And Synergistic Additives Of Cynanchum Komarovii Extracts And Plant Essential Oil On Aphis Sp.

As a characteristic agricultural industry in Ningxia,the large-scale occurrence of aphids seriously affects the yield and quality of wolfberry.At present,chemical control is a common method to control Aphis sp..Due to long-term use,the problems of drug resistance and excessive pesticide residues in wolfberry begin to appear.With the economic development and social progress,people’s demand for environmentally friendly pesticides is gradually increasing.The development and application of botanical insecticides has gradually become a trend.The extracts of Cynanchum komarovii has gradually begun to be used as a new insecticide,but as a new botanical insecticide,there is a problem of low control effect.The control effect of C.komarovii extracts can be improved by adding spray adjuvant or compounding with other botanical insecticides.In this study,the indoor toxicity of C.komarovii extracts to Aphis sp.was determined.The synergistic effect of spray adjuvants on the control of Aphis sp.by C.komarovii extracts was determined by indoor toxicity determination,and the reasons for the synergistic effect were evaluated by analyzing the surface tension of the liquid and the wetting performance of wolfberry leaves.Though screening plant essential oils,the essential oils with high contact activity were selected and compounded with C.komarovii extracts to determine the compounding ratio.The plant essential oil was processed into microcapsules,and the optimal combination of control effect was determined by pot efficacy test.The main results are as follows:The toxicity of water extracts of C.komarovii on Aphis sp.was studied.The results showed that the toxicity of C.komarovii extracts to aphids increased gradually with the prolongation of time.The LC₅₀was 178.404 mg/L at 24 h and 42.554 mg/L at 48 h after treatment.The synergistic effect of spray adjuvant on the control of Aphis sp.by C.komarovii extracts aqueous solution was studied,and the synergistic reason was analyzed by the influence of the surface tension of the liquid and the wetting of the wolfberry leaf surface.Adding different concentrations of various additives can improve the toxicity of the liquid to the Aphis sp..The addition of 100 mg/L methyl oleate and 200 mg/L silicone were 3.06times and 2.28 times that of the control group,respectively,and the synergistic effect was the most obvious.By measuring the surface tension,contact angle and retention of the liquid after adding spray adjuvants,it was found that oil adjuvants such as methyl oleate and GY-Tmax mainly increased the retention of the liquid,improved wetting and penetration of aphids,and increased virulence;surfactant additives such as silicone S618 and AEO-5mainly increased the wetting area of the liquid by reducing the surface tension of the liquid and the contact angle on the leaf surface of wolfberry,thereby increasing the toxicity to aphids.The contact toxicity of four plant essential oils to Aphis sp.was studied.The results showed that eugenol had the highest contact toxicity to Aphis sp.,and the LC₅₀was 160.101mg/L.The joint toxicity of C.komarovii extracts and eugenol on aphids was determined.When the compound ratio was 1:3,the co-toxicity coefficient was the largest and the synergistic effect was the most significant.Due to eugenol is volatile and exposed to air for a long time,it is easy to cause deterioration.Therefore,eugenol is processed into microcapsules to reduce volatilization and prolong the action time.The control effects of different combinations on Aphis sp.were compared by pot experiment.The control effects of 1,3 and 7 days after application were investigated.It was found that the addition of methyl oleate or eugenol microcapsules alone could significantly improve the control effect of C.komarovii extracts on Aphis sp.,and the control effect was the highest when methyl oleate and eugenol microcapsules were added at the same time,and the control effect was more than 90%after 1-7 days.The above results showed that the addition of spray adjuvants increased the toxicity to aphids by affecting the surface tension of the liquid and improving the wetting of the liquid on the leaf surface.On the other hand,the combination with eugenol and other plant essential oils can also improve the toxicity of the aqueous extracts of C.komarovii.The processing of eugenol into microcapsules can delay its volatilization rate and increase the action time.By screening the best formula,delaying the production of resistance and reducing pesticide residues on wolfberry fruit,it has certain development and application potential.