Insecticides Screening For Aphis Craccivora Of Astragalus Membranaceus And Determination Of Pesticide Residues

Aphis craccivora is an important agricultural pest in China,which mainly damages legumes.Aphids are one of the main pests of Astragalus membranaceus,In recent years,with the growing area of Astragalus membranaceus,its damage to Astragalus membranaceus is also increasing year by year.The control of Aphis craccivora in my country is mainly based on chemical control.However,as a Chinese medicinal material,Astragalus membranaceus have not been registered for the prevention and control of Aphis craccivora.The toxicities of six insecticides against A.craccivora were determined.Field control and pesticide residue detection were assessed with the high-efficiency and low-toxicity insecticides according to the toxicities in laboratory.The results are as following:1.The toxicities of six insecticides against A.craccivora were determined by the insect-dipping method.The results showed that 5% abamectin EC was the most toxic with LC₅₀ value of 0.08 mg/L,followed by 10% flonicamid(LC₅₀ was 0.148mg/L),22.4% spirotetramete(LC₅₀ was 0.189mg/L),1.5%pyrethrins EW(LC₅₀ was 0.192mg/L).Field control was assessed with three effective insecticides according to the toxicities in laboratory.The results showed that the control efficacy of 2500,3000 and 4000 times of flonicamid was more than 80% after 1 day,significantly better than abamectin and pyrethrins.The control efficacy of 2500-4000 times of flonicamid,4000-5000 times of abamectin and 3500 times of pyrethrins were significantly increased to 90% after 5 days treatment.Therefore,4000 times of flonicamid,5000 times of abamectin and 3000 times of pyrethrins are the best insecticides and concentrations for controlling Aphis craccivora in Astragalus membranaceus crops.2.A rapid method was developed for the determination of flonicamid and pyrethrin in Astragalus membranaceus by ultra performance liquid chromatography coupled with tandem mass spectrometry（UPLC-MS/MS）.The linearities of flonicamid,pyrethrin I and pyrethrin II were satisfied with correlation coefficents above 0.999 in the range of 0.01⁰.10 μg/m L.The mean recoveries ranged from 80.07% to105.69% with the relative standard deviations（RSDs）of 1.01%¹3.06% at fortification levels of 0.01,0.10 and 0.20 mg/kg.The limits of quantification（LOQs）were both 0.01 mg/kg.The results showed that the method was suitable for the determination of flonicamid and pyrethrin in Astragalus membranaceus.3.The terminal residues and dietary risk assessment of flonicamid and pyrethrin were tested in Astragalus membranaceus.The maximum residue limits of flonicamid and pyrethrin in Astragalus membranaceus were lower than 0.01 mg / kg after 21 days,which were far lower than the maximum residue limits of flonicamid and pyrethrin in other crops.Based on the terminal residue data,the national estimated daily intakes（NEDIs）of flonicamid and pyrethrin in general population were both 0.0015 mg,and the risk quotient was 0.32‰ and 0.57‰,respectively.Flonicamid and pyrethrin might not cause unacceptable risk to the health of the general population at the dosage of 66.67 g/hm² 和 8.33 g/hm²,respectively.