Analysis Of The Minimum Effective Dose And Residual Dynainics Of Two Pesticides On Two Vegetable Pests

Pieris rapae and Myzus persicae are the main pests on vegetables,and their damage will cause vegetable yield loss and quality decline.Long-term large-scale use of chemical pesticides to control vegetable pests will cause pesticide residues in agricultural products to exceed the standard,pest resistance will increase,control costs will increase,and environmental pollution will increase.In this study,field efficacy trials were conducted to clarify the use of 2.5%efficient cyfluthrin aqueous emulsion to control P.rapae,70%imidacloprid water dispersible granules to prevent cabbage M.persicae and 2.5%high-efficiency cyhalothrin aqueous emulsion to control the minimum effective dose of M.persicae on pakchoi,and the study of pesticide residues on pakchoi and cabbage after the application of two chemical agents provides a scientific basis for the reduction of pesticide application.1 The lowest effective dose of the two insecticides in Anhui,Hebei and Hainan ProvinceIn the test,the low value of the registered dosage of 2.5%high-efficiency cyfluthrin aqueous emulsion(5.625～8.438 g a.i./hm2)was X,and the four doses were set to 0.50 X(2.813 g a.i./hm2),0.75 X(4.219 g a.i./hm2),1.00 X(5.625 g a.i./hm2)and 1.50 X(8.438 g a.i./hm2),The low value of the registered dosage of 70%imidacloprid water dispersible granules(21.00～31.50 g a.i./hm2)is Y,and the four doses were set to 0.50 Y(10.50 g a.i./hm2),0.75 Y(15.75 g a.i./hm2),1.00 Y(21.00 g a.i./hm2)and 1.50 Y(31.50 g a.i./hm2),In the field of Anhui,Hebei and Hainan Province,the field efficacy tests of the above two insecticides against cruciferous vegetable M.persicae and P.rapae in the open field were carried out by conventional spraying methods.The results show that,(1)In the Hebei region,the 2.5%high-efficiency cyhalothrin aqueous emulsion can be used to control M.persicae on pakchoi.A dose of 4.219 g a.i./hm2 can be used.70%imidacloprid water dispersible granules can be used to control M.persicae on cabbage,it is recommended to use the dose of 15.75 g a.i./hm2,which can achieve better control effect.(2)In Hainan area,2.5%high-efficiency cyfluthrin aqueous emulsion should be chosen to control M.persicae on pakchoi with the dose of 8.438 g a.i./hm2;70%imidacloprid water dispersible granules should be chosen to control M.persicae on cabbag with the dose of 21.00 g a.i./hm2.(3)70%imidacloprid water dispersible granules should be chosen to control M.persicae in Anhui region with the dose of 10.5 g a.i./hm2;2.5%high-efficiency cyfluthrin aqueous emulsion should be chosen to control M.persicae on pakchoi with the dose of 4.219 g a.i./hm2;2.5%high-efficiency cyfluthrin aqueous emulsion should be chosen to control P.rapae.with the dose of 5.625 g a.i./hm2.The prevention effect of using the above dose of medicament can reach more than 85%.The minimum effective dose of 2.5%high-efficiency cyhalothrin aqueous emulsion and 70%imidacloprid water dispersible granules to control cruciferous vegetable M.persicae in Hebei and Anhui is similar,and both are significantly lower than the minimum value of the recommended dose of pesticide products.In Hainan,due to the higher temperature,more generations of M.persicae occur,and the resistance level is higher.The minimum effective dose for controlling M.is the recommended dose for pesticide products,continue to increase the pesticide dosage will not significantly improve the control effect.2 Dynamic analysis of pesticide residues of two pesticides in Anhui ProvinceIn the field experiment of pharmacy in Anhui region,two pesticides were used to control insect pests,and pesticide residues were tested on pakchoi and cabbage.The half-lives of 0.5%X,0.75 X,1.00 X and 1.50 X doses of 2.5%cyfluthrin aqueous emulsion on Chinese cabbage were 2.89 d,3.75 d,3.12 d and 2.86 d.Combined with the results of field efficacy tests,4.219 g a.i./hm2 dose of 2.5%lambda-cyhalothrin has the longest half-life in Chinese cabbage,and the control effect reaches more than 85%,therefore,this dose is the lowest effective dose for controlling M.persicae on Chinese cabbage.The half-lives of 70%imidacloprid water dispersible granules in cabbage at the doses of 0.50 X,0.75 X,1.00 X and 1.50 X on cabbage were 1.50 d,1.78 d,1.45 d and 1.79 d.Combined with field efficacy trials in Anhui,the half-life of 70%imidacloprid water dispersible granules at a dose of 10.5 g a.i./hm2 is similar to that of high-dose,and the control effect reaches more than 85%,therefore,this dose is the lowest effective dose for controlling aphid in open field cabbage.Pesticide residue dynamic analysis and field efficacy test results show that when the application dose reaches a certain level,the control effect will not be improved obviously with increasing pesticide dose,therefore,controlling vegetable pests with the lowest effective dose of pesticides can not only achieve the expected prevention effect,but also reduce agricultural production costs and reduce environmental pollution.This study provides a scientific basis for the reduction of pesticide application.