Residual Fate Of Three Pesticides On Tea Plants And Control Effect Of Tea Leafhopper,Empoasca Onukii Matsuda

Tea green leafhopper?Empoasca onukii matsuda?is a serious pest in China's tea areas,and chemical pesticides are still one of its important control methods.Bifenthrin,indoxacarb and chlorfenapyr are pesticides for controlling tea green leafhoppers.However,registered dosages of three pesticides are very different,and the low pesticides utilization rate is a common problem in the use of pesticides.This paper discusses the digestion rules of three pesticides,the leaching rate in tea infusion and safety risks,clarifies the relationship between the dosage and control effects,studies and compares the pesticide deposits on tea trees of conventional?conical?spray and horizontal?fan?spray methods.The specific research results are as follows:1.Detection methods for the extraction of target pesticides in fresh tea leaves and dry tea with acetonitrile,florisil+GCB column solid phase extraction combined with dispersive solid phase extraction?PSA and GCB?,tea soup using 1%formic acid acetonitrile extraction,and mass spectrometry were established.At the addition levels of 0.005-2.000 mg kg^-1?fresh leaves?,0.005-2.000mg kg^-1?dry tea?and 0.01-0.5 mg kg^-1?tea brew?,the recovery rates of three pesticides are 70.3%-103.8%,RSD<20%,the limits of quantification in fresh leaves,dry tea and tea soup are 0.005 mg kg^-1,0.005 mg kg^-11 and 0.002 mg L^-1.2.Migration and safety evaluation of bifenthrin,indoxacarb,and chlorfenapyr during planting,processing and brewing.Dissipations of three pesticides conformed to the first-order kinetic equation,and the half-lives of bifenthrin,indoxacarb and chlorfenapyr were 1.1-4.5 d,1.4-2.1 d and2.3-4.8 d,respectively,they were pesticides that dissolved fast.The overall degradation rates of bifenthrin,indoxacarb and chlorfenapyr were 42.2%-57.4%,36.4%-48.1%and 59.1%-67.6%.The total leaching rates of bifenthrin,indoxacarb and chlorfenapyr in three infusions were 0.17%-0.24%,5.73%-6.91%and 2.68%-2.70%,respectively.The evaluation results of the risk quotient?RQ?method showed that RQ values of three pesticides were far less than 1,which meant that risks of dietary intake of these three pesticides through drinking tea were extremely low.3.Distribution of pesticides in bifenthrin,indoxacarb and chlorfenapyr on tea plants and control effect on tea green leafhopper.Control effects of chlorfenapyr and indoxacarb on tea green leafhoppers are higher than bifenthrin.Bifenthrin was poorly controlled against tea green leafhoppers in three areas,Shengzhou City,Zhejiang Province,Fu'an City,Fujian Province,and Meitan County,Guizhou Province;indoxacarb had good control effects in 3 days overall,when the effective dose was56 g ai/hm²,the control effect was 72.6%-79.1%after 3 days,and the control effect decreased in Zhejiang and Fujian after 7 and 14 days;chlorfenapyr showed good control effect in three places,and the effective dose was 72 and 108 g ai/hm².4.The effect of conventional?conical?spray and horizontal?fan-shaped?spray on the amount of pesticides deposited on tea trees.Pesticides are mainly deposited in the upper and middle layers of tea trees,accounting for 75.4%-98.9%of the total deposition;The horizontal spray method of fan-shaped spray nozzle is more conducive to the slight attachment of pesticides on tea leaves.The deposition of pesticides in the upper leaves is 1.4-1.8 times that of cone sprays;the deposition on the front of the leaves is increased by 6.2%-67.8%compared with cone sprays,The reverse side of the blade increased by 24.5%-67.9%.