Study And Research Behaviors Of Residue In Citrus And Adsorption In Soil Of Thiophanate-Methyl And Pyraclostrobin

Citrus is an important economic crop in China,has been the first in the world after continuous development,but the yield has been the second largest in the world.Fungicide thiophanate-methyl and pyraclostrobin have certain control effect against anthracnose in the citrus,but it is easy to reduce the control effect to continuous and single using dose,leading to resistant bacteria.Compounding of thiophanate-methyl and pyraclostrobin is able to delay the produce of bacteria resistance of a single dose effectively.In order to evaluate the environment security of complex dispensing,to detect the residual status of the two kinds of pesticide in citrus and behavior in the soil environment,this study is aimed at establishing a determinationmethodof residual of thiophanate-methyl,carbendazim and pyraclostrobin..To establish a way to analyse residual quantity of pyraclostrobin?thiophanate-methy and carbendazim in citrus,metabolite of thiophanate-methy,then do research on their residual decomposition dynamics,and final residual quantity in citrus and soil,a dsorption rate and migration ratio in soil.The sample pretreatment was conducted by optimal QuEchERs,and the determination was conducted by UPLC-MS/MS and external standard method.When the mass concentration was 0.004⁴.0 mg·L^-1,the mass concentration and response value of Pyraclostrobin?thiophane-methy and carbendasim have a good linear relation.While the addictive concentration was 0.004¹.0 mg·L^-1,the average recovery rate of them was82.5%¹17.9%,and the RSD was 1.3%¹0.7%.The LOD of Pyraclostrobin?thiophane-methy and carbendasim were 0.005?0.05 and 0.005 ng.The LOQ of Pyraclostrobin?thiophane-methy and carbendasim were 0.004?0.01 and 0.004 mg·kg^-1,The QuEchERs,high sensitivity,easy to handle and efficient,is accord with the standard of determination of pesticide residues.It is a study of thiophanate-methy and pyraclostrobin's half-life,final residues,adsorption constant K_f and migration constant R_f in citrus and in soil.The half-life of thiophane-methy and Pyraclostrobin in citrus were 2.8⁶.4 d and 3.9²1.0 d,which belongs to easily degradable pesticide.After 14 days,the final redidual quantity of them in citrus are0.121¹.059 mg·kg^-1,0.005⁰.659 mg·kg^-1,Pyraclostrobin is lower than the max standard residual quantity 1.0 mg·L^-1 in CAC,Thiophane-methy is lower than the max standard residual quantity 5.0 mg·L^-1 in our country.Based on the research of adsorption rate and migration rate two pesticides,lgK_f of the Pyraclostrobin is 0.55⁰.62,R_f of migration cons-tant is 0.23⁰.56,while lgK_f of thiophanate-methy is 0.47⁰.71,R_f of migration is 0.33⁰.72.In the same soil,pyraclostrobin's absorption capacity is higher than that of thiophanate-methy,while migration rate is lower than thiophanate-methy.In different soil,pyraclostrobin and thiophanate-methy have high absorbed ability,low migration rate when organic content high.When using 45%pyraclostrobin and thiophanate-methyl suspending agent of citrus anthracnose,the highest dose of effective components for prevention and cure is 450⁶75mg/kg,up to 3 times,applying pesticide spray interval is 10 days,and citrus harvest security interval 14 days.The mobility to thiophanate-methyl is positive when the soil organic matter content is 17.5%.Take propper isolation measures when applying pesticide,and be careful when using around life water areas.