Control Effect of Pymetrozine on Myzus persicae(Sulzer) and Analysis of its Residue in Tobacco Leaves

To improve the control effects of pymetrozine against Myzus persicae(Sulzer),the chemical was sprayed or irrigated to tobacco plants at the rate of 6 mg/plant during fast growing stage.The control effects were investigated on the 7th and 15th day after application,and pymetrozine residues in tobacco leaf were determined by HPLC in 1,2 and 4 weeks after application.The results showed that:spraying method was superior to irrigating method not only in control effect but also in persistence at the same dose.Although the residue level in the plants of spraying method was higher than that of irrigating method,it was far lower than the limits(1.00 mg/kg) recommended by CORESTA.The half-life of pymetrozine in leaf was 12 to 14 days.