Study on Residue and Degradation of Deltamethrin in Oriental Tobacco

In order to assess the degradation behavior of deltamethrin residues in oriental tobacco,the field experiments were conducted for two consecutive years with 2.5% deltamethrin EC.The test results indicated that: 1) The degradation of deltamethrin EC in oriental tobacco accorded with first level dynamics degradation model,its half-life period was of 5.80 to 6.19 days.2) The residues of deltamethrin in oriental tobacco were below 0.0128 mg/kg 15 days after spraying,and the degradation rate was higher than 95%.3) The residues of deltamethrin in green leaf harvested on 15th day after spraying deltamethrin at a rate of 600 mL/ha(the recommended rate) for 2 or 3 times ranged from 0.01 to 0.4703 mg/kg.4) The degradation behavior was basically unchanged,though the climate conditions were different in the two years.It was concluded that the residues of deltamethrin in oriental tobacco would be below 0.05 mg/kg if it was repeated applied for 3 times at the recommended rate and at an interval of over 15 days.