Degradation Dynamics of Chlorpyrifos in Mulberry Leaf and Soil and Safety Interval for Silkworm
ZHENG Jun-yao;SHEN Lan-lan;WANG Meng-cen;LIU Xun-yue;WU Hui-ming;Zhejiang Agriculture and forestry University School of Agricutural and Food Science;Institute of Pesticide and Environmental Toxicology, Zhejiang University;
[Aims] Degradation dynamics of chloryrifos in mulberry leaf and soil were investigated to evaluate the safety of application of chloryrifos on mulberry. The degradation dynamic equation of chlorpyrifos was established to calculate the safe interval period for silkworm. [Methods] The chlorprifos was applied at the rates of 1500 mg a.i./L and1 mL/m~2. The residual dynamics of chlorprifos in mulberry leaf and soil were investigated by gas chromatography, and the degradation dynamic equation of chlorpyrifos was established. [Results] The half life of choepyrifos was 1.9- 4.0 d in leaf and 8.4- 9.4 d in soil. According to the degradation dynamic equations, when chlorpyrifos residue in mulberry leaf was 0.2 mg/kg, the safe interval period for silkworm in Zhejiang and Guangzhou Province were 35 and 18 d,respectively. [Conclusions] Degradation of chlorpyrifos is fast in mulberry leaf and soil, and the degradation rate was influenced by environmental condition. Therefore, determination of safe interval period for silkworm should be base on the environmental conditions of the experimental field.