Study on the Residue and Degradation of Benfuracarb and its Ma in Metabolites in Cotton Field

The residue and degradat ion of benfuracarb and its main metabo lites were studied by gas chromatography, after 20% benfuracard EC had been applied to the cotton field. The results are as follows: (1)Benfuracarb could degrade to carbofuran rapidly in the cotton field so ils and cotton leaves. The h ighest residue of carbofuran in the cotton leaves came out in the same day of the insect icide applied, but the highest residue in the cotton field so il came out in the third day after the insecticide applied. It shows that the degradation rate of benfuracrb in the cotton leaves is faster than in the cotton field soil. (2)Carbofuran could degrade to 3-hydroxycarbofuran. The 3-hydroxycarbofuran’s residue levels in the cotton field soil and cotton leaves increase at first, and then decrease. Its highest residue came out in the 10th day, and clearly later than that of carbofuran. (3) The degradation of benfuracarb and carbofuran in cotton field soil and cotton leaves could be described with the equation: Ct= Co·e-kt, the half life of them 3.6～4.4 days in cotton leaves, and 10.4～11.9 days in the soil. (4)When 200～400 g/hm2 of benfuracarb (a. i) were app lied 20 days and 30 days before the harvest, the residue of benfuracarb ( included benfuracarb, carbofuran and 3-hydroxycarbofuran) was all less than 0.5 mg/kg in cotton-seed or in the tillage soil of cotton field.