Abstract: The extract of toosendanin from the traditional Chinese medicine of the Melia genus can be formulated as an agricultural insecticide. To verify its safety, the residual digestion dynamics and final residues of 0.3% toosendanin pesticide-SL in cabbage and soil were measured in this study. According to dynamic study on residue digestion, twice the recommended dose of 7.5g a.i./hm² was sprayed once to cabbage and soil, and the residual amount of toosendanin in the samples was detected by IC-ELISA and HPLC, respectively. It was found that the degradation process was in line with the first-order kinetic mathematical model. The half-life of toosendanin in cabbage was 1.2 d and 1.6 d, respectively, and in soil, 0.71 d. The final residue test showed that, when the recommended doses of 3.75g a.i./hm² and 7.5g a.i./hm² were sprayed with water for 3 to 4 times at an interval of 7 d, the final residue of toosendanin detected by IC-ELISA was 0.009 mg/kg and 0.015 mg/kg, respectively, at 7 days after the last application. No toosendanin was detected by HPLC. No residue of toosendanin was detected in the soil by either method. The results show that 0.3% toosendanin pesticide-SL is a new safe type of plant-based pesticide, which is easily degraded and relatively safe for release into the environment.

Key words: toosendanin, 0.3% toosendanin pesticide-SL, cabbage, soil, degradation dynamics