Residue Dynamics Of Botanical 0.5%Toosendanin Pesticide-EC In Cabbage And Tobacco Field Ecosystem

Toosendanin (TSN) is a triterpeniod extracted from Melai toosendan Sieb. et Zucc.which was used as a digestive tract parasiticide and agricultural insecticide in ancient China.It has a wide range of pharmacological and insecticidal activity,especially for pest control on crops. Toosendanin-based botanical pesticides,such as 0.5% toosendanin pesticide-EC,the pesticide have a high control effect to the chewing mouthparts pests of vegetables, fruit, tea, tobacco, flowers and other economic crops.Residues analytical methods of Toosendanin in cabbage and tobacco field ecosystem were established. The detection methods are including IC-ELISA and HPLC.Dissipation and the terminal residues of Toosendanin in cabbage,tobacco and soil were studied in this paper.This study not only provides a theoretical basis for the registration and promotion of 0.5% toosendanin pesticide-EC but also the scientific basis for the safe and rational use of guidelines and development of maximum residue limits. The main conclusions are as follows:1) An indirect competitive enzyme-linked immunosorbent assay (IC-ELISA) on TSN in tobacco,cabbage and soil were established. The minimum detection limit of the toosendanin was 0.004 ug/mL。The established quantitative determination method was available with 94.3%¹04% average recoveries of toosendanin residue in tobacco, 78%¹10% in cabbage, 75.4%¹03.5% in soil,with the corresponding RSD of 4.1%⁷.4%,3.9%⁷.0% and 2.3%⁸%, respectively.2) Residue analysis methods of TSN were established in tobacco,cabbage and soil. The sample was determined by HPLC-UV. The limits of quantitation of TSN in tobacco,cabbage and soil were 0.02 mg/Kg, 0.02 mg/Kg and 0.01 mg/Kg, respectively. the average recoveries in tobacco,cabbage and soil were 89.2%⁹7.9%,78%⁹4 % and 91.9%⁹6.7%,with the relative standard deviations were 4.0%¹1.9%,1.6%⁹.4 % and 3.5%⁵.3%.3) Degradation dynamic of 0.5% toosendanin pesticide-EC in tobacco,cabbage and soil was studied in Shanxi. The tobacco,cabbage and soil were treated with the pesticides at two times of the recommendation dosage. Samples of tobacco,cabbage and soil were analysised at different time, then the degradation procedure was corresponding to the mathematic pattern: C_t=C₀e^-kt. The half lifes of TSN in tobacco,cabbage and soil were 1.5-2.1d,1.2-1.6d and 0.71d,respectively. The result showed that TSN was degraded easily in tobacco,cabbage and soil.4) With sprayed 0.5% toosendanin pesticide-EC in tobacco,cabbage and soil at recommended dosage and two times of the recommendation dosage by a one-year in Shaanxi. On the 7th day after the last application, the final residue of TSN in tobacco,cabbage was≤0.081 mg/Kg and≤0.015 mg/Kg and in soil was not detected.