桑树喷施65%毒死蜱乳油后药剂的残留动态及养蚕安全间隔期

Residual Dynamics of Chlorpyrifos After Spraying on Mulberry Trees and the Safety Time Interval to Silkworm

65%毒死蜱乳油是防治桑螟等害虫的桑树专用有机磷杀虫剂。于春、秋2季分别以325 mg/L、650 mg/L毒死蜱药液1次或2次喷施桑树后,采用气相色谱检测技术定量分析药物在桑叶和桑园土壤中的残留动态变化,建立药物降解曲线方程,用于预测施药后能确保蚕作安全的间隔时间。检测桑叶中药物的降解过程：施药后7 d内药物降解速度较快,以施药后1 d内最快,期间不同浓度药液及施药次数处理组间样品检测值差异较大;施药7 d后,样品检测值趋于稳定,且2次施药处理的药剂残留始终高于1次施药处理,而施药浓度与药剂残留量的关系不大,多次施药后药物残留有累积作用。检测土壤中药物的残留量低于同期以相同浓度药液处理后在桑叶中的残留量,1次施药的残留量低于2次施药的残留量,但秋季施药14 d后,药物在土壤中的降解则更加缓慢。采用650 mg/L毒死蜱药液喷施1次和2次后的检测数据,建立了药物在桑叶及桑园土壤中的降解曲线方程,用于测算毒死蜱药液喷施桑树后桑叶中药物残留量〈0.5 mg/kg时的家蚕安全饲养间隔期：春季1次施药为16-18 d,2次施药为22 d;秋季1次施药为25 d,2次施药为30 d。

65% chlorpyrifos emulsifiable solution（ EC） is a kind of organophosphorus pesticide specially for controlling mulberry pests including Diaphania pyloalis. The residual dynamics of chlorpyrifos in mulberry leaf and mulberry field soil were investigated by means of gas chromatography after spraying 325 mg / L and 650 mg / L chlorpyrifos onto mulberry trees for 1 and 2 times in spring and autumn. And the degradation dynamic equation of chlorpyrifos was established to calculate the safe interval periods for silkworm breeding after spraying. Determination results of chlorpyrifos in mulberry leaves showed that the degradation rate of chlorpyrifos was high within 7 days and reached the highest value at day 1after spraying. In this period（ at day 1 to day 7 after spraying）,the detected residue value of chlorpyrifos in mulberry leaf sample was greatly varied with different pesticide concentrations and spraying times. After 7 days,the detected value maintained relatively stable,and the pesticide residue in mulberry leaf sample after spraying for 2 times was alwayshigher than that in mulberry leaf sample after spraying for 1time. No obvious relationship was observed between pesticide concentration and residue. There was cumulative effect when the pesticide was used repeatedly. The pesticide residue in soil sample was lower than that in mulberryleaf sample after spraying with the same concentration of chlorpyrifos at the same time. The pesticide residue in soil sample after spraying for 1 time was lower than that in soil sample after spraying for 2 times. The degradation rate of chlorpyrifos in mulberry field soil was lowered at day 14 after spraying in autumn. On the basis of detected residue value of chlorpyrifos in mulberry leaf and soil after spraying 650 mg / L chlorpyrifos for 1 and 2 times,the degradation curves were obtained. According to the degradation dynamic equations,the safe interval periods for silkworm breeding（ when chlorpyrifos residues in mulberry leaf 0. 5 mg / kg） was calculated to be 16- 18 and 22 days after spraying 1 and 2 times in spring respectively and to be 25 and 30 days after spraying 1 and 2 times in autunm respectively.