40%毒死蜱乳油在桑园使用后对家蚕的影响评估

采用食下毒叶法测定及气相色谱分析,研究了40%毒死蜱乳油对家蚕的急性毒性、桑园使用后在桑叶中的残留消解动态及桑叶中残留农药对家蚕的急性毒性和亚致死效应。结果表明:按有效成分计,40%毒死蜱乳油对家蚕的急性毒性LC50值为0.82 mg／kg(桑叶),对家蚕为高毒;以推荐剂量(1 500倍稀释液)和1.5倍剂量(1 000倍稀释液)在桑园使用后,1.5倍剂量下40%毒死 蜱乳油在桑叶中的降解半衰期为1.82~3.88 d,第22 d时其在桑叶中的残留量为0.01~0.28 mg／kg; 推荐剂量下第18 d时的最终残留量为低于LOD~0.20 mg／kg。当桑叶染毒剂量为0.56 mg／kg时,对家蚕不会产生急性毒性危害,桑叶染毒剂量小于0.20 mg／kg时,与空白对照相比,处理组家蚕眠蚕体重、死笼率、全茧重、茧层率不存在明显差异。为防止施用毒死蜱乳油对家蚕产生危害,建议该农药在桑园中使用次数为1次、 喷雾使用1 500倍稀释液时,安全间隔期至少应为18 d。

Effect of 40% Chlorpyrifos Emulsifiable Concentratesto Silkworm with Spraying Application in Mulberry Field

Acute toxicity to silkworm (Bombyx mori L.) caused by chlorpyrifos was tested.Residue dynamic of chlorpyrifos was determined on mulberry leaf sprayed with 40% chlorpyrifos EC diluted by 1 000 or 1 500 times with water.The acute toxicity and sub-lethal effect caused by the chlorpyrifos residues to silkworms was also investigated.As a result,the 96 h LC50 of chlorpyrifos to silkworms was 0.82 mg／kg of mulberry leaf with feeding method.According to the toxicity category,the acute toxicity of chlorpyrifos to silkworm belongs to the high class.The results also showed that when applied in a rate of high dose,the short half-life of the dissipation rate of chlorpyrifos in mulberry leaves was 1.82 ~3.88 d.At the 22nd day after the application,the residue of chlorpyrifos was 0.01 ~0.28 mg／kg in mulberry leaf.When applied with chlorpyrifos diluted by 1 500 times,the residue was found to be at the level of LOD ~0.20 mg／kg of mulberry leaf at the 18th day.When feeding with the dose of 0.56 mg／kg of mulberry leaf,the silkworms showed no observed effect.When feeding with a dose lower than 0.20 mg／kg of mulberry leaf,the mortality,larval weight,cocoon weight and cocoon shell ratio did not decrease significantly as compared with that of the control treatment.In conclusion,in order to prevent the harmful effects to silkworms,the application of 40% chlorpyrifos EC diluted by 1 500 times within one application in the whole season was recommended with pre-harvest interval of 18 days as the GAP.