In order to study insecticidal activity of spinosad against Lymantria dispar, bioactivity and LC50 of spinosad against the 3rd and 5th instar larva of L. dispar and its effect on activities of the detoxifying enzymes were assayed in this study. The results showed that LC50 of spinosad in 24 h was 0.024 9 mg·L-1 against 3rd instar larva and 0.226 9 mg·L-1 against 5th instar larva. Spinosad had various effects on activities of the detoxifying enzymes under the LC50 treatment. Carboxylesterase (CarE) , glutathione-S-transferase ( GST) , multi - function oxidase ( MFO ) and alkaline phosphatase (ALP) were firstly significantly increased and then decreased (P < 0. 05 ) ; But for acid phosphatase (ACP) , the change pattern in activity were decreased - increased - decreased, and the variation was significant ( P < 0. 01 ) . The development duration of the larva treated with LC10 and LC50 of spinosad was not significantly different from control, but the larval survival rate and pupation rate were significantly lower than control (P < 0. 05 ). The result indicated that the biochemical indexes of L. dispar were affected by spinosad. Therefore, spinosad is a safe and effective pesticide for L. dispar.%为了研究多杀菌素对森林害虫舞毒蛾的杀虫活性,采用叶片药膜法测定多杀菌素对舞毒蛾3龄和5龄幼虫的生物活性及致死中量对其体内解毒酶活性的影响.结果表明:多杀菌素24 h致死中浓度(LC50)分别为0.0249 mg·L-1(3龄)和0.2269 mg·L-1(5龄)；致死中量多杀菌素对舞毒蛾3龄和5龄幼虫体内解毒酶存在不同程度的影响,其中对羧酸酯酶(CarE)、谷胱甘肽S-转移酶(GST)、多功能氧化酶(MFO)和碱性磷酸酯酶(ALP)大体上均表现为先激活后抑制作用,差异显著(P＜0.05)；而对酸性磷酸酯酶表现为抑制-激活-抑制作用,差异极显著(P＜0.01).LC10和LC50剂量的多杀菌素对舞毒蛾3龄幼虫的发育历期无显著影响,但能显著降低幼虫成活率及化蛹率(P＜0.05).多杀菌素对舞毒蛾有较强杀虫活性,能够有效影响舞毒蛾的生化指标,干扰其正常的生长发育,可以作为防治舞毒蛾的安全有效药剂.
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