为了研究多杀菌素对黄褐天幕毛虫的杀虫活性及作用机制,采用叶片药膜法测定多杀菌素对黄褐天幕毛虫幼虫的毒杀效力,并用分光光度法检测LC50剂量药剂处理后不同时间点幼虫体内各种解毒酶和保护酶活性的变化。结果表明: 多杀菌素对4龄、5龄幼虫均表现出极高的杀虫活性,见效速度块; 而且黄褐天幕毛虫4龄、5龄幼虫经过多杀菌素处理后,谷胱甘肽S-转移酶均表现为复杂的抑制-激活-再抑制作用,多功能氧化酶活性则均表现为先抑制后激活的作用。多杀菌素对4龄幼虫羧酸酯酶活性具有激活作用,对乙酰胆碱酯酶和过氧化物酶均具有先激活后抑制作用,对超氧化物歧化酶具有先激活再抑制后激活的作用,对过氧化氢酶则表现为复杂的先抑制再激活后抑制作用。对5龄幼虫羧酸酯酶、乙酰胆碱酯酶、超氧化物歧化酶及过氧化物酶活性具有明显的抑制作用,而对过氧化氢酶则表现为先抑制再激活后抑制的作用。因此,多杀菌素能有效干扰昆虫解毒和保护系统,扰乱其正常的生理代谢,从而起到较好的毒杀效果。
To study the insecticidal activity and toxicity mechanism of spinosad,we assayed bioactivity of spinosad by leaf membrane method and its effects on the activities of detoxifying and protective enzymes in Malacosoma neustria testacea larvae by spectrophotometry. The results showed that spinosad had an extremely high toxicity against the 4th and 5th instar larvae. The glutathione S-transfer (GST) activity in 4 th and 5th instar larvae was firstly inhibited, then induced, and finally inhibited, while the mixed-functional oxidase (MFO) activity was inhibited and then enhanced. The induced effect on carboxylesterase (CarE), the induced and inhibited effect on acetylcholinesterase (AchE) and peroxidase (POD), and the complicated effects on superoxide dismutase (SOD) and Catalase (CAT) were determined in 4th instar larvae with spinosad treatment. However, the obvious inhibition effects were found on the activities of CarE, AchE, SOD and POD in the 5th instar larvae whereas the catalase (CAT) activity was inhibited, then increased, and inhibited finally. Therefore, spinosad could effectively disrupt and interfere not only the detoxifying and protective enzymes but also normal physiological metabolism of M. neustria testacea and show extremely high toxicity against this pest.