【目的】 明确5种生物农药对二化螟Chilo suppressalis致死效应的生理生化机制。【方法】 本研究采用饲料混药法，测定了金龟子绿僵菌CQMa421、球孢白僵菌ZJU435、苏云金芽孢杆菌、乙基多杀菌素和阿维菌素5种生物农药对二化螟3龄幼虫的校正死亡率；经过药剂筛选，选择防效最佳的药剂对1~4龄幼虫进行毒力测定，并将药剂以LC₅₀的浓度处理3龄幼虫，探究了二化螟幼虫体内的总蛋白含量以及α-淀粉酶、蔗糖酶、海藻糖酶、胰蛋白酶、脂肪酶活性的动态变化。【结果】 在推荐剂量下，阿维菌素的毒力最强，处理4 d后的校正死亡率为97.78%，显著高于其他药剂（P < 0.05）；且1龄幼虫对阿维菌素最敏感，LC₅₀随龄期增加而升高。经阿维菌素（LC₅₀）处理后，可显著抑制幼虫蛋白质含量（P < 0.05），同时诱导α-淀粉酶、蔗糖酶、海藻糖酶、胰蛋白酶和脂肪酶这5种消化酶活性的显著升高（P < 0.05）。【结论】 阿维菌素对二化螟低龄幼虫具有很高的杀虫活性，以LC₅₀浓度处理后，幼虫体内的消化酶活性升高，导致其营养代谢失衡。该研究结果为阐明阿维菌素对二化螟的毒理机制提供了理论基础。

 [Aim]  To clarify the physiological and biochemical mechanisms responsible for the lethal effects of five biological pesticides on the rice stem borer, Chilo suppressalis. [Methods]  Corrected mortality rates of third instar C. suppressalis larvae after treatment with five biological pesticides, namely Metarhizium anisopliae CQMa421, Beauveria bassiana ZJU435, Bacillus thuringiensis, spinetoram and avermectin, were determined using the diet incorporation method. The toxicity of the most effective pesticide to different larval instars was then measured. Third instar larvae were treated with the LC₅₀ concentration of the pesticide, and dynamic changes in their total protein content, and in the activity of the digestive enzymes α-amylase, sucrase, trehalase, trypsin and lipase, were investigated. [Results]  Avermectin had the strongest toxicity at the recommended dosage, with a corrected mortality rate of 97.78% after 4 days. This was significantly higher than that of other pesticides (P<0.05). Moreover, first instar larvae were the most sensitive to abamectin; LC₅₀ increased with successive larval instars. Treatment with abamectin (LC₅₀) significantly reduced the protein content of larvae (P<0.05), and simultaneously abnormally elevated the activity of all five digestive enzymes monitored (P<0.05). [Conclusion]  Avermectin is highly toxic to young C. suppressalis larvae. Treatment with the LC₅₀ concentration of avermectin elevates the digestive enzyme activity of larvae leading to a nutritional, metabolic imbalance. These results clarify the toxicological mechanism underlying the effects of avermectin on C. suppressalis.