Resistance levels to the four insecticides in P.xylostellae varied during different seasons.In general, LC50 of the four insecticides were high in Autumn and low in Spring.

• 实验结果表明:不同季节四种农药亚致死剂量处理后,菜蛾绒茧蜂子代结茧率和羽化率与对照相比均有降低。