印楝素制剂（ＭａｒｇｏｓａｎＯ）对小菜蛾３龄幼虫具有较好的毒杀和生长发育抑制作用。小菜蛾３龄幼虫连续４ｄ饲喂经１５ｍｇ／Ｌ印楝素制剂处理的叶片时，幼虫和蛹死亡率达８４１２％；化蛹率、羽化率和正常羽化的雌虫生殖力随处理浓度升高而迅速下降；对多种杀虫剂产生抗性的小菜蛾田间品系和敏感品系的毒力无显著差异，其ＬＣ５０值分别为３６９０ｍｇ／Ｌ和２８７７ｍｇ／Ｌ Azadirachtin preparations (Margosan  O) on the 3rd instar larvae of Plutella xylostella has good toxicity and growth inhibition. The larvae and pupal mortality of the 3rd instar larvae of Plutella xylostella were 84.12% when fed with 15mg / L Azadirachtin for 4 days. The pupal rate, emergence rate and normal fecundity of fecundity were the highest with the treatment concentration The resistance of Plutella xylostella to various insecticides was no significant difference in the virulence, the LC50 values ​​were 3690 mg / L and 2877 mg / L, respectively