The synergism of chlorfluazuron and alphacypermethrin against Plutella xyllostella L. was measured with immerge leafs method, and the best ratio was confirmed.

• 采用浸叶法测定了定虫隆与高效氯氰菊酯混配后对防治小菜蛾3龄幼虫的增效作用及两种药剂混配的最佳配比。