pyrethrin

例句：

1. 1.This insecticide is made from the pyrethrins found in chrysanthemum flowers.
   这种杀虫剂是用菊科植物中的除虫菊素制成的。
2. 2. The farmers used to use pyrethrin as a natural pest control method.
   农民过去使用除虫菊素作为天然的害虫控制方法。
3. 3.Insects are sensitive to pyrethrin and will not survive long after exposure.
   昆虫对除虫菊素敏感，接触后存活时间不长。