Pyrethrins

Derived from Chrysanthemum species, pyrethrins are organic insecticides that highly toxic to both insects and fish. They will kill both harmful and beneficial insects. Pyrethrins are much less toxic to mammals, especially compared to most synthetic insecticides. They are fully biodegradeable, break down fairly quickly in light and heat, and as such should be applied in early evening.

Despite their overall safety, pyrethins can still have an irritant effect in humans. A correlation between pyrethrin use during pregnancy and autism has been found, though there is no proof that one actually caused the other. Still, organic does not always mean safe, and caution is advised.

Note that artificial analogues, so-called pyrethroids, which includes permethrin, are also used as insecticides. Pyrethrins may also be mixed with other synthetics: preparations may not be fully organic, or not at all.