Pyrethrum is extracted from a type of chrysanthemum (Chrysanthemum cinerariifolium). It is a small, white ray-type flower with a yellow center. The seeds are crushed to extract the active ingredients. Pyrethrum is favored as a pesticide because it works fast and degrades quickly in the environment. Used properly it is considered very safe.
Insect Control for Plants
Pyrethrum will kill insects if it is concentrated enough. It works by first paralyzing the pest and then attacking its nervous system. If the application is weak, the insect may recover after being incapacitated for awhile. Synergists, such as natural oils, are often added to the pyrethrum. Together the two ingredients are more effective. Pyrethrum products are consistently used in organic farming. Sprays are also available for the home garden. They are effective against insects such as aphids, thrips, white flies and leaf-hoppers. It is safe to use on edible fruit and vegetable plants. Pyrethrum degrades quickly in sunlight, so it will need to be reapplied often.
Insect Control on Pets
In the right amounts, pyrethrum is not harmful to mammals or birds. However, it can be toxic to fish in concentrated amounts. Like other pesticides, it should not be used near water sources. Powders and liquids are available containing pyrethrum. They can be distributed around pet bedding, in kennels, or applied directly to lawn grasses. It will kill fleas that would likely hop onto your pets. Pyrethrum is a common ingredient in flea powders, pet shampoos and spot-on flea treatments. It is important to always use pyrethrum according to label instructions. Do not confuse pyrethrum with synthetic pyrethrins, which are much stronger. Cats do not process synthetic pyrethrins well and can easily be overdosed. They tolerate natural pyrethrum better.
Insect Control on Humans
Pyrethrum or pyrethrins are generally used in combination with a chemical called Piperonyl Butoxide for the control of insects on humans. They can be found in lice shampoos. Pyrethrum may also be found in products aimed at crab lice and scabies. Since these are short term applications, the human body can easily process them. Pyrethrum will also act as a mosquito repellent.
Household Insect Control
Pyrethrum sprays can be used to control flying insects such as moths, house flies, gnats and mosquitoes in the home. They are also effective against crawling and hopping insects such as fleas, bed bugs, roaches, silver fish and ants. A powder form can be applied to carpets or along cracks where insects have been known to enter the home.