Pyrethrum and Permethrin Insecticides
-- Natural pyrethrum versus synthetic permethrin insecticides --
Summary: There is a lot of confusion over the terms permethrin and pyrethrum. Permethrin is a man-made synthetic insecticide whose chemistry is based on natural pyrethrum compounds that are derived from the flowers of the chrysanthemum plant. Said another way, permethrin is a synthetic insecticide based on the chemical structure of a natural plant compound called pyrethrum**. This article examines the important differences between these similarly named materials.
**Pyrethrum is also the generic name for some chrysanthemum plant species.
Natural Pyrethrum Insecticide
Pyrethrum is a crude extract made from dried and ground chrysanthemum flowers. The dried powder is sometimes called "insect powder". Crude pyrethrum is composed of several (as many as six) compounds called pyrethrins ("pie-wreath-rins") including pyrethrin I and cinerin I and others that are refined from the crude pyrethrum extract. Today, natural pyrethrins are widely used in household insect sprays, sometimes combined with another chemical called piperonyl butoxide (PBO) that enhances the effectiveness of the pyrethrins.
Brief history of "insect powder"
About 200 years ago people in central Asia discovered that dried, crushed flowers of certain chrysanthemum plants were toxic to insects. During the Napoleonic Wars (1804-1815) this "insect powder" was used to control flea and body lice infestations of French soldiers. Since then, pyrethrum has been used in many forms for effective, low toxicity insect control. However, because natural pyrethrum is not stable in sunlight it is seldom used today in commercial agriculture.
Using natural pyrethrins in home gardens
Pyrethrin insecticides, either alone or in combination with other compounds, are very effective, safe and environmentally friendly garden insecticides. They are very effective against a wide array of garden pests and can often be used right up to the day of harvest (see specific label instructions).
Pyrethrins are also botanical insecticides and are often combined with neem oil or insecticidal soap to make a highly effective, wide spectrum, low toxicity spray. These combination products can be used for aphids, scale insects, spider mites, thrips and many other leaf-feeding garden pests. Pyrethrin-based garden insecticides ("natural bug sprays") and other least-toxic garden pesticides are available here (DoMyOwn.com, one of our affiliates).
So what is permethrin insecticide?
Permethrin ("per-meth-rin"), on the other hand, is a synthetic (manufactured) insecticide, whose chemical structure is based on natural pyrethrins. It is one of hundreds of different pyrethroid insecticides. These insecticides were developed to match or exceed the effectiveness of natural pyrethrum but be more stable in sunlight. Pyrethroid insecticides are widely used in modern agriculture because of their stability in sunlight and high toxicity to insects.
Permethrin, one of the first pyrethroid insecticides, has recently seen an upswing in homeowner popularity since diazinon was taken off the US market. Permethrin has many uses from landscape pest control to head lice shampoos, flea, tick and mosquito control on dogs, and mosquito control on outdoor clothing and camping gear. Permethrin is relatively low toxicity but highly toxic to cats and some other animals.
Is natural pyrethrum a pyrethroid?
No. Pyrethrum is a relatively low toxicity natural insecticide (comprised of several different pyrethrins) and since it breaks down quickly, generally has low environmental impact as well. For these reasons it enjoys a reputation of being "safe". Pyrethroid insecticides, on the other hand, are generally more toxic, more environmentally persistent and therefore not as "safe". Unfortunately, some marketers continue to claim that pyrethroid insecticides like permethrin are "made from chrysanthemum flowers" implying that they are "natural and safe". These claims are false, and if done intentionally to mislead consumers, the claims are highly unethical.
Supplies
Professional-level pest control supplies are generally not available in home and garden stores but can be found at DoMyOwn.com, our affiliate.
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