Pyrethrum is a botanical insecticide produced primarily in the flowers of Tanacetum cinerariaefolium, a species of the chrysanthemum plant family. Pyrethrum plants have historically been grown in commercial quantities in Kenya, Tanzania, Rwanda and Papua New Guinea. Over the past decade, Tasmania and Uganda began producing pyrethrum. Today Kenya and Tasmania are the largest pyrethrum growing and producing countries.
In East Africa the mature pyrethrum flowers are picked by hand, sun dried to remove moisture, and sent to a processing plant for extraction of the active ingredient-pyrethrins, a mixture of six closely related esters. In Tasmania the flowers have been bred to synchronously flower so they can be mechanically harvested. As in Africa, the flowers are sun dried and processed to produce the insecticide pyrethrum.
Pyrethrum is an ancient insecticide. The insecticide properties of the flowers were documented in the early 1800’s but it is suspected that the flowers were used to kill insects a considerable time earlier. The first commercially available products were powders made from ground flowers and later crude oil extractions became popular. Today, the refining of crude pyrethrum extract to remove the plant material, waxes, etc. is a highly complex process resulting in a product that is clear and free of allergens.
Pyrethrum has been used effectively to control insects for decades and is non-persistent, decomposing rapidly in the environment. This rapid degradation of pyrethrum has resulted in little known cases of insect resistance making it an excellent choice for the control of agricultural pests.
From a toxicological viewpoint, pyrethrum has been extensively studied. It is low in acute toxicity to man and other vertebrate animals, is non–carcinogenic, causes no adverse reproductive affects and is non-mutagenic.