Mosquito Systems - Bye Bye Bugs

Pyrethrum (Tanacetum Coccineum)

Introduction
Pyrethrum is one of the most important cash crops of Kenya, Africa.
It belongs to the family compositae. It is grown on small plots of approximately one to one and a half hectares of land. One may see pyrethrum in most of the small plots in Githunguri and Limuru divisions. Other pyrethrum producing areas include Kisii and Nakuru district.

Growing Conditions
Pyrethrum grows well in areas with fairly high rainfall of about 1000 to 1500 mm, dry spells during flowering and harvesting, warm temperatures moderated by altitude, best in high altitudes averaging 1,800 m above sea level. The soils should be rich volcanic and well drained – well limed soils are also ideal for growing of the crop. Harvesting is done by hand and thus the need for cheap labour.

Pyrethrum Growing in Kenya
Pyrethrum is grown in the Kenya Highlands of Nakuru, Laikipia, Kisii, Kiambu and Bomet.
The pyrethrum seeds are first cultivated in nurseries then transplanted to plots. They have to be kept weed-free. The maturity of the plant is approximately one year, therefore picking is done fortnightly and may go on for years.
Flowers are picked and dried under the sun or in oven burners. The flowers are bagged and transported to factories for processing. In the factory, the pyrethrum is crushed into powder and subsequently into active liquid form, containerized for export or local use.

Knockdown Effects
Because of its safety, pyrethrum has long been preferred for household and agricultural application. Recent research is revealing new power and new uses for this old and trusted insecticide. Combined with a synergist, natural pyrethrums are one of the fastest acting insecticides known. Even before it kills, it knocks down and paralyzes insects almost immediately. When it encounters pyrethrum, the insect is thrown into a state of nervous disorder. It runs from it's hiding place and scuttles around erratically, or adopts a confused flight pattern. Both responses show that the insect has lost all control of its central nervous system. This contact effect is called activation. Recent practice exploits the activation effect by adding small amounts of pyrethrum to a routine residual agricultural formulation. Pyrethrum activates hidden insects, driving them from Cover and into contact with the main insecticide. This "flushing" action has been most successful in the control of such hard to hit pests as the cotton bollworm and the gypsy moth.

Jamming
Recently, researchers have identified a subtle effect that occurs even before activation takes place, jamming. The jamming phenomenon suggests new uses for pyrethrum in the battle against malaria. To show how jamming works, you need only a cage full of voracious female mosquitoes and some extremely brave volunteers. Those who put their bare arms in the cage can expect to get some 20 to 50 bites per minute. But, if the cage is exposed to trace amounts of pyrethrum for only five minutes and the arm is then reinserted, no bites are recorded, even though the insects otherwise seem completely normal. Apparently small amounts of pyrethrum can jam the "black box" of the insect's food searching mechanism. The insects forget to eat, as it were. Because of this effect, low level pyrethrum applications have been shown to reduce the risk of malaria carried by indoor mosquitoes.

Resistance
There's more to pyrethrum's bag of tricks. The reason is not fully understood, but insects do not become resistant to natural pyrethrum. After decades of use, no insect population has ever developed significant pyrethrum resistance. Intense study of the pyrethrum molecule has produced the related synthetic materials, pyrethriods. But so far, science has not devised a synthetic that combines the speed, effectiveness, activation effects and biodegradability of natural pyrethrum.