Pyrethrum is a highly effective insecticide which both kills and repels
insects. Pyrethrum is a natural plant oil extracted from the
flowers of the chrysanthemum daisy
(chrysanthemum cinerariaefolium). The majority of the
pyrethrum produced in the world comes from the African countries of
Kenya, Tanzania, Rwanda and Ecuador. Other countries such as
Australia, Japan, Brazil and others produce smaller amounts.
Pyrethrum is an ancient insecticide. The
insecticide properties of the flowers were
documented in the early 1800ís 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. Mature
pyrethrum flowers are picked by hand, sun
dried to remove moisture, and sent to a
processing plantor extraction of crude
Crude pyrethrum contains 30 to 35 percent pyrethrins (insecticide) and about 50 percent impurities.
Pyrethrins are contact insecticides which affect the insect's nervous system. 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.
On the EPA Green List, Pyrethum is one of the least toxic
insecticides to mammals. Pyrethrum is biodegradable and breaks
down quickly in sunlight, air and water.
Pyrethrum and Piperonyl Butoxide:
Despite its safety and effectiveness,
natural pyrethrum does have certain limitations. Pyrethrum is
relatively expensive due to the costs of harvesting chrysanthemum
flowers (containing pyrethrum) by hand. Also, various insects such as the common housefly
can detoxify and recover from small amounts of pyrethrum. Natural
pyrethrum alone tends to break down quickly in the environment, rapidly
losing effectiveness after outdoor application. Research has
overcome the detoxification issue by combining pyrethrums with piperonyl
butoxide (PBO), a liquid synergist. PBO works by restricting an
enzyme that insects use to detoxify pyrethrum, allowing the insecticide
to be more effective.
Pyrethrum's qualities of rapid
degradation have also turned out to be a blessing in disguise.
Because it is biodegradable, Pyrethrum has been EPA registered and USDA
accepted for use in food processing facilities. Pyrethrum is
also applied to fruits and vegetables like tomatoes post harvest on the
way to market. Even though pyrethrins are nerve poisons, they
are not cholinesterase inhibitors like organophosphate or carbamate
insecticides. Pyrethrins are low in toxicity to mammals because
they are quickly broken down into inactive forms and pass from the body
in the urine and feces.
Pyrethrum has been trusted for decades in
both household and agricultural applications. New research has
found that pyrethrum, combined with a synergist, is one of the
fastest-acting insecticides available. Pyrethrum knocks down and
paralyzes insects before it kills. Upon exposure to pyrethrum,
insects are thrown into a state of nervous disorder and run or fly
around erratically. Hidden insects are flushed from their hiding
places and scuttle about until they contact lethal amounts of pyrethrum.
This response is due to the fact that the insect has lost control of its
central nervous system. These effects are collectively
referred to as activation.
Recent research has discovered that
Pyrethrum has a "jamming" effect on insects prior to activation.
Tests have shown that the biting female mosquito's food searching
mechanism, or "black box", can be jammed by trace amounts of pyrethrum.
An example test of the "jamming" phenomenon would be to fill glass cage
full of female mosquitoes and find some brave volunteers. Those
who place their arms into the cage can expect to receive up to 50 bites
per minute. Next, expose the mosquitoes to trace amounts of pyrethrum.
Then, those who place their arms into the cage receive no bites even
though the mosquitoes otherwise seem normal.
is another advantage to using pyrethrum. The reason is not fully
understood, but insects do not become resistant to the natural
insecticide. After decades of successful use, no insect population
has ever developed significant pyrethrum resistance. Intense study
of the pyrethrum molecule has led to the production of synthetic
pyrethroid insecticides. But, science has not yet devised a
synthetic insecticide that combines the speed, effectiveness, activation
effects and biodegradability of natural pyrethrum.