Biochemical Effect & Characteristics

Pyrethrum is produced from the blossoms of Chysanthemum species. It is a mixture out of six different esters with the main component Pyrethrin 1. Pyrethrum is a contact poison, whereas for insects mainly the stigmas (breathing openings) act as entry portals. The nervous system of the insect body is disturbed by Pyrethrins, which first leads to a tremor and finally to the death of the animal.

To understand the molecular effect mechanism of Pyrethrum, the structure and the functionality of the nervous system has to be looked at first. Nerve cells are able to produce and forward electric signals by controlled ion flow in a targeted way. For that purpose voltage gated sodium channels in the cell membrane are opened for milliseconds, through which Na⁺ ions flow into the cell from outside. This short rise of positive charge in the cell is compensated again through channelling out Ka+ ions. Nevertheless, the short increase of charge is sufficient to activate neighbouring sodium channels in the membrane of the nerve cell, which again allows a short-term inflow of Na⁺. This way an electric stimulus transmission along the nerve cell is achieved.

There is no direct contact between two nerve cells so that an electric stimulus transmission is not possible. The stimulus transmission takes place chemically at the connection points of nerve cells, the synapses. If an electric signal reaches the end head of a nerve cell, neurotransmitters are poured out into the synaptic cleft between the nerve cells.

The neurotransmitters are binding to special receptors which lie in the membrane of the downstream cell. This causes the opening of sodium channels and an inflow of Na⁺ ions into the postsynaptic nerve cell. This again leads to the electric signal transmission through the effect described above. So this way the electric signal has overcome the connection of two nerve cells.

After the neurotransmitters have connected to the sodium receptors of the sodium channels in the synaptic cleft, they are inactivated rapidly by special enzymes and are absorbed again and recycled by the presynaptic cell.
Pyrethrins intervene the signal transduction by influencing the neurotransmitter caused opening of the sodium channels in the membrane of the postsynaptic cells. The molecular structure of the Pyrethrins allows the long lasting connection to the receptors and thus causes an enduring excitation of the nerve cells by a permanent uncontrolled inflow of Na⁺ ions into the cell. This causes the symptom tremor in the insects which leads to a quick death.

The Pyrethrum extract of Kenya Pyrethrum Information Centre is characterized by advantageous properties during application in the use against harmful insects.

High efficacy against a multitude of insects is achieved with the Pyrethrins in Pyrethrum extract. They have a strong neurotoxic effect as explained above, which leads to a fast knock down and death of the insects with an excellent flushing out effect. A development of resistances does practically not occur in free living insect populations.

Low environmental impact is another advantage of the natural extract out of the Chrysanthemum plant. When natural Pyrethrins are used, no significant risks arise because the substances contained do not show any persistence. The active substance is degraded quickly after application through UV light, air and humidity, so that no critical residues are developing in the environment or in treated goods.

Low human toxicity makes the active substance out of the Chrysanthemum plant particularly attractive because the application is very safe.