Pyrethrum: the natural insecticide

Pyrethrum is a highly effective insecticide which has been used for centuries against all manner of insect pests. With an excellent environmental and toxicological profile, fast acting, and in ready supply, pyrethrum is the insecticide of the 21^st Century.

What is pyrethrum?

Pyrethrum is a natural plant oil that occurs in the pyrethrum daisy, Tanacetum cinerariaefolium, a member of the chrysanthemum family. It is found mainly in tiny oil-containing glands on the surface of the seed case in the tightly packed flower head and is the plant’s own insecticide that has evolved to keep insects away. Pyrethrum is made up of six complex chemical esters known as pyrethrins which work in combination to repel and kill insects. Pyrethrum is a unique insecticide in that, used correctly, it is relatively non toxic to humans and warm blooded animals. It also breaks down quickly in sunlight and is non-persistent in the environment. Because pyrethrins are such complex and non-persistent chemicals, insect resistance is less likely to occur.

How does it work?

Pyrethrum affects the central nervous systems of all types of flying and crawling insects, blocking nerve junctions so that nervous impulses fail, and the insect dies. In the lowest concentrations, pyrethrum affects insect behaviour producing a so called ‘avoidance reaction’ which results in the insect fleeing the source of the chemicals. Importantly, pyrethrum, inhibits normal biting behaviour in female mosquitoes, making them unable to seek their usual blood meals. At slightly greater concentrations, pyrethrum makes insects lose usual behavioural patterns. This means they abandon their hiding places and come out into the open, bringing them into contact with larger quantities of pyrethrins which soon knock them down and kill them.

Pyrethrum in history

Pyrethrum has been tried and tested over centuries. The pyrethrum daisy is mentioned in early Chinese history, and it is thought that the plant was brought to Europe from China along the silk routes in ancient times.  Pyrethrum grew plentifully in Persia (Iran) and Dalmatia (Croatia) and in the 19^th Century, ground pyrethrum flowers were found in most European pharmacies. Pyrethrum powders were used by armies from the time of Napoleon to the Second World War to combat head and body lice. Before the World War II, Japan was the major growing area, but during and after that period, East Africa was the main pyrethrum producing area. For the past 15 years, the Australian island state of Tasmania has been home to the world’s most high-tech pyrethrum industry where innovative farming and extraction techniques have continually increased production, ensuring a stable supply of  the insecticide for the growing world market.

Growing and extraction

Pyrethrum is a perennial plant that can produce flowers for harvest for up to five years. The daisies are in full bloom in the southern hemisphere summer: December and January. The flowers are first cut and allowed to dry in the field. The flower heads are then brought in with specially adapted headers, are pelletised, and undergo extraction to produce a dark oleoresin. This oleoresin is then refined to produce and clear straw coloured liquid which is formulated to clients specifications and exported worldwide. It is these pyrethrins that are used in a great range of insect abatement products from sprays for large scale aerial use, to foggers, to aerosols for use in the home to mosquito coils for burning indoors and out.

Pyrethrum: effective, fast working, non-persistent. The natural alternative for use where safety really matters.