Pyrèthre

The pyrèthre or pyrèthre of Dalmatie ( Tanacetum cinerariifolium ) is a long-lived Plante herbaceous of the family of the Asteraceae (Made up), cultivated for its flowers from which one draws a powder Insecticide.

Vernacular names: pyrèthre, pyrèthre of Dalmatie, insecticidal chrysanthemum

Description

Hardy perennial from 40 to 60 cm in height, pushing in tufts with many stems carrying each one a capitulates final. All the plant is covered with soft and cottony hairs.

Pennatiséquées sheets glaucous green.

Flowers grouped in flowerheads 4 cm in diameter to yellow central disc and white peripheral ligulas. The receptacle convex and is surrounded by a cottony involucre. The central flowers (yellow florets tubuliflores) are hermaphrodites and comprise 5 anthères brought together in a tube crossed by the style. The ligulées flowers have a corolla in white strip finished by three teeth and are only female, cheesecloths being transformed into staminodes.

The fruit is a Akène which does not carry a brush.

Distribution

The pyrèthre of Dalmatie is a species originating in the south-east of Europe (Croatia, Montenegro, Albania). It was largely spread by the culture, in particular in Europe (Italy, Spain), with the Japan, in North Africa, in Kenya, in Rwanda (plantations with the detriment of the National park of Virunga sheltering gorillas).

Properties

The plant has a certain economic importance like source of natural Insecticide. The flowers are pulverized, and one extracts from them the active components, a group of Ester S called Pyréthrine S (C21H28O3, or C22H28O5) contents in various fabrics but mainly in the flowerheads, which are sold in the form of oleoresins. The application is done in the form of suspension in water or oil, or in the form of powder. Pyrethrins tackle the nervous system of all the insects, and inhibit the mosquitos females by empéchant them to prick. With amount lower than the fatal threshold with the insects, they always have an effect Répulsif. They are active against fish, but much less toxic for the mammals and the birds that many insecticides of synthesis, and are not persistent because they are biodegradable and break up easily by exposure to the light. It is considered that they are insecticides among surest for a use in the food field.

The Kenya is the first world producer of pyrèthre, but the Tanzania increases its production.

Production

Synonyms

Chrysanthemum cinerariifolium (Trevir.) Screw.
Pyrethrum cinerariifolium Trevir.

External bonds

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