Pyrethrum

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Pyrethrum is an insecticide made from the flowers of various Tanacetum species. The main active ingredients are pyrethrins , as well as cinerins and jasmolines.

Tanacetum cinerariifolium

Manufacturing

Pyrethrum is obtained from the dried flowers of Tanacetum species by crushing or extraction with solvents . The powdered flowers used to come in various forms on the market. The only difference is the type of Tanacetum used as the starting material . The "Montenegrin and Dalmatian insect powder" is from the Dalmatian insect flower ( Tanacetum cinerariifolium , Syn. : Chrysanthemum cinerariifolium , pyrethrum cinerariifolium ), however, the "Armenian, Persian and Caucasian insect powders" from the Caucasian insect flower ( Tanacetum coccineum , Syn .: Chrysanthemum coccineum , Pyrethrum roseum , Pyrethrum carneum ).

Cultivation

In order to stimulate flower formation, the plants need cold nights with temperatures below 10 ° C. The commercial cultivation is therefore partly in regions with a temperate climate, e.g. B. in Europe, Japan, or Tasmania . In the tropics, high altitudes above 2000 m are also suitable for growing these plants. There they are mainly grown in Africa (including Tanzania, Kenya, Rwanda), South America (including Ecuador, Colombia) and New Guinea.

The plants are perennial. In Kenya, a pyrethrum plantation is typically used for three to four years. Around a ton of (dried) flowers are harvested there per hectare and year.

Economical meaning

The annual world production of dried pyrethrum flowers is around 20,000 t. About 500 t of a 50% pyrethrin extract can be produced from this. Sales were estimated at US $ 39 million.

While Kenya and Tanzania provided over 90% of the world's harvest in 1983, today around a third of the world's pyrethrum demand comes from Tasmania. The USA is the main customer.

The manufacturing cost of natural pyrethrum is high and the need for insecticides cannot be met by it alone. This led to the development of selective, highly effective compounds, so-called pyrethroids , based on pyrethrum , which were only suitable for widespread use in veterinary and crop protection.

effect

Pyrethrum acts as a contact poison that is neurotoxic to insects . The mechanism of action is based on preventing the voltage-dependent sodium channels in the axon membranes from closing again, preventing the nerve cells from rebuilding their resting membrane potential .

Pyrethrum is poisonous to all types of insects, including beneficial insects . It is also very toxic to fish. The LD 50 for pyrethrins in rats (male) orally is 2.14 g / kg, in female rats 0.7 g / kg, or more than 2 g / kg in the case of dermal absorption (through the skin). The MAK value in Switzerland was set at 5 mg m −3 (measured as inhalable dust ).

Pyrethrum decomposes rapidly under the action of daylight and thus loses its effectiveness.

use

The Romans already knew the effect of the extract. They called pyrethrum "Persian insect powder" and used it against lice and fleas.

In Germany, Austria and Switzerland pyrethrum itself is not as active ingredient in pesticides approved, but exist in all these countries approvals for purified pyrethrum, the pyrethrins. Their use is also permitted in organic farming .

In the domestic setting, pyrethrum is used

  • in so-called electric vaporizers against flies and mosquitoes
  • as insect sprays and strips against cockroaches, ants, etc.
  • as a remedy against fleas and animal fleas , flea collar for dogs
  • as a remedy against head lice ("Goldgeist forte", "Jacutin N Spray", "Infecto Pedicul")

Individual evidence

  1. ↑ a b A. Glynne-Jones: “Pyrethrum” (PDF; 274 kB), Pesticide Outlook - October 2001, pp. 195–198 (English).
  2. ^ Pyrethrum Oil (PDF Download Available). In: researchgate.net. ResearchGate, accessed October 3, 2017 .
  3. ↑ a b Pyrethrum Market Report 2017 - News, Size, Prices, Trends, Share, Growth and Forecast. In: co.uk. www.indexbox.co.uk, accessed October 3, 2017 .
  4. ↑ EPA: Reregistration Eligibility Decision for Pyrethrins. List B Case No. 2580 (PDF; 1.5 MB)
  5. ↑ Swiss Accident Insurance Fund (Suva): Limit values ​​- current MAK and BAT values , accessed on November 2, 2015.
  6. ^ Directorate-General for Health and Food Safety of the European Commission: Entry on pyrethrins in the EU pesticide database; Entry in the national registers of plant protection products in Switzerland , Austria and Germany ; accessed on March 12, 2016.

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