From Big Medical Encyclopedia

PYRETHRUM — the dried-up flowers of a camomile of the sort Chrysanthemum (Pyrethrum) containing pyrethrins — the substances having the expressed insecticidal properties.

The drugs prepared from P. are applied to destruction of arthropods — carriers of causative agents of diseases and ectoparasites of domestic animals. For P.'s production preferential dalmatsky camomile (sometimes the Caucasian camomile) which flower baskets collect during mass blossoming is used and dry up at a temperature up to 80 °. The insecticidal beginning of P. are 6 relatives on a chemical structure of substances; pyrethrins I and II, tsinerina of I and II and zhasmolina of I and II; mix them is called pyrethrins.

Pyrethrins — insecticides of contact action; they are highly effective concerning arthropods and a malotoksichna for hematothermal. At initial stages of action on insects pyrethrins stimulate their mobility, and then cause paralysis and death. Pyrethrins easily decay in the environment, especially on light and in the presence of oxygen, on non-toxic components. From P. prepare powder and extracts. Extract P. white spirit (flitsid) contains 0,06% of pyrethrins. The concentrated extracts P. containing 25% of pyrethrins are known, they are applied in the form of an aerosol to fight against the flying insects, and to extermination of not flying insects in a combination with the insecticides possessing the expressed residual action (e.g., with organophosphorous insecticides). The pyrethrins received from P. often are used in mix with so-called. Synergists (piperonilbutoksid, bukariolat, etc.) — the substances which do not have insecticidal properties, but strengthening toxic action of insecticides, including pyrethrins. Synergists render on P. as well stabilizing action.

Though pyrethrins of a malotoksichna for hematothermal, during the processing of rooms the drugs P. containing various fillers, solvents recommend to protect a respiratory organs (a respirator, a gauze bandage), to delete foodstuff from rooms, to air them after processing.

See also Pyrethroids .

Bibliography: Metcalf R. L. Organic insecticides, Their chemistry and mode of action, N. Y. — L., 1955.

Yu. P. Volkov.