Pyrethrum definition

pī-rēthrəm, -rĕthrəm
An insecticide made from the dried flower heads of any of these plants.
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A Eurasian perennial plant (Tanacetum coccineum) in the composite family, cultivated for its colorful flower heads and formerly used as a source of an insecticide.
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A closely related perennial plant (Tanacetum cinerariifolium), commercially cultivated as the source of an insecticide.
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A perennial plant (Chrysanthemum coccineum) of the composite family, widely grown for the white, pink, red, or purple flower heads.
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An insecticide made from the dried flower heads of several Old World chrysanthemums, esp. a species (Chrysanthemum cinerariaefolium) now grown extensively in the U.S.
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Any of several perennial African plants of the genus Tanacetum, especially Tanecetum cinerariifolium.
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(organic chemistry) Any of several insecticides obtained from these plants; pyrethrin.
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Other Word Forms

Noun

Singular:
pyrethrum
Plural:
pyrethrums

Origin of pyrethrum

  • Latin pellitory (Anacyclus pyrethrum) from Greek purethron from pūr fire (from its warming effect) pyretic

    From American Heritage Dictionary of the English Language, 5th Edition

Pyrethrum Sentence Examples

  • Pyrethrum cinerariaefolium is exported for the manufacture of insect-powder, and sunflowers are cultivated for the oil contained in their seeds.

  • The pyrethrum grows best in soil of a loamy texture; this should be well manured and deeply trenched up before planting, and should be mulched in the spring by a surface dressing of half-decayed manure.

  • Other prominent species are Campanula, Pyrethrum, aconite, Cephaelis, speedwell, Alchemilla sericea, Centaurea macrocephala, Primula grandis and a species of primrose.

  • They have a similar activity to the natural compound pyrethrum, which is extracted from plants of the Chrysanthemum family.

  • If they are completely infested, we feel that the only safe product to use is a pyrethrum based powder.

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Words near pyrethrum in the Dictionary