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Pyrethrum refers to several Old World plants of the genus Chrysanthemum (e.g., C. coccineum) which are cultivated as ornamentals for their showy flower heads. It is also the name of a natural insecticide made from the dried flower heads of C. cinerariifolium and C. coccineum. Pyrethrum was used for centuries as an insecticide[1] and as a lice remedy ("Persian Insect Powder," "Persian Pellitory") in the Middle East. It was sold worldwide under the brand Zacherlin by Austrian industrialist J. Zacherl.[2]

Some members of Chrysanthemum, including these two, are placed in another genus, Tanacetum, by some authorities. Both genera are members of the daisy (or aster) family, Asteraceae. They are perennial plants with a daisy-like appearance and white petals.

  • C. cinerariifolium is called the Dalmatian chrysanthemum, denoting its origin in that region of the Balkans (Dalmatia). It looks more like the common daisy than other pyrethrums. Its flowers, typically white with a yellow center, grow from numerous fairly rigid stems. Plants have blue-green leaves and grow to between 45 to 60 cm in height. The plant is economically important as a natural source of insecticide. The flowers are pulverized and the active components called pyrethrins, contained in the seed cases, are extracted and sold in the form of an oleoresin. This is applied as a suspension in water or oil, or as a powder. Pyrethrins attack the nervous systems of all insects, and inhibit female mosquitoes from biting. When not present in amounts fatal to insects, they still appear to have an insect repellent effect. They are harmful to fish, but are far less toxic to mammals and birds than many synthetic insecticides and are non-persistent, being biodegradable and also breaking down easily on exposure to light. They are considered to be amongst the safest insecticides for use around food. Kenya produced 90% (over 6,000 tonnes) of the world's pyrethrum in 1998, called py for short. Production in Tanzania and Ecuador is also significant.
  • C. coccineum, the Persian chrysanthemum, is native to Caucasus and looks somewhat like a daisy. It produces large white, pink or red flowers. The leaves resemble those of ferns, and the plant grows to between 30 and 60 cm in height. The flowering period is June to July in temperate climates (Northern hemisphere). C. coccineum also contains insecticidal pyrethrum substances but it is a poor source compared to C. cinerariifolium.
  • Other species such as C. balsamita and C. marshalli also contain insecticidal substances, but are less effective than the two species mentioned above.
  • Pyrethroids are synthetic insecticides based on natural pyrethrum (pyrethrins); one common example is permethrin. A common formulation of pyrethrin is in preparations containing the synthetic chemical piperonyl butoxide: this has the effect of enhancing the toxicity to insects and speeding the effects when compared with pyrethrins used alone. These formulations are known as synergized pyrethrins.

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Companion planting

Because of the natural insecticidal properties of the pyrethrums, they are used as companion plants, to repel pest insects from nearby crops. One might, for instance, plant them among broccoli plants in order to protect them from any of several insect pests. They are thought to repel aphids, leafhoppers, spider mites, harlequin bugs, ticks, pickleworms and imported cabbage worms, among others that are in gardening.

Common names

Common names for Chrysanthemum cinerariaefolium include:

  • Pyrethrum
  • Pyrethrum daisy
  • Dalmatian pyrethrum
  • Dalmatian chrysanthemum
  • Dalmatian Insect Flower
  • Dalmatian pellitory

Common names for Chrysanthemum coccineum include:

  • Pyrethrum
  • Pyrethrum daisy
  • Painted daisy
  • Persian chrysanthemum
  • Persian Insect Flower
  • Persian pellitory
  • Caucasian Insect Powder Plant

See also

Notes

  1. ^ Bioaromatica The history of pyrethrum
  2. ^ US308,172 (PDF version) (1884-11-18) Johann Zacherl, Pyrethrum Soap.  

External links


1911 encyclopedia

Up to date as of January 14, 2010

From LoveToKnow 1911

PYRETHRUM. The pyrethrum or "feverfew" (nat. ord. Compositae), now regarded as a section of the genus Chrysanthemum, flowers in the early summer months, and is remarkable for its neat habit and the great variety of character and colour which it presents. The type form is the Caucasian species roseum of botanists, hardy perennial, with finely cut leaves and large flower heads, having a ray of deep rosecoloured ligulate florets surrounding the yellow centre or disk. They bloom during the months of May and June, as well as later, and are always most welcome ornaments for the flower borders, and useful for cutting for decorative purposes. There are now many excellent varieties, both single and double-flowered, in cultivation.

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. The plants may be increased by division, the side shoots being taken off early in spring rather than in autumn, with a portion of roots attached. Plants disturbed in autumn frequently die during the winter. They may be placed either in separate beds or in the mixed flower border as may be required. In beds they can be supplemented as the season passes on by the intermixture of later blooming subjects, such as gladioli. Slugs are often destructive to the young shoots, but may be checked by a few sprinklings of soot or lime. Seeds should be sown in spring in a cold frame, and the young plants should be put out into beds when large enough, and should flower the following May. New varieties are being constantly introduced; the reader is referred to the catalogues of nurserymen for named kinds. The powdered root of P. roseum and other species is used in the manufacture of insect powders.

P. parthenifolium var. aurem is the "golden-feather" of gardens, so much employed as an edging to flower-beds. P. parthenium, pellitory or "feverfew," was formerly used in medicine. Its double-flowered form is well worth growing. P. uliginosum is the "great ox-eye daisy" that flowers in September and October.


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