by Seshata on 10/07/2013 | Uncategorized

Organic gardening 101: what is pyrethrum?

Pyrethrum is the name given to any one of several chrysanthemum species, as well as to the insecticidal preparation that can be extracted from two species, C. cinerariifolium and C. coccineum. Pyrethrum is directly toxic to several common cannabis pests including spider mite and aphid, and is remarkably non-toxic to mammals.


Pyrethrum is the name given to any one of several chrysanthemum species, as well as to the insecticidal preparation that can be extracted from two species, C. cinerariifolium and C. coccineum. Pyrethrum is directly toxic to several common cannabis pests including spider mite and aphid, and is remarkably non-toxic to mammals.

Taxonomy of pyrethrum plants

Somewhat confusingly, some botanists place the two species into a different genus, Tanacetum. However, both the Tanacetum and Chrysanthemum genera belong to the Asteraceae (daisy) family, and are comprised of very similar species.

Organic gardening 101 what is pyrethrum - 1 - Chrysanthemum cinerariifolium, the species that provides the bulk of the world's pyrethrum
Chrysanthemum cinerariifolium, the species that provides the bulk of the world’s pyrethrum

C. cinerariifolium (also known as T. cinerariifolium) is a sturdy perennial native to the Balkan region of Europe—a common name is the Dalmatian chrysanthemum, in reference to the Croatian coastline of the same name. Very similar in appearance to the common daisy, but with blue-green leaves and stalks growing up to one metre in height, C. cinerariifolium is produced in huge quantities by Kenya, Tanzania, Ecuador and Tasmania, Australia.

C. coccineum (or T. coccineum) is known as the Persian chrysanthemum, and is indigenous to the Caucasus mountain region that divides Europe and Asia. Despite being the second-best source for insecticidal pyrethrum, this species contains far lower concentrations than C. cinerariifolium and is of lesser economic importance.

Pyrethrins, the active ingredients of pyrethrum

The active ingredients of pyrtherum, the pyrethrins, are found in the achenes (seed-cases) of the flower, which are crushed to produce a substance known as an oleoresin, a naturally-occurring mixture of oil and resin. This oleoresin is then further processed to produce an emulsion, suspension, or powder, to be used directly on pest-affected plants.

Pyrethrins are highly toxic, volatile terpenoids. Chemically, they are closely-related esters (usually an end-product of an acid-alcohol reaction) with cyclopropane cores: their neurotoxicity is derived from their instability, which is also largely the reason that they degrade so rapidly upon exposure to air and water.

There are two known pyrethrins, pyrethrins I & II; also contained within the achenes are two other classes of compound, the jasmolins (I & II) and cinerins (I & II). The biological pathway to synthesis of these compounds depends on two different agents: chrysanthemic acid for the I series (known as the chrysanthemates) and pyrethric acid for the II series (termed the pyrethrates), both with which react with an alcohol, cyclopentenolone.

Cinerins & Jasmolins

The cinerins and jasmolins may also have some insecticidal effect, but their efficacy is far lower than the pyrethrins. Cinerins are more effective as insecticides than jasmolins, although both are currently being assessed for their insecticidal properties.

Of the two series of pyrethrins, the compounds of the pyrethrins I group, the chrysanthemates exhibit a stronger insecticidal tendency, and the pyrethrins II, the pyrethrates are more efficient as knock-down agents. A knock-down agent is a substance that does not necessarily kill pests but rapidly disables them, and such agents can be very important as part of a pest-control strategy.

Pyrethrum is thought to be non-toxic to mammals, but is known to affect beneficial insects such as honeybees. Indeed, some processed forms of pyrethrum have been implicated in Colony Collapse Disorder, the global phenomenon currently decimating honeybee populations across the globe.

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Justine

Hey I just wanted to know what is the common that I can use for pyrethrum plant what do I need to say to my nursery to get one of these plants is it a type of daisy or chrysanthemum

08/10/2013

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