Plant and Garden

What is Pyrethrin? Plants Saving Plants By Killing Bugs!

Pyrethrin insecticide kills insects on contact because it’s derived from the pyrethrum daisy (Chrysanthemum cinerariifolium), also nicknamed the Dalmatian chrysanthemum.

orange chrysanthemum flowers in closeup photo
Photo by Deva Darshan

This chemical has been produced synthetically by industrial methods. However, this perennial daisy contains deadly nerve toxins naturally.

Therefore, it’s often considered an organic insecticide when it is not combined with piperonyl butoxide or other synthetic adjuvants.

The active chemicals, the “pyrethrin’s“, are toxic to insect nervous systems.

Be careful not to confuse pyrethrum with pyrethrin. Pyrethrin refers to a more refined extract of pyrethrum. Pyrethrin is in body lice medicines such as A-200 Pyrinate, Barc, Lice-Enz, Licetrol, Pronto, R and C, RID, Tisit, Tisit Blue, and Triple X.

Pyrethrins are gradually replacing organophosphates and organochlorides as the pesticides of choice as the latter compounds have been shown to have significant and persistent toxic effects on humans. Because they are biodegradable pyrethrins are widely preferred to pyrethroids, which are synthetic analogs of pyrethrin that accumulate in the environment.

The pyrethrin’s occur in the seed cases of the perennial plant pyrethrum (Chrysanthemum cinerariaefolium), which has long been grown commercially to supply the insecticide.

photography of the temple
Photo by David Besh

Pyrethrin’s have been used as an insecticide for thousands of years. It is believed that the Chinese crushed chrysanthemum plants and used the powder as an insecticide as early as 1000 BC. It was widely known that the Chou Dynasty in China widely used pyrethrin for its insecticide properties

For centuries, crushed Chrysanthemum flowers have been used in Iran to produce Persian Powder, an insecticide for household use. Pyrethrins were identified as the potent chemical in the Chrysanthemum plants responsible for the insecticidal properties in the crushed flowers around 1800 in Asia. In the Napoleonic Wars, French soldiers used the flowers to keep away fleas and body lice.

Pyrethrin was commonly known as “Persian powder”, “Persian pellitory”, and “zacherlin”.


Pyrethrins delay the closure of voltage-gated sodium channels in the nerve cells of insects, resulting in repeated and extended nerve firings. This hyperexcitation causes the death of the insect due to loss of motor coordination and paralysis.

Resistance to pyrethrin has been bypassed by pairing the insecticide with synthetic synergists such as piperonyl butoxide. Together, these two compounds prevent detoxification in the insect, ensuring insect death.

Synergists make pyrethrin more effective, allowing lower doses to be effective. Pyrethrins are effective insecticides because they selectively target insects rather than mammals due to higher insect nerve sensitivity, smaller insect body size, lower mammalian skin absorption, and more efficient mammalian hepatic metabolism.

Although pyrethrin is a potent insecticide, it also functions as an insect repellent at lower concentrations. Observations in food establishments demonstrate that flies are not immediately killed, but are found more often on windowsills or near doorways. This suggests, due to the low dosage applied, that insects are driven to leave the area before dying.

crop field under rainbow and cloudy skies at dayime
Photo by James Wheeler

Because of their insecticide and insect repellent effect, pyrethrins have been very successful in reducing insect pest populations that affect humans, crops, livestock, and pets.

Bugs and pests such as ants, spiders, worms, beetles, and lice, as well as potentially disease-carrying mosquitoes, fleas, and ticks.

As pyrethrin’s and pyrethroids are increasingly being used as insecticides, the number of illnesses and injuries associated with exposure to these chemicals is also increasing.

However, a few cases leading to serious health effects or mortality in humans have occurred, which is why pyrethroids are labeled “low-toxicity” chemicals and are ubiquitous in home-care products.

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Pyrethrin’s are widely regarded as better for the environment and can be harmless if used only in the field with localized sprays, as UV exposure breaks them down into harmless compounds.

Additionally, they have a little lasting effect on plants, degrading naturally, or being degraded by the cooking process.

Specific pest species that have been successfully controlled by pyrethrum include potato, beet, grape, and six-spotted leafhopper, cabbage looper, celery leaf tier, Say’s stink bug, twelve-spotted cucumber beetle, Lygus bugs on peaches, grape and flower thrips, and cranberry fruit worm.


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Photo by Pixabay

Commercial pyrethrin production mainly takes place in mountainous equatorial zones. The commercial cultivation of the Dalmatian chrysanthemum takes place at an altitude of 3000 to 6000 meters above sea level.

This is done because pyrethrin concentration has been shown to increase as elevation increases to this level. Growing these plants does not require much water because semiarid conditions and a cool winter deliver optimal pyrethrin production. Another variety of Chrysanthemum used for the production of pyrethrin’s is the pyrethrum chrysanthemum. These flowers prefer to be grown in dry soils at a lower altitude than the Dalmatian chrysanthemum to optimize pyrethrin production.

Most of the world’s supply of pyrethrin and C. cinerariaefolium comes from Kenya, which produces the most potent flowers. Other countries include Croatia (in Dalmatia) and Japan. The flower was first introduced into Kenya and the highlands of Eastern Africa during the late 1920s. Since the 2000s, Kenya has produced about 70% of the world’s supply of pyrethrum.

tender chrysanthemum morifolium flowers growing in greenhouse
Photo by Yuri Yuhara

A substantial amount of flowers is cultivated by small-scale farmers who depend on it as a source of income. It is a major source of export income for Kenya and a source of over 3,500 additional jobs. About 23,000 tons were harvested in 1975.

The active ingredients are extracted with organic solvents to give a concentrate containing the six types of pyrethrins: pyrethrin I, pyrethrin II, cinerin I, cinerin II, jasmolin I, and jasmolin II.

Processing the flowers to cultivate the pyrethrin is often a lengthy process and one that varies from area to area. For instance, in Japan, the flowers are hung upside down to dry which increases pyrethrin concentration slightly.

To process pyrethrin, the flowers must be crushed. The degree to which the flower is crushed has an effect on both the longevity of the pyrethrin usage and the quality. The finer powder produced is better suited for use as an insecticide than the more coarsely crushed flowers. However, the more coarsely crushed flowers have a longer shelf life and deteriorate less.


Pyrethrins are applied broadly as nonspecific insecticides. Bees have been shown to be particularly sensitive to pyrethrin, with fatal doses as small as 0.02 micrograms.

bee on a plant
Photo by Lisa Fotios

Due to this sensitivity and pollinator decline, pyrethrin’s are recommended to be applied at night to avoid typical pollinating hours, and in liquid rather than dust form.

Pyrethrin is an insecticide that kills a wide range of insect pests including ants, mosquitoes, moths, flies, fleas, and cactus bugs.

Pyrethrin kills off insects almost instantly upon contact. Only apply Pyrethrin in smaller, spot sprays. You do not need to use a lot.

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Photo by Pixabay

However, be careful not to overuse this insecticide product – take care to avoid using beneficial insects such as ladybugs and honey bees. Therefore, only use pyrethrin in situations where it will not affect these types of insects.

Additionally, pyrethrin breaks down rapidly, so it does not persist in the environment. This means pyrethrin-based sprays are often considered compliant for organic production, unlike many synthetic pesticides.

Mix the pyrethrin pesticide with water. In most cases, pyrethrin insecticides will need to be diluted before use. A typical formula is 1 to 4 tsp. for every gallon of water. You will then place the mixture inside a spray gun or watering can for application.

Apply the pyrethrin to the plants or vegetables that you wish to treat. Pyrethrin is safe to use on apple trees, plums, oak, elm, petunia, aster, marigold, peas, squash, cabbage, cedar, cucumbers, potato, and willow. Check the manufacturer’s recommendations on the pesticide product to determine any plants, flowers, and trees that you can use pyrethrin on.

Put the pyrethrin directly on the plants and trees that you wish to protect from insects. Don’t place the pyrethrin on vegetable plants within three days of harvesting. You can repeat the application every week as needed.


Remember to read all warnings found on the pyrethrin insecticide product before use. It may pose a risk to household pets if the animal is exposed to a large amount.

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