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What Is Pyrethrin?

Pyrethrin can be used as an insecticide.
Pyrethrin is considered to be relatively nontoxic to mammals.
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  • Written By: Karyn Maier
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  • Last Modified Date: 09 December 2014
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Pyrethrin refers to a class of organic compounds collectively known as pyrethrins that are derived from the parent chemical, pyrethrum. Although there are six major types, the most common are a pair of esters distinguished from each other as pyrethrin I and II. Both possess a base cyclopropane molecular structure. However, type I has one less oxygenated carbon molecule than type II.

Generally speaking, pyrethrin is the active constituent of the flowers of the pyrethrum plant, better known as chrysanthemum. A member of the daisy family, several related species are grown as perennial ornamentals. However, the compound is obtained from either the Dalmatian chrysanthemum (Chrysanthemum cinerariaefolium) or the Persian chrysanthemum (C. coccineum), also known as Painted Daisy. These two species are grown commercially to produce pyrethrin to be used as an insecticide. While other chrysanthemums also possess insecticidal properties, they are not as effective.

Pyrethrin is produced from the flowers of the plant by one of two methods. The flowers are dried and ground into pyrethrum powder, or they are subjected to solvents to extract the volatile oils to produce a resin. The compound is sold under several different trade names.

The species from which pyrethrin is obtained are considered excellent insect deterrents even in their natural state. This is because they exhibit protective effects on neighboring plants and protect them from infestation. In fact, these plants are often featured in companion planting, a method of natural pest control used by organic gardeners.

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Pyrethrin is classified as a neurotoxin. It quickly permeates the shell or skin of the insect and causes immediate paralysis. However, in the event that a large area or a large number of insects are being treated, it may only be effective as a "knockdown" measure. In fact, the insect’s protective enzymes will degrade the insecticide and permit recovery. For this reason, pyrethrin may be administered in combination with organophosphates or carbamates to deter enzyme activity and ensure a lethal dose.

In general, pyrethrins are considered relatively nontoxic to mammals, including humans. However, type I is deemed a "Restricted Use Pesticide" by the United States Environmental Protection Agency, and its availability and use is limited to certified applicators. This may be due to the fact that pyrethrins are highly toxic to fish, and moderately toxic to birds and bees. The compounds do not persist in the environment since they readily biodegrade when exposed to oxygen, moisture and sunlight.

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Oceana
Post 5

Pyrethrin is an active ingredient in many flea and tick control products. Pyrethrins are a good choice for dog owners like me who wish to use all-natural products. These products are safe for dogs in the specified dosage.

However, if an overdose of pyrethrin is given, the toxins can interfere with the nervous system of the pet. Small dogs can be affected more easily than large dogs. Pyrethrins should not be used on cats.

The package of my flea and tick control medication lists signs of an overdose in dogs as drooling, tremors, decreased appetite, diarrhea, vomiting, disorientation, hyperactivity, difficulty breathing, and seizures, with death being possible. A pyrethrin overdose in cats may present itself as ear flicking, skin twitching, or paw shaking.

StarJo
Post 4

The pyrethrin of chrysanthemums helped me maintain my miniature pumpkin garden last summer. I grew the tiny pumpkins for future decoration during October and November. Beetles the previous year had covered my pumpkin plants, eating at the leaves, stems, and baby pumpkins. I had to pick them off by hand every single day.

After I planted chrysanthemums, I noticed considerably fewer pests. Though I still had to pick a few off now and then, the pyrethrin made the task easier.

shell4life
Post 3

@Perdido - If you grow tomatoes, chrysanthemums can really help you out with insect problems. I grew them next to my tomatoes last year, and my pest problem really decreased.

Chrysanthemums repel tomato hornworms, those large, squishy green worms that eat stems, whole leaves, and small unripe tomatoes. I have always had lots of these insects on my plants, but last year, I hardly saw any.

Chrysanthemums also repel Japanese beetles and leafhoppers. These pests munch on the leaves of plants, leaving them with a filigree appearance. Since both of these types of insects munch on a large variety of plants, you might do well to scatter your chrysanthemum plantings throughout your garden.

Perdido
Post 2

I have some chrysanthemums that need dividing. I also have a vegetable garden. Can anyone tell me what vegetables I should transplant my new chrysanthemums next to so that they will repel insects?

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