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Pyrethrum, Pyrethrins, Pyrethroids - What’s the Difference?

Posted in Pest Advice on July 10, 2018

Common Household Insecticides 

If you look at the ingredients of insecticides you might be forgiven for being confused by what the difference is between pyrethrum, pyrethins, pyrethroids and permethrin. Some say they contain pyrethrum, some say they contain pyrethrins, some say they contain permethrin and others with different names that are referred to as pyrethroids. What is the difference?

This is an explanation of what these terms mean.

Pyrethrum (Py)

Pyrethrum is a natural insecticide extracted from the daisy-like Chrysanthemum (Tanacetum cinerariaefolium), sometimes known as the pyrethrum daisy.

Pyrethrum flowers have been used to control insects for 2,000 years. For ~150 years pyrethrum powder has been produced commercially. Today, and for the last 60 years, pyrethrum extract has been refined from plants grown in the highlands of East Africa and other parts of the world.

Pyrethrum is non-persistent and is broken down rapidly in the environment by UV light and changes in pH. This makes it safe to use on fruit and vegetables and for quick knock-down or in repeated use. E.g. Kiwicare Organic Insect Control.


Pyrethrum is a mixture of 6 related molecules known as pyrethrins.

Pyrethrins are effective on a broad range of insects and yet present a very low risk to humans and pets when used around the home. 

Some products describe the pyrethrum extract as the active ingredient pyrethrins.


Pyrethroids are synthetic chemicals that mimic the activity of pyrethrins, but they are more persistent, resisting the action of UV and pH, so they remain effective for longer and are used for long term, residual, insect control.

Both pyrethrins and pyrethroids induce a toxic effect within the insect by acting on sodium channels in insect nerve cells. Pyrethrins and pyrethroids repel and kill insects that are present. E.g. Kiwicare NO Bugs Super.


Just to confuse the pyrethrum-pyrethrin-pyrethroid name similarity confusion further, permethrin is one of the synthetic pyrethroid insecticides.

Examples of pyrethroids: Permethrin, Tetramethrin, d-Phenothrin, Transfluthrin, Lambda-Cyhalothrin, Deltamethrin, Tau-fluvalinate and Alpha-cypermethrin. Each has different properties that make them useful for home and garden insect pest control. E.g. Kiwicare NO Spiders Total Protection.

As you can see, many, but not all names of pyrethroid insecticides end in 'thrin'.

David Brittain

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