Pyrethrum is safe for pets and humans, but it kills harmful insects dead — and you can make it yourself
The perennial flower called the pyrethrum daisy, which is actually a kind of chrysanthemum, offers more than ephemeral beauty: the flowers produce a potent pesticide that kills insect pests while leaving most beneficial insects alone. Even better, it’s safe for use around kids and pets.
And guess what? You can make it yourself without much effort at all!
Make no mistake: pyrethrum is poisonous. However, unlike those nasty chemical insecticides that you can buy in most home and garden stores, it doesn’t seem to affect mammals and most beneficial bugs at all — although it can kill ladybugs, because they’re close cousins to the damaging Mexican bean beetle.
Pyrethrum acts as a nerve toxin, so it must be ingested to do its dirty work. Furthermore, it’s biodegradable, so it doesn’t hang around. Within just a few days, sunlight will break it down into harmless substances that will wash away with the next rain. When properly used, it’s as safe as any insecticide can be.
How Do I Make It?
Besides elbow grease, a dash of dish soap, and a little water, all you need is pyrethrum daisies of one of two species: Chrysanthemum cinerariifolium or C. coccineum. You should be able to get the seeds for either fairly easily at a nursery or from a seed catalog.
C. cinerariifolium, also called the Dalmatian chrysanthemum, typically has white petals with a yellow center (though the petals may be other colors as well). This species is a much more potent source of pyrethrum the insecticide than C. coccineum, which is usually white, red, or pink.
The Actual Recipe
Here’s how to create a simple, purely organic, biodegradable and above all safe pyrethrum insecticide:
First, pick fresh, mature pyrethrum flowers, and hang them upside down to dry in some dark, cool place with decent circulation. Once they’re thoroughly dry, grind them up (ideally in a mortar and pestle). Be sure to wear gloves and a breathing mask! Pyrethrum is still a toxin, and may affect you if you ingest it.
Store the resulting powder in well-labeled jars, again in a cool, dark place. Darkness is an absolute requirement, since pyrethrum breaks down in sunlight.
When you’re ready to use the insecticide, mix the powder with enough water to create a sprayable solution, then add a dash of dish soap to help it stick to the plants. Load it into a spray bottle and use it as a foliar spray to kill aphids, thrips, red spider mites, cabbage loopers, bean beetles, whiteflies and more.
If the insecticide doesn’t seem affective, try a more concentrated solution. The concentration of pyrethrum in the flowers can vary due to environmental factors.