How to Make and Use Pyrethrin Pesticide
Pyrethrin-based insecticides are a class of organic insecticides derived from natural substances found in a single species of the Chyrsanthemum genus (C. cinerariifolium), also known as Dalmation daisy or pyrethrin daisy. Pyrethrin-based products are a very popular class of organic pesticides, since their nerve toxins are effective against many soft-bodied insects but have very low toxicity to humans and animals, including household pets such as cats and dogs. In fact, various shampoos that control head lice in humans and fleas in pets contain pyrethrins.
Many manufacturers market pyrethrin pesticides, but in many cases, these are synthetic versions that have added chemicals. But it is also possible to make your own effective—and genuinely organic—pyrethrin insecticide if you happen to grow Dalmation daisies or have access to them.
What Is Pyrethrin?
The term "pyrethrin" refers to any of the six target plant molecules (esters) which are extracted from C. cinerariifolium to use as a natural organic pesticide. The combined extraction containing multiple pyrethrins is sometimes referred to as "pyrethrum." Similar pesticides made by synthetic chemical processes, often including additives aimed at making the pesticide more long-lasting, are known as "pyrethroid" pesticides. But while pyrethrins are considered organic pesticides, pyrethroids are not.
When to Make and Use Pyrethrin Insecticide
When genuine organic pyrethrin pesticides are commercially available, it may be best to opt for those products, since they have been refined under careful control and will produce predictable results. But in some cases, the pesticides available for sale may be pyrethroids, which are NOT organic. So if a true organic pesticide is your goal, then making your own pyrethrin pesticide may be the best option.
As far as application goes, it's best to regard any pesticide as a last resort, reaching for the spray only when plant damage becomes intolerable. Left alone, populations of garden pests often find their own equilibrium, as predatory insects respond to the appearance of aphids or other damaging insects. But when a particular plant is suffering damage you can't tolerate, then an organic plant-based pesticide such as pyrethrin or neem oil is always a better choice than a synthetic chemical pesticide. Pyrethrin insecticides are effective against a wide variety of insects, including soft-bodied chewing and sucking insects such as aphids, leafhoppers, mealybugs, spider mites, stink bugs, scale, thrips, and whiteflies.
Just because it is organic doesn't mean that a pyrethrin-based pesticide is utterly safe for all living creatures. In fact, pyrethrins are quite toxic to fish and various other forms of aquatic life, so you should never use them around ponds or bog gardens, especially where runoff might reach natural streams.
Pyrethrin insecticides are biodegradable and will break down within a few days in direct sunlight. The insecticide does not persist in the soil or on the crop, which is why it is relatively safe to use within a vegetable garden.
Remember that pyrethrin is highly toxic to most insects. While it is an effective agent against pests, it can also be deadly to the beneficial insects that pollinate your garden and eat pests. It is not wise to broadcast-spray pyrethrum on all your plants. Use the insecticide as a spot treatment only when and where you have a pest outbreak.
Pure pyrethrins have low toxicity to humans and pets, but they are not entirely harmless. Some people have skin sensitivity to these compounds, and oral consumption can lead to digestive distress. You should use proper caution when mixing and using pyrethrin pesticides, as just because they are organic does not mean they are utterly harmless.
Before Getting Started
Making your own pyrethrin-based insecticide can be done using ingredients you probably already have on hand around your home, as well as a few inexpensive extra items. You will also need a garden that has some actively growing Chyrsanthemum cinerariifolium plants. Not just any daisy will do, as only C. cinerariifolium contains the pyrethrins that make for an effective homemade pesticide. In the garden trade, this plant is usually marketed as Dalmation daisy or pyrethrin daisy, and it may be sold according to its previous botanical name, Tanacetum cinerariifolium.
Dalmation daisy is a popular garden plant for cottage gardens or for naturalized wildflower gardens in locations with relatively dry soil. These perennial daisies are hardy in USDA zones 4 to 10, so it's generally possible to find them at most garden centers, especially those that specialize in wildflower selections.
If you don't have your own growing plants, it's also possible to buy cut flowers from a floral shop, as the Dalmatian daisy is a popular cut flower.
What You'll Need
Equipment / Tools
- Airtight plastic container
- Protective mask
- Coffee grinder or mortar and pestle
- Spray bottle
- Dalmation daisy flowers
- Liquid dish soap
- Cooking oil
Gather and Dry the Flower Heads
During their active bloom season (early and mid-summer) harvests some fully opened flowers of your Dalmation daisies. You need not worry about over-harvesting, as vigorous cutting only prompts additional flowering on these plants. But an effective amount of pesticide can be created with as few as 12 flower heads.
Place the harvested flower heads in a paper bag and hang them in a cool, dry, dark place to fully dry. This can take a few weeks.
Store the Flower Heads
Transfer the dried flower heads to a tightly sealed, airtight container and place in a freezer. They will retain their effectiveness for up to six months if frozen. Do not pulverize the flowers until you are ready to mix the pesticide.
Make the Solution
When you are ready to use the pyrethrin pesticide, wear a protective mask and use a mortar and pestle or coffee grinder to pulverize enough flower heads to make 1 cup of fine powder. It is crucial that the powder be quite fine in order to enhance the extraction of the pyrethrins.
Add the finely ground powder to a quart of warm water and let the solution soak for three hours, stirring occasionally.
Strain the Solution
The raw solution will often clog a sprayer, so the next step is to strain it through cheesecloth to separate the pyrethrin-enhanced liquid from the pulverized flower parts.
Next, mix the strained liquid with a teaspoon of liquid soap and a teaspoon of cooking oil to enhance its ability to cling to plants. Mix thoroughly, then pour the solution into a clean spray bottle for application.
Apply the Pesticide
Use the solution as you would any commercial spray insecticide. The strength of homegrown pyrethrin varies, so feel free to experiment with the proportions until you achieve effective insect control.
Make sure to prevent pyrethrin sprays or powders from running off into ponds or water supplies, as pyrethrins are toxic to many forms of aquatic life.
“Less Toxic Insecticides.” | Clemson University
Pyrethrins vs. Pyrethroids: What’s the difference? MGK/Sumitomo Fact Sheet.
Bond, C. and Buhl, K. and Stone, D. Pyrethrins General Fact Sheet Oregon State University Extension Services, 2014
Pyrethrins Fact Sheet, National Pesticide Telecommunication Network