Plant-Derived Insecticides
Many Organic Insecticides Come From Plants and Fossils
Pyrethrum and pyrethrins. Pyrethrum is a chemical derived from dried chrysanthemum flowers. It has been used for millennia in controlling lice and repelling insects. In small quantities, it repels mosquitoes, and even prevents female mosquitoes from biting. In larger doses, it is a fast and sure killer of many garden and houseplant insects. It also affects many flying and crawling insects. It can be found commercially as Schultz’s plant spray, Bug Buster, Bonide and Time Mist, among others.
D-limoneneThis is an extract made from citrus. It is particularly effective against fire ants, fleas and ticks. It is sold commercially as Citrex, Adams Flea and Tick Shampoo and GreenChem among others.
Diatomaceous earth. Non-toxic and odorless, diatomaceous earth is white and powdery. It is actually made up of finely ground shells of tiny fossilized creatures called diatoms.The final product has tiny, microscopic sharp edges. These edges cut into the insects exoskeletons causing the insects to lose moisture. They generally dehydrate and die within several hours. Insects that eat the powder also die. Diotomaceous earth can be found under many product names.
Corn Gluten.Some studies seem to show that corn gluten has a significant impact on controlling weeds. This is a byproduct of the corn milling process, and has been used as a supplement to animal food. However, recent studies at Iowa State University have indicated that corn gluten has significant impact on weeds when used as a pre-emergent herbicide. There are a number of products on the market, including A-Maize-N, Luscious Lawn and Espoma Organic among other brands.
Boric acid. This natural compound is inorganic, of course. It is often the “secret” ingredient in many insecticides and works extremely well against ants, roaches, silverfish, and termites. The boric acid available in North America comes from mines in the Mojave Desert.
Nicotine. Of course, this is a tobacco extract. But it is also an organic substance. Pure nicotine is toxic to mammals. It is used mainly to kill aphids, leafhoppers, white flies and thrips.
Rotenone. Extract from specific plants in Asia and South America. It is harmless to plants, moderately toxic to mammals, highly toxic to fish and many insects. It has been used to control aphids, caterpillars and some beetle species.
In addition, there is ongoing research in the development of organic pesticides, herbicides and fungicides.
An essential oil found in catmint could act as a repellant to roaches and mosquitoes. Oils of other herbs are also being studied for possible insecticide or insect repellant qualities.
Don't assume that because these are organic that they are not harmless to humans, pets or wildlife. As when using any pesticides, follow directions on the container specifically.
