Using organic materials for gardening or yard care is appealing to many home owners or gardeners because they are generally considered safe to use. This isn't always the case. Some organic pesticides can harm both your body and the environment if not used properly. The U.S. Environmental Protection Agency recommends that you read and follow the instructions and warnings on the label to ensure safe and proper usage.
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Bacillus thuringiensis, more commonly referred to as Bt, is a biological pesticide, which means it is a living organism that is in some way lethal to garden or yard pests. Bt is ingested by insects and produces a protein that is toxic to some insects. Different strains of Bt are used to control different types of insects, including moths, beetles, flies and mosquitoes. Researchers at the Aroian Lab on the campus of the University of California, San Diego report that Bt was first used as a pesticide in the 1920s.
Another biological pesticide, Beauveria bassiana, is a fungus that infects aphids, caterpillars, grasshoppers, ants and other insects and multiplies until it kills its host. The organic farming book, "Resource Guide for Organic Insect and Disease Management," reports that this fungus occurs naturally in some soils but is cultivated specifically as an organic pesticide.
Kaolin clay is a type of clay that, according to the U.S.EPA, was approved as an organic pesticide in 1998. It is used on various types of produce to protect against mites, insects, fungi, and harmful bacteria. It is sprayed on plants or trees in a powdered form to act as a physical barrier between pests and the plants.
Neem oil is a brown oil with an unpleasant taste and smell that acts as a repellent for insects and is non-toxic to humans and beneficial insects such as honey bees. The U.S. EPA reports that neem oil is pressed from the seeds of the neem tree, which is native to India.
Although pyrethrum is a natural botanical pesticide that comes from dried flowers, not all forms of this pesticide are approved for organic use because of the levels of toxicity it can contain, states the "Resource Guide for Organic Insect and Disease Management." Mixtures of pyrethrum that have been approved for use in organic farming will be labeled as such.
There are several different types of plant oils that are used as organic pesticides. The U.S. EPA lists orange oil, canola oil, mustard oil, castor oil and soybean oil among them. They are used to either kill or repel insects and are also used to repel larger pests, such as cats, dogs or deer. Of all the plant oils approved for use as organic pesticides, only wintergreen oil is noted for having a toxic effect on humans in high doses.