In common conversation, organic gardening and agriculture generally means growing plants, flowers, and vegetables without insecticides. However, the National Organic Program, managed by the United States Department of Agriculture (USDA), has specific definitions that allow for some safer insecticide use. The certification program of insecticides certified as organic is voluntary and administered by the private agency Organic Materials Review Institute (OMRI).
Insecticides Deemed Organic
A number of commercially produced insecticides meet OMRI certification. Certain bacteria that are generally found in soil can have insecticidal properties and can kill insects on plants. In some cases, naturally occurring viruses can kill insects and can be a part of organic insecticides. Some insecticides mix things such as rosemary, wintergreen, and mineral oil to interfere with insect life. Diatomaceous earth is another organically certified insecticide that works by drying out insect bodies.
Insecticidal soaps are different from the soap used to wash dishes, hair or hands. Insecticidal soap is made with higher levels of certain fatty acids that interfere with insects and often kill them. Insecticidal soaps also do not contain things like dyes and fragrances that might be harmful to your plants. Some insects killed by insecticidal soaps include aphids, spider mites, psyllids, earwigs and thrips.
Companion planting is a way of discouraging insect infestations, rather than killing the insects. However, in some cases, the roots of some plants can secrete substances that kill harmful microbes and soil in the earth. Common flowers used in companion planting to control insects include garlic, catnip, oregano, marigold and petunias.
Another way to deal with an insect infestation is to release the insects' natural predators. For example, people who find infestations of aphids often release ladybugs. Ladybugs are a natural aphid predator. By releasing large numbers of ladybugs, the ladybugs will feed on the aphids before continuing on to other areas.
Barriers can sometimes prevent certain types of bugs. For example, people having trouble with slugs sometimes surround the problem area with copper strips or copper tape. In some cases, netting or other physical barrier can prevent insects like grasshoppers or locusts from reaching certain plants.