Soaps Commercial insecticidal soap (a special formulation of fatty acids) has been proven effective against aphids, leafhoppers, mealybugs, mites, pear psylla, thrips, and whiteflies. Soaps and oils seem to disrupt cell membranes and must have direct contact with soft-bodied insects to be effective. Soaps are not very effective against insects with heavy cuticles or those that are highly mobile. Most adult beneficial insects are not harmed by soap sprays, but the immature stages can be since they often have soft bodies and have limited mobility. Soaps can also aid in the passage of insecticides through the waxy insect cuticle. Some plants can be damaged by soap sprays because they break down the waxy protective outer layer on the plant surface. Homemade soap sprays also work to some extent: mix 3 tablespoons of soap flakes (not detergent) per gallon of water and spray on plants until dripping. Dishwashing detergents and laundry products may damage plants. Some home "recipes" call for cleaning agents, fuel oils, polishes, solvents, and other materials that may be very toxic to plants and animals (including humans). Commercial products deliver a more consistant result. Homemade repellents - Repellent sprays, such as garlic sprays and bug sprays (made from a puree of bugs), have been found useful by some gardeners, but their effectiveness is short lived and poorly documented. Some researchers believe that bug sprays may work if a disease is present in the insect, which is spread through the spray to other insects.

Consumer Horticulture | Quick Reference © Erv Evans, Consumer Horticulturist Shoprights NC State University