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 consistent result. Information from the following website: Homemade Insect Control

Emily L. Revels
Extension Agent
Consumer Horticulture
Cumberland County
(910) 321-6870

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Created by Susan Johnson, System Administrator, July 2005