Soaps are made from fats reacted with a strong lye to form potassium or sodium salts of the fatty acid components. Fatty acid chains containing 6-10 carbon atoms have insecticidal/miticidal activity. These soaps, often called insecticidal soaps, apparently disrupt the respiratory systems and disrupt cell membranes.
Currently available soap products usually contain soaps derived from plant fats and oils. These are often considered "organic" in origin and are considered usable by most organic gardeners.
Mammalian toxicity: Insecticidal soaps have the same general mammalian toxicity traits of any soap or detergent. Contact with mucus membranes, such as eyes or mouth, may cause temporary irritation or a burning sensation. Ingestion may cause vomiting and general gastric upset, but this normally results in no serious consequences. Some insecticidal soap concentrates contain up to 30% ethyl alcohol which can cause intoxication at doses above several ounces; however, vomiting is likely to clear most of the alcohol from the system before it is fully absorbed.
Some insecticidal soap products contain additional insecticidal compounds such as pyrethrins or citrus oils. These alterations change the overall toxicity levels.
Uses: Insecticidal soaps are used as contact pesticides to control a wide variety of insects and mites. Generally, soft bodied insects such as aphids, caterpillars, scale crawlers, leafhopper nymphs, mealybugs, thrips and whiteflies are the best targets. However, some products claim efficacy against Japanese beetle and flea beetle adults.
Soaps are commonly used in more environmentally sensitive areas such as around houses, in interiorscapes and where organic pesticides are requested.
Caution: Common household soaps and detergents have insecticidal properties when applied as 1-2% solutions in water. However, these compounds are not registered for this purpose and plant injury may occur.
Back | Forward | Table of Contents
All educational programs conducted by Ohio State University Extension are available to clientele on a nondiscriminatory basis without regard to race, color, creed, religion, sexual orientation, national origin, gender, age, disability or Vietnam-era veteran status.
Keith L. Smith, Associate Vice President for Ag. Adm. and Director, OSU Extension.
TDD No. 800-589-8292 (Ohio only) or 614-292-1868