INSECTICIDAL SOAPS -  For over 200 years soaps have been used as insecticides for plants.  Soaps are effective at killing many pests without damaging plants or poisoning the environment.  Like horticultural oils, soaps are applied as diluted sprays (1 to 3 % concentration).  By damaging the cell membranes of the insect pests, insecticidal soaps can quickly destroy harmful infestations on plants.  Mostly soft-bodied, small insects such as aphids, leafhoppers, and spider mites are sensitive to insecticidal soaps.  Some larger insects like Japanese beetles are also susceptible.  To increase effectiveness, some soaps are sold as mixtures with other insecticides. The major advantages to soaps are their selective action and high degree of safety to humans and the environment.  Most insecticidal soaps can be used on a wide-range of vegetable and ornamental plants.  One disadvantage of soaps is that the only work on immediate contact and have no residual effects.  Soap sprays must be applied directly on target pests and a good coverage of spray is essential.  Soaps may be less effective if they are applied when they will dry quickly.  Also, minerals in water can reduce the effectiveness of some soaps.  There are some plants that tend to be sensitive to injury by soap spray so read all labels on specific products.


This web site was created for the Morris Arboretum of the University of Pennsylvania's Plant Clinic.
Created by C. Hetzel and revised by S. Eisenman on 3/7/02.