Contact: Diane Relf, Extension Specialist, Environmental Horticulture
Posted April 1997
Although there are only five major groups of insect and mite pests on house plants, they are very difficult to control and highly persistent, once established. The many varieties of house plants are variously susceptible or sensitive to pests and to the pesticides that can be used for control. Furthermore, it is most difficult to eliminate all insects and mites from a plant once it becomes infested. The three steps to controlling pests are:
Step 1 .
Know how to recognize at least the major insect and mite pests that attack foliage plants: aphids, mealybugs, scale insects, whiteflies, and spider mites.
Step 2.
Prevent the introduction of pests into the home or existing plant specimen arrangements:
Step 3.
If a plant is found to be infested with insects or mites:
Control Measures.
There are three general methods for treating infested plants: physical removal or washing; general purpose, ready-to-use sprays; and chemical concentrates for preparing spray mixtures.
Physical removal includes picking off caterpillars, slugs, and other larger pests. Another method is to swab pests with a small brush or cotton swab moistened with rubbing alcohol. This method is feasible when plants are small and infestations very light. It is tedious and must be done once a week over a period of time.
Plants can also be washed in a dilute mixture of water and true soap or insecticidal soap, or gently spray-washed with lukewarm water. Repeated washings over a period of time are necessary to gradually reduce infestations. If the infestation is severe, it may be preferable to discard the plant and replace it rather than attempt chemical control.
Ready-to-use sprays are available from garden stores, but must be labeled for use on house plants. Never use an aerosol intended for other household spraying. Read the label instructions carefully, including all precautions. Some sprays are effective only for certain insects or certain stages of insects, but will not control other stages of insects or mites. Some contain only a miticide or a mixture of a miticide and insecticide. Whiteflies are very difficult to control with some standard sprays, but quite readily controlled with others specifically labeled for whiteflies. Be sure to follow directions. There are many individual products on the market; be sure to read the label to determine which one to use.
Chemical concentrations are available to mix with water for application with a hand sprayer or mister. Insecticides and/or miticides are available separately or in mixtures. Generally insecticides will not control mites, and miticides will not control insects. Only the appropriate pesticide is needed. The wrong one will not be effective.
Insecticides and miticides that are available for ornamental plants in the landscape may be effective for certain pests on houseplants. However, few are labeled for houseplant use, and foliage and houseplants may be injured by the sprays since their sensitivity to pesticides varies widely. The safest approach is to use a given pesticide only for the uses specified on the label. Also look for precautions and warnings of plant injury. Avoid using the chemicals indoors and make sure that you mix only the amount needed so that you do not pour any down the drain.
(Originally published as "Control of Pests on Foliage and House Plants," by J.A. Weidhaas, Jr., Extension Entomologist, VPI&SU, in The Virginia Gardener Newsletter, Volume 9, Number 3.)
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