Aphids & Spider Mites on House Plants

- Protect plants with insecticidal soap -

Summary: A small number of insects and mites are the main pests of house plants. Aphids, spider mites and scale insects are the most common and all three can be managed with very low toxicity insecticidal soap.

Jack DeAngelis, PhD
OSU Ext. Entomologist (ret.)

Common house plant pests

Aphids, spider mites and scale insects are the most common and damaging insect pests on house plants. All three damage plants when they feed on plant sap. Aphids may also infect plants with plant pathogens or inject plant toxins that cause growth deformities such as twisting of new growth and stunting (see What are Aphids?, What are Spider Mites?, and What are Scale Insects? for more information).

The most important step in control of these pests is early detection. Check plants often and treat as soon as pests are found. Scout for aphids along stems, especially at the tips, flower buds, and leaves. Cast "skins" and sticky honeydew are early indicators of an aphid infestation. Look for spider mites also on the undersides of leaves. Use your hand lens to carefully search a few leaves on each plant.

As you gain experience you'll learn which of your house plants are more susceptible so you can concentrate on these in the future. Look for scale insects along the stems and leaves. Scales are generally larger than spider mites (except the crawler stage) and should be easier to find.

spider mite drawing

Drawing of a spider mite, highly magnified.

Control of aphids & spider mites

Infestations on house plants often are more severe than infestations on plants grown outdoors. This happens because pest populations on plants that are indoors are protected from predators and parasites and so can grow unchecked. For example, aphids are generally kept under control by lady beetles and other predators. Once you bring plants and pests indoors you separate them from their "natural enemies".

One way to counter this is to move plants outdoors when weather permits. This will allow natural enemy populations to find these plants and reduce their numbers. Be sure to check plants for hitch-hiking pests when they are brought back indoors..

For all three pests treat infested plants with insecticidal soap as described on the spider mite page (see What are Spider Mites?). If the infestations get away from you, and considerable plant damage is evident, it is sometimes best to simply discard the individual plant and start over. New botanical insectcides can be used indoors for a variety of pests. See label instructions for these applications and as with any insecticide, please read and carefully follow these instructions.

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