QUESTION: Some of the plants I brought in from outdoors seem to have tiny white flying bugs all around them, and are a nuisance. What are they? And what can I do about them?
These are likely whiteflies, and they often ride in on plants that spent summer outdoors. They’re more than a nuisance; they feed on the plant’s juices and can cause the leaves to turn yellow and die. The insects that are flying are the adults, and if you look at the undersides of the leaves you may be able to see the tiny yellow eggs and larvae.
Whiteflies feed on dozens of plant species and they reproduce quickly, so the problem could get out of hand quickly. To get rid of them, remove the badly infested leaves, then rinse the plant thoroughly and spray with an insecticidal soap. Be sure to treat the undersides of the leaves. Repeat the spraying every week or so.
Next fall, examine them closely to be sure there are no pests hitching a ride. Wash the leaves and treat the plants before you move them indoors. There are several other insect pests that you should watch for:
Aphids: they usually gather in clusters on tender young leaves. They also feed on a plant’s juices. Insecticidal soap, or washing with water or rubbing alcohol, is usually effective.
Mealybugs: You may see white, cottony clusters on stems or leaves, or where the leaf joins the stem. They also feed on the plants, so get rid of them by rubbing them off with water or alcohol.
Spider mites: They are barely visible, but you’ll certainly notice the damage – light-colored, speckled areas on top surfaces of leaves. You may see webbing stretching between leaves if there is a heavy infestation. Wash the plant with soapy water, and treat with insecticidal soap a day or two later. It may require diligence and several applications to control these insects.
UT Extension provides a booklet at its Web site that addresses these problems and more: Insects and Related Pests of House Plants (PB1157).