Issue: December 13, 2008

Houseplant pest management in winter


It is about time for my annual problem to develop. Each year in December my houseplants get bugs. I don't know where they come from, but they suddenly appear and kill some plants. Other plants will be damaged but may survive. Is there anything I can do to save my plants?



There are several insects that are common on houseplants at this time of the year. These include aphids, mealy bugs, and scale insects. Spider mites are not insects (they are mites with 8 legs, not 6 like an insect). Of these, the spider mites may do the most damage because they are often not noticed until they have done considerable damage.

The aphids and spider mites can be managed (not eliminated) by spraying the plant with a strong stream of water to wash them from the plant. To avoid water damage to carpets and furniture, take the plants to the bathtub, shower, or sink to do this. Use a hand held shower head or chemical sprayer containing only water (be sure there is no residue from previous uses) to spray the insects from the plants. A strong stream of water may be needed. Do this regularly, but not so often that you keep the soil soggy. This will at least keep the population of pests low enough to limit their damage.

Mealy bugs will be more difficult to wash off with water and scale insects will be impossible to remove with water. Non-chemical measures involve physically removing them with a cotton-tipped swab. Adding mild chemicals such as oil (horticultural oil or even vegetable oil) or rubbing alcohol will make removing them a little easier.

If stronger measures are required, insecticidal soap sprays (soaps manufactured for this purpose) may be used in the manner described for the water rinse. The soapy water may wash some aphids and mites from the plants, but they also have insecticidal properties and will kill some of the pests that remain on the plant. You must be sure the spray reaches the pests; it will not be effective if it is not sprayed directly onto the pests.

There are other chemical products labeled for control of pests, but many of those are not labeled for use indoors. If you choose to use a product, be sure you use it in the manner described on the label. You can replace houseplants, but your family can't be replaced, so please use any pest control products carefully.

Send your gardening questions to:
Yard and Garden, ATTN: Dr. Curtis Smith
NMSU Cooperative Extension Service
9301 Indian School Road, NE, Suite 112
Albuquerque, NM 87112

Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist with New Mexico State University's Cooperative Extension Service. New Mexico State University is an equal opportunity/affirmative action employer and educator.