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Inspect Houseplants for Pests and Disease

by Don Janssen, Extension Educator

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When you acquire new houseplants or bring inside plants that spent the summer outdoors, it's a good idea to inspect them closely for insect problems.

Constant warm temperatures indoors and the obvious absence of natural enemies can turn a few insects into a major pest problem. Some houseplant pests suck on plant juices; others may feed on roots or leaves. Some pests may live in or under plant pots but not feed on or harm the plants.

Sucking pests include aphids, whiteflies, mealybugs, spider mites ant thrips. Aphids are small, soft-bodied insects. They're often green but may be brown, black, pink or yellow. They may or may not have wings. They're usually found on young, succulent growth, such as recently opened leaves, flower buds and flower stems. Cast aphid skins may look like dandruff on the lower leaves or around the pot on the shelf or table.

If the "dandruff" flies away when you shale the plant, it's probably whiteflies. These 1/16-inch insects with snow-white wings are a common greenhouse pest. In flight, they look like tiny bits of white ash swirling in the air. Both the adults and the immature stages feed on the undersides of plant leaves.

Plants that spent the summer outdoors may be hosting sowbugs, pillbugs, spiders, millipedes, and even earwigs that moved into the plants or their containers. Some combination or washing, repotting, removing pot saucers and shaking out the residents, and vacuuming should control most of these pests.

For more conventional houseplant pests, washing the plants under running water in the sink is often enough to dislodge them. Aphids and spider mites often require no other control. Insecticidal soaps are another option. A commonly recommended control for mealybugs is wiping with a cotton ball dipped in rubbing alcohol. Whitefly control usually requires the use of pesticides.

Select a product labeled for use against the pest you want to control on plant indoors. Some houseplants are sensitive to certain pesticides, so be sure to check the label for any cautions to make sure it won't harm your plant. It's often a good idea to test the material on a small portion of the plant before treating the whole thing. Read and follow all label directions whenever using these or other pesticides.

Sometimes a serious infestation is best dealt with by discarding the plant. Unless a plant is particularly valuable, trying to save it may only result in spreading the problem to other plants.

To reduce the potential for pest or disease outbreaks, even healthy-looking newly acquired plants and those coming indoors after spending the summer outside should be inspected closely before you bring them in and then recheck weekly to catch developing problems before they get out of hand. A magnifying glass is a good investment.

(This resource was added September 2003 and appeared in the Lincoln Journal Star Newspaper Sunday edition. For information on reproducing this article or using any photographs or graphics, read the Terms of Use statement)

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