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Answer to this month's Insect Quiz |
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Answer to this month's Insect Quiz |
You have an infestation of mealybugs. The common mealybugs that infest houseplants often produce the waxy, white covering for protection. The eggs are also protected within the cottony material. Mealybugs tend to occur in clusters on the undersides of leaves and at leaf axils.
The sticky material on the leaves is called honeydew. As the mealybugs feed, they consume more sugars from the sap than they can digest. They excrete the excess as a fluid known as honeydew onto the underlying leaves, tables and other surfaces. Often, the presence of honeydew is the first sign that an insect pest is present. Scales and aphids also secrete honeydew.
Mealybugs extract plant sap as they feed. Light infestations do not seriously injure plants. However, as mealybugs become more abundant, they can eventually cause leaves to wilt, turn yellow, and drop. Mealybugs can even kill plants if they infest them long enough.
Mealybugs are not fussy eaters and will feed on a wide range of houseplants. Although the adults move slowly around the plant as they feed, they can readily crawl to adjacent plants. When the nymphs hatch from the eggs, they will crawl until they find a suitable feeding place.
Keep infested plants isolated from uninfested ones. If you have a light infestation, you can wash the plants with a mild detergent solution (½ teaspoon of diswashing liquid to a quart of lukewarm water). You can also dab the mealybugs with a cotton ball or a swab soaked in alcohol to break down the waxy covering and kill these insects. Don't use alcohol on plants with hairy leaves, such as African violets. Another option is to scrape off the mealybugs gently using a fingernail file or pen knife. If the infestations are limited to just a few branches, just prune them out.
If you have a heavy infestation, an application of an insecticide may be necessary. Insecticidal soap can kill the mealybugs on contact, but repeat applications are probably necessary. Horticultural oil will often smother the mealybugs. You may also use a foliar insecticide with a short residual such as permethrin, cyfluthrin, or bifenthrin, which are also applied to the foliage. Disulfoton has a longer residual but is applied as a granular to the soil. Be sure it is watered into the soil and applied only to actively growing plants. Disulfoton has a disagreeable odor. Do not apply disulfoton to food plants (e.g. herbs). Follow all pesticide label directions carefully.
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