2008 Year in Review

Controlling Mealybugs on House Plants

As houseplants are making a comeback, we have to be on the lookout for the insects and related pests that find the plant a perfect meal.

One of the most common, and easy to see, pests are the mealybugs—white, cottony masses about 1/8-inch in diameter on the stems and leaves of your house plants, states David Robson, University of Illinois Extension horticulture educator, Springfield Center.

Mealybugs are insects that feed by sucking the sap out of the plant. Much of the sap is not utilized by the insect, but is excreted as a syrupy solution that makes lower leaves and other surfaces under the plant glossy and sticky. A black mold, called sooty mold, may eventually grow on this syrupy material, especially if the area has a high humidity.

Plants commonly attacked by mealybugs include African violets, sinnigias and other gesneriads, cacti, jade plant and other succulents, avocado, citrus, coleus, palms and schefflera. Infested plants grow slowly, if at all, and frequently have distorted leaves that drop from the plant. Heavy infestations are frequently fatal.

On the other hand, there are some plants, such as philodendron, that can tolerate a mild infestation with little visual damage.

Small plants with light infestations may be successfully treated by dabbing each mealybug with a cotton swab dipped in rubbing alcohol. Be sure to touch only the insect. You may notice the white coating disappear and the pink-colored insect beneath. If you want, you can take a pocket knife to carefully rub the insect off.

Alcohol on leaf tissue will usually cause drying, often resulting in a dead spot on the leaf. That’s why it’s important to wash the plant thoroughly and immediately after using the rubbing alcohol.

For best control, treatments should be repeated weekly for about two months. Don't use too much alcohol and avoid dabbing the growing point, cautions Robson.

Spraying infested plants with an insecticide is also effective. Treat the plants every 10 to 14 days for 2 to 3 months. Large masses of mealybugs at junctures of the leaf and stem and at other locations should be physically removed since young mealybugs within these masses will be protected from the insecticide.

Plants growing in loose soil such as cacti and other succulents should also be checked for mealybugs on the roots and underground stems. Root infestations should be treated every two weeks for two months.

Water the plant to thoroughly moisten the soil. Apply an insecticide, recommended by your local Extension office, as directed on the label to the soil until the solution runs out of the bottom drainage holes. After two months, check the roots for any infestation and repot.

An insecticidal soap will also help control mealybugs and other sap-sucking insects such as scale and aphids. As with any insecticide, read and follow label directions.

For severe infestations, it may be easier, simpler and less time-consuming to simply discard the plant. This also may prevent the insects from attacking other plants.

by  Editor, theCity1.com
January 18, 2008