“I started having problems with mealybugs on some of my houseplants and would like some advice on how to get rid of them.”
— Alfredo Patino, Highwood
Mealybugs feed on plants and will infest many different types of houseplants and quickly spread through your collection. They can also be a problem in the outside garden, but I have not seen them cause problems outdoors in the Chicago region.
Mealybugs are soft-bodied, wingless insects that you will see as white cottony masses on the leaves and stems of house plants. Be sure to check under leaves and where stems are joined, as you can often find them there.
They feed by drawing sap out of the tissue, and the damage will be insignificant at low pest levels. Once populations build up, if controls are not implemented, mealybugs can cause significant damage, including leaf yellowing and curling as the plant weakens. Leaves may begin to drop and stems may die back as the damage increases. As they feed, the pests produce honeydew, a liquid which drips on the plant and causes it to be sticky, encouraging the growth of sooty molds.
Female mealybugs lay their eggs in fluffy white excretions affixed to the plant. The eggs hatch in about 10 days, producing crawlers (nymphs) that move to another part of the plant and spend four to eight weeks developing into adults. When temperatures are optimum, a generation of females can take as little as a month to fully cycle through reproduction, so one does need to quickly address the infestation when present.
Like most plant pests, the best control for mealybugs is preventing them. Start by carefully inspecting any new plants for mealybugs before bringing them home. Healthy, vigorous houseplants are less susceptible to infestation than weak, under-potted, overwatered and stressed plants. Do not over-fertilize, as mealybugs are attracted to soft, new growth. Isolate any infested plants if you can to reduce the spread.
Mealybugs can be a challenge to eradicate, so it is important to be persistent as you work to get rid of them. Try manual removal first if the population and number of plants involved is reasonable. Use a drop or two of isopropyl alcohol on a cotton swab and wipe it on the insects to remove them. You may want to test the solution on a small part of the plant one to two days ahead of time to make sure it doesn’t burn the foliage.
Cleaning your plant’s foliage with a leaf shine product on a regular basis will help discourage future infestations, so it may be a helpful strategy for you to employ for a period of time. More sturdy plants can be sprayed with a stream of water to knock large numbers of mealybugs off the plant. It is too cold to do this outside now, and your shower head may not have sufficient force to dislodge the mealybugs. You can also dab the insects with a cotton swab dipped in rubbing alcohol.
There are insecticidal soaps on the market that can be used to control mealybugs. These short-lived natural pesticides work by damaging the outer layer of soft-bodied insects, which causes dehydration and death within a few hours.
There are also more potent synthetic insecticides that can be used. My preference would be to try to avoid this option and only treat when it can be done with the plants outside. The effectiveness of chemical treatments for controlling mealybugs can be reduced by their waxy coating.
If a plant is of low value and you are not getting good results with your treatments, then it may be best to dispose of the plant and start over with a new one.
It is important to be diligent by repeating the method or methods you choose to get rid of the mealybugs every five to six days over a course of about three weeks. This will capture all developing all life stages of eggs, nymphs and adults.
For more plant advice, contact the Plant Information Service at the Chicago Botanic Garden at plantinfo@chicagobotanic.org. Tim Johnson is senior director of horticulture at the Chicago Botanic Garden.
