My uncle, who is an avid gardener, noticed mealybugs on some of my houseplants and I’d like some advice on how to get rid of them. He told me that I need to spray them, but I would rather not use any chemicals.
— Rosa Rodriguez, Highwood
Mealybugs can be frustrating to eradicate on houseplants, so prepare yourself for the challenge. Mealybugs can infest many different types of houseplants and quickly spread to adjacent plants. They can also be a problem in the outdoor garden, but I have not seen issues with them outside in this area. They are soft-bodied, wingless insects that appear as white, cottony masses on the leaves and stems of houseplants. Be sure to check under leaves and where stems are joined, since that is often where they are. They feed by drawing sap out of tissue, and the damage can be insignificant at low pest levels. Once populations build up, mealybugs can cause significant damage, including leaf yellowing and curling as the plant weakens. Leaves may begin to drop, and stems die back as the damage increases. As they feed, they produce honeydew that drips on the plant and causes it to be sticky. This encourages the growth of sooty molds in addition to making a mess on your furniture.
Female mealybugs lay their eggs in fluffy white excretions affixed to the plant. The eggs hatch in about ten days and produce 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, so be sure to act quickly to address this insect as soon as you notice it.
As with most plant pests, the best control for mealybugs is preventing them in the first place. Start by carefully inspecting any new plants for mealybugs before bringing them home. Healthy, vigorous houseplants are less susceptible to infestation than weak, underpotted, overwatered and stressed plants. Do not overfertilize, as mealybugs are attracted to soft new growth. Isolate any infested plants to reduce spread. Consider moving infected plants outside to a shady area.
Mealybugs can be a challenge to eradicate, so be persistent as you work to get rid of them. Try removing them manually 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 or two days ahead of time to make sure it doesn’t burn the foliage. Cleaning your plants’ foliage with a leaf shine product regularly will help discourage future infestations. Sturdy plants can be sprayed with a stream of water if mealybugs are present to knock large numbers of them off the plant. A shower head may not have sufficient force to dislodge mealybugs.
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 also be used. My preference is 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, it may be best to dispose of the plant and start over with a new one.
Be diligent and repeat the methods you choose to get rid of mealybugs every five to six days over a course of about three weeks. This should capture all developing 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.
