Rita Pelczar on how to remove common houseplant pests for Better Homes & Gardens.
Give these pesky bugs the boot for good.
Whether you grow a couple of African violets, pamper a fiddle leaf fig tree, or have a houseful of exotic tropical plants, you know that regular care helps keep all your houseplants healthy and happy. But despite all your TLC, from time to time your indoor garden may end up with an infestation of insects or mites. A few bugs won’t do much harm, but if left untreated, they can multiply and turn your favorite potted plant into an ugly mess, or even kill it. But don’t panic. Most common houseplant pests can be controlled with a few simple techniques and a little patience.
“When tackling houseplant insect pests, the first step is to ask yourself how much you value the plant. There are no quick fixes and it will take time and dedication to manage the pests,” says Laura Jesse Iles, director of the Plant and Insect Diagnostic Clinic at Iowa State University. If you decide to treat instead of toss your infested plant, Iles recommends isolating it to keep the problem from spreading to your other plants. Here’s how to get rid of the most common houseplant pests you may find.
Scales are soft-bodied insects that suck plant sap. Tiny crawlers (the immature stage) move a little as they feed. Adults cover themselves in a waxy, protective coating and stay put, so you might not even recognize the small white or brown bumps as bugs. Scales are most likely to be found on the underside of leaves and on stems, although they occasionally appear on the upper leaf surface as well. While they can feed on lots of different houseplants, scales are particularly fond of citrus trees, ivy, and figs.
Scale-infested leaves may turn yellow or drop off, and stems die back. The bugs also produce a sticky substance called honeydew that they leave on your plant. Besides making a mess, the sweet residue can attract ants, plus a black fungus called sooty mold often develops on it (not a good look).
How to Control Scales
Spray your plant with insecticidal soap ($10, The Home Depot) or neem oil ($11, The Home Depot) to smother crawlers. Adults are more difficult to control because of their waxy covering. Use your fingernail to gently scrape them off. If possible, remove heavily infested parts of the plant, such as older leaves. Check your plant regularly and scratch off any scales you see until the infestation is gone.
Mealybugs are similar to scales; they are sapsuckers, have a waxy coating, and make honeydew. “Signs of a scale or mealybug infestation can include the presence of waxy deposits on the plant; of black sooty mold that grows on the honeydew produced by these insects, and (depending on how heavy the infestation is) sometimes yellowing and dying leaves, and distorted or stunted plant growth,” says Natalia von Ellenrieder of the Plant Pest Diagnostic Branch of the California Department of Agriculture. Female mealybugs produce a white, cottony material where they lay eggs that hatch into crawlers. Coleus, hoya, jade, gardenia, and poinsettias are particularly susceptible to mealybugs.
How to Control Mealybugs
Use a cotton swab dipped in rubbing alcohol to remove the mealybugs. For larger, sturdy plants, wash leaves off with a strong spray of water to dislodge the pests. Insecticidal soap and neem oil may be the best option for heavy infestations.
3. Spider Mites
Spider mites are so tiny that you may not even see them. They look like dark specks on leaves, but you’ll probably first notice their white silky webs in leaf axils or along veins. The mites suck sap from leaves and cause them to discolor and drop. Ivies, dracaenas, figs, hibiscus, and scheffleras are a few of their favorite hosts.
How to Control Spider Mites
Mite infestations are tough to control. If your plant is heavily infested, it’s best to get rid of it before the pests spread. “For spider mites and scales, catching the problem early and inspecting plants regularly makes a big difference. You can use some of the easier approaches of removing infested leaves, washing them off with soapy water, and crushing them,” says Kelley Hamby, an entomology professor at the University of Maryland. Increasing humidity around plants may also help limit spider mite build-up.
These tiny, winged insects have a delicate, powdery white appearance. The immature stage doesn’t move much, but the adults flutter about when disturbed. Both stages suck plant sap, but it’s the immature stage that causes the most damage, feeding from the underside of leaves. “Immature whiteflies look a bit like scale insects,” says Iles. Infested leaves turn yellow and die, and the plant is often stunted. Keep a sharp eye out for them, especially on ivies, hibiscus, and poinsettias.
How to Control Whiteflies
An insecticidal soap or neem oil will get rid of whiteflies. “Be sure to apply to the underside of the leaves, where the whitefly immature stages will be,” says Iles. “Treatment will probably need to be done weekly until you no longer see any immature or adult whiteflies.”
Aphids, another sap-sucking pest, also produce sticky honeydew. They can attack lots of different plants and are particularly fond of tender, new growth where they cause distorted growth and wilting. Their life cycle is short (usually 2-3 weeks long) so populations can increase rapidly.
How to Control Aphids
A hard spray of water will dislodge most aphids. Either take your plant outside to hose it down (if it’s not too cold) or use your shower sprayer. Insecticidal soap or neem oil sprays are also effective.
6. Fungus Gnats
Although tiny fungus gnat adults are more of a nuisance than a pest, the immature stage (larvae) feeds on plant roots and can cause growth problems, especially on young plants. “Fungus gnats are often a symptom of overwatering,” says Hamby.
How to Control Fungus Gnats
Allow the surface of soil in pots to dry between watering. Do not let water stand in saucers. Drenching soil with the biological insecticide Bacillus thuringiensis var. israelensis will control the larvae. Yellow sticky traps will help capture adults.