Your favorite houseplant suddenly isn’t looking too great. Maybe it’s dropping leaves or you found some weird sticky substance all over it. Or perhaps you discovered something that looks suspiciously like cotton but seems to be moving! Ick! Your plant has pests, and you’ve got to act fast to save it. You also should check nearby plants for signs of infestation.
Houseplant pests typically hitchhike a ride into your home. “Insects can be present when you purchase a plant, though you may not see them,” says Shimat Joseph, Ph.D., associate professor, department of entomology at the University of Georgia. “The conditions inside your house create the ideal environment for them to multiply, so their populations explode. Or they come indoors on a plant that spent the summer on the patio.”
To stay ahead of these uninvited guests, inspect houseplants regularly, especially in crevices and on the undersides of leaves, says Joseph. If possible, isolate a new plant for a few weeks before introducing it to the rest of your collection. Ditto for plants you’re bringing indoors for winter. Or give all plants a preventive spray with insecticidal soap or neem oil before bringing them in for the season. Be sure to read the product label because not all products treat all insects nor are they safe on all plants. Also, spray plants outside so you don’t drip all over interior surfaces, and let them dry before bringing them indoors.
However, the sad truth is that sometimes you’re going to need to practice some tough love. If you’ve battled an infestation for a few weeks to no avail or if your plant looks stunted and sad, it’s likely not going to recover. It’s time to toss it, says Joseph. Invest in a new plant, and chalk it up to experience!
Here are the most common insects that infect houseplants and what to do about them:
Spider Mites
What they look like:
Cream-colored specks about the size of a period on the printed page, especially on the undersides of leaves; silk webbing also may be present. You’ll often see dropped foliage or light-colored spots on leaves before you ever notice spider mites.
What to do:
Take the plant outside, and spray all surfaces with neem oil, insecticidal soap or a homemade mixture of one gallon of water and a few drops of dish soap, such as Dawn. Repeat for a couple of weeks and watch your plant closely; use a magnifying glass, and make another application if you see activity. Persistence often succeeds with spider mites, says Joseph.
Whiteflies
What they look like:
Tiny white-winged insects about the size of a dash on the printed page. They excrete a sticky substance, honeydew, on plant surfaces.
What to do:
Take the plant outdoors and spray with an insecticidal soap, coating all surfaces. Repeat every few days. A systemic product, which is applied to the soil surface, may be needed for serious infestations of whiteflies, although you’re probably better off tossing heavily infested plants, says Joseph.
Scale
What they look like:
A waxy brown or greyish substance that resembles a fish scale; you also may see sticky honeydew.
What to do:
Some types of scale are soft, and some have a hard shell, or armor, over them for protection. You’ll have the best luck if you catch these insects in their crawling juvenile stages when their waxy coat is not present to protect them. Use a neem oil to spray the babies, but a systemic product may be necessary for adults. These are challenging to treat so you may need to discard the plant, says Joseph.
Mealy Bugs
What they look like:
Oval, fuzzy white insects about 1/8 to 1/4-inch long; they’re slow-moving. Adults have a waxy cottony-looking coating, while immature bugs are smaller but similar. They’re often on the lower surfaces of leaves or where leaves attach to the stems.
What to do:
Small infestations may be controlled by applying 70% isopropyl alcohol with a cotton swab directly to the bugs. Or spray with an insecticidal soap. However, for large infestations, you should dispose of the plant, says Joseph.
Fungus Gnats
What they look like:
Tiny gnats about 1/8-inch long that hang out on or near houseplants. They’re also attracted to light and moisture.
What to do:
Finally, some good news! Fungus gnats feed on the organic matter in the soil, but it’s unlikely they’ll harm your plant. They’re just super annoying. Cut back on watering, if possible, because dry conditions help kill the larvae. Or use yellow sticky traps to catch the adults. Another choice is to apply a product containing Bacillus thuringiensis var. Israelensis to the soil of houseplants to kill the larvae.
