How to Get Rid of Fungus Gnats in Your Houseplants (Because They’re Annoying and Gross)

Got houseplants? Chances are you’ve got fungus gnats too. These teeny bugs are only about 1/16th of an inch long and often are seen flitting around near houseplants or in rooms where you have lots of greenery. Are they harming your plants? And how can you get rid of fungus gnats, anyway?

First, know that you’re not alone in your struggle to deal with these soil-dwelling pests. But fungus gnats are not as big of a problem as they might seem: “They’re not harmful to people or pets, but they are annoying,” says entomologist Michael Skvarla, PhD, assistant research professor of arthropod identification, Penn State University. “As their name indicates, they feed on fungus in houseplant pots, especially plants that stay moist.”

Here’s what else you should know about your uninvited houseguests:

Fungus gnats are the adult forms of the larvae, which are what feed on the naturally occurring fungus in houseplant pots. “The adults don’t feed at all. They have no functional mouth parts and survive from the energy reserve they built up as larvae,” says Skvarla. The adults have one job: to fly around and find a mate.

Once their task is accomplished, the females lay eggs in your houseplant’s soil. The masses of 100 to 150 eggs are so small that you won’t see them. They will become larvae—which also are impossible to see—and then adults. (Side note: Kinda gross, we know. But it’s just nature, so don’t freak out too much.)

At night, the adult fungus gnats hang out on walls or other surfaces and wait for daytime. However, they do fly toward light sources, such as a lamp in your living room or bedroom, in search of daylight, says Skvarla. That’s often when you’ll find them flitting around your face.

Good question! Fungus gnats are everywhere outdoors; they’re so tiny and numerous that you won’t even see them sneak in when you open a door or window. Once inside, they look for a place to lay eggs, starting a new generation in your pots. The more houseplants you have, the more safe harbors they have. Sometimes, you also may bring home a plant that’s already infected, and it’s easy for them to spread to other houseplants.

Once they’re established, they continue to mate, lay eggs and hatch indoors, which is why you keep seeing them once you have them. Good news: The life cycle is pretty quick, and adults only live about 10 days. Bad news: “They can double their population in 17 days, so it doesn’t take long for the numbers to ramp up,” says Skvarla.

Not really. The only exception is if you are seed-starting something like tomatoes or peppers for your vegetable garden. If you have lots of seedlings and fungus gnats indoors in high density, the larvae could feed on the sensitive, young roots, which could kill the baby plants. But that’s a long shot and is more likely to happen in a greenhouse setting, not in just a few pots that will be growing in your home short-term before you plant them outdoors, says Skvarla.