What Are Fungus Gnats?

Outdoors, fungus gnats feed on fungi and organic matter in the soil as it breaks down.

Indoors, they’re an unwelcome pest that lays eggs in your houseplants' soil.

Yellow sticky trap covered in fungus gnats in the dirt of potted snake plants.

Devon Nodolski / Getty Images

Once fungus gnats are introduced, it’s easy for them to spread.

You’ll see them buzzing around, which can be a nuisance.

Fungus gnat larvae can chow down on the roots of your plants.

A fungus gnat pest on the leaf of a houseplant

The Spruce / Adrienne Legault

An infestation can cause wilting, slow growth, or even plant death.

Want more gardening tips?

Where Do Fungus Gnats Come From?

Gnats on sticky trap

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Here are some of the common treatments that didn’t solve my fungus gnat problem.

The fungus gnats persisted.

They enter the bodies of fungus gnat larvae in the soil and secrete a bacteria that kills them.

fungus gnats on sticky trap

Marc Leupold / Getty Images

I applied these to all of my plants according to package directions, but the infestation continued.

Use them to gauge fungus gnat levels and see if other treatments are making progress.

It’s non-toxic to people, birds, mammals, fish, and beneficial insects.

I use sticky traps to gauge whether they’re cleared for entry.

Bacillus thuringiensis israelensis(Bti) Fact Sheet.Maryland Department of Agriculture.

Bti for Mosquito Control.United States Environmental Protection Agency.