How to Get Rid of Fungus Gnats on Houseplants

Fungus gnats have a real knack for annoying houseplant owners. Here's how to banish them for good—without using harmful pesticides.

Proven Ways to Eliminate Fungus Gnats

Dark Winged Fungus Gnat, Sciaridae On A Green Leaf, These Insects Are Often Found Inside HomesTOMASZ KLEJDYSZ/GETTY IMAGES
Dark-winged fungus gnats look like small fruit flies.

“I had a fungus gnat explosion on my overwintering geraniums. Is there an effective, natural way to eliminate fungus gnats other than neem oil? And is neem oil actually a safe solution?” asks Birds & Blooms field editor Sue Gronholz.

Horticultural expert Melinda Myers writes, “Neem is labeled for controlling fungus gnats on houseplants and should not damage the plant when the directions are followed. But understanding how these insects enter our homes and affect our plants will help with control.

Fungus gnats find their way inside by hitching a ride on plants added to our indoor houseplant collection, on plants moved inside after a summer outdoors, or on organically rich, non-pasteurized soil. Fortunately, fungus gnat populations on houseplants seldom reach plant-damaging levels. They are, however, very annoying.

Fungus Gnat Control: Watch Your Watering

Watering can water soil in pot with spatifilum on the white backgroundTatiana Foxy/Getty Images
Allow soil to dry after watering to help control fungus gnats.

Start your fungus gnat control by adjusting your watering practices. Since these gnats thrive in moist soil, avoid overwatering. Allow the top few inches of soil to dry between thorough waterings, and pour off excess water that collects in the saucer to avoid overly wet soil and root rot.

Check out the best indoor plant hacks you need to start doing right now.

Organic Fungus Gnat Treatment

If this alone is not working, treat the soil with an organic Bacillus thuringiensis israelensis (BTI) product, such as Summit Mosquito Bits, labeled for controlling fungus gnat larvae on houseplants. You’ll need to make several weekly applications to manage the existing population, and to apply again if new fungus gnat populations appear.

Just sprinkle the mosquito bits on the soil surface and water. When the wormlike fungus gnat larvae feed upon the Bti, they die. Best of all, the product is safe for pets, people and wildlife.

Having other houseplant problems? Learn what to do if your houseplant has brown tips and brown spots on its leaves, why your plant’s leaves have turned yellow, and how to fix mold on your soil.

Melinda Myers
Gardening expert, TV/radio host, author & columnist Melinda Myers has written more than 20 gardening books. She hosts the nationally syndicated “Melinda’s Garden Moment” TV and radio segments and is the instructor for The Great Courses How to Grow Anything DVD and Instant Video series. Melinda is a dynamic presenter, appearing at many events throughout the country each year. She has received recognition and numerous awards, including the American Horticultural Society’s B.Y. Morrison Communication Award and was inducted into The Association for Garden Communicators Hall of Fame.