Tiny flies, soggy soil
Fungus gnats breed in damp potting soil, so the fix usually starts with the watering can.
Let soil dry.
Letting the top inch or two dry out between waterings keeps the larvae from surviving.
Trap the adults.
Yellow sticky traps near the pots catch adults and show you which plants are the source.
Swap bad soil.
Badly infested plants may need fresh potting soil in a clean pot.
Fungus gnats are tiny dark flies that breed in damp houseplant soil. Overwatering is the usual cause. Let the soil dry out, catch the adults with sticky traps and the problem usually fades within a few weeks.
Our home pest control plans cover a long list of household pests. Coverage for fungus gnats depends on the situation, so call 913-735-5451 and we’ll tell you what fits your home. Either way, most fungus gnat problems start and end with the plants.
What are fungus gnats?
Fungus gnats are small, dark, long-legged flies about the size of a fruit fly. You’ll see them hovering around houseplants or walking on the soil. They’re weak fliers and don’t bite.
Their larvae live in the top couple of inches of moist soil and feed on fungi and decaying plant matter. Heavy numbers can damage the roots of seedlings and young plants.
Why do I have fungus gnats in my houseplants?
Wet soil is the reason. Fungus gnats lay their eggs in potting soil that stays moist, especially mixes rich in peat or compost.
- Watering too often, especially in winter when plants dry slowly
- Saucers that hold standing water
- Pots without drainage holes
- A new plant that came home with gnats in its soil
- Open bags of potting mix stored in a damp garage or basement
How do you get rid of fungus gnats?
Dry out the soil and trap the adults. Most problems clear up once the larvae run out of damp soil to live in.
- Let the top 1 to 2 inches of soil dry before watering again.
- Empty saucers after watering.
- Water from the bottom so the top layer stays dry.
- Set yellow sticky traps at soil level.
- Repot badly infested plants in fresh soil and a clean pot.
- Toss old, open bags of potting mix.
Are they fungus gnats or drain flies?
If the flies hang around sinks and drains instead of plants, you may have drain flies. Fruit flies, on the other hand, hover around ripe produce and trash.
Drain flies are covered on our plans, but success depends on removing the organic buildup in drains, disposals and damp spots. Our post on bugs in the bathroom covers drain flies and other bathroom pests. If small bugs seem to appear out of nowhere, see our guide to sudden bugs in the house.
When should you call a pro?
Call us when flies keep coming after you’ve fixed the watering, or when you can’t tell where they’re coming from. We inspect the home and entry points to find the source and email you a report.
Tiny flies near the sink instead? Read about fruit flies and drain flies. Little jumping bugs in the soil? See springtails.
Flies still buzzing after the soil dries out? Call 913-735-5451, answered 24/7, or schedule online. Most services can be scheduled same day.
Frequently Asked Questions
No, fungus gnats don’t bite people or pets. Large numbers of larvae can damage the roots of seedlings and young plants, but grown houseplants usually handle them fine.
Most fungus gnat problems fade within a few weeks once the soil is kept drier, because the larvae can’t survive in dry soil. Sticky traps catch the adults that are already flying.
Fungus gnats usually come from damp potting soil, not drains. Small flies around sinks and drains are more often drain flies, which need the organic buildup cleaned out.
Yes, repotting into fresh potting soil and a clean pot removes most eggs and larvae. Let the new soil dry between waterings so they don’t come back.
Fungus gnats are dark, slender flies that hover around houseplants, while fruit flies are tan with rounded bodies and gather around ripe food. Where the flies cluster usually tells you which one you have.
