How to Get Rid of Fungus Gnats for Good

Priya Hollis · Sep 22, 2026 · 4 min read

Quick answer

Those tiny black flies around your houseplants breed in damp soil. Break the life cycle and they disappear within a few weeks.

Fungus gnats are small, dark flies that hover around pots and windows. Adults are mostly a nuisance, but their larvae live in the top layer of soil, where they feed on organic matter and can damage the fine roots of seedlings and young plants.

Because the life cycle takes a few weeks, any treatment has to run long enough to catch each new generation.

Let the soil dry out Trap the adults Treat the larvae Stop new infestations

1 Let the soil dry out

Larvae need moist soil to survive. Letting the top few centimetres dry out between waterings is the single most effective step. Bottom watering, where the pot sits in a tray of water for a short time, keeps the surface drier.

2 Trap the adults

✓Yellow sticky traps placed just above the soil catch flying adults
✓Traps also show you how bad the problem is and whether it is improving
✓Replace them when they are covered

3 Treat the larvae

✓Products containing Bacillus thuringiensis israelensis (Bti), sold for mosquito control, kill larvae when mixed into watering water
✓A layer of coarse sand or fine grit over the soil surface makes it harder for adults to lay eggs
✓Beneficial nematodes sold for fungus gnats can be watered into the soil

4 Stop new infestations

Fresh bags of potting mix are a common source. Store compost sealed, avoid overwatering newly potted plants, and check new plants before bringing them home.

This is general gardening information. Results depend on your climate, soil, and conditions. Follow label directions for any fertiliser or treatment, and check whether plants are toxic to pets or children before bringing them home.

🔓

Keep reading

Watch a short ad to unlock the rest of this guide — free, no account needed.

Keep reading

Other plant problems people ask about