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Pests

Tiny flies around your plants? How to deal with fungus gnats

4 min read · October 11, 2026

Fungus gnats are small dark flies that hover around houseplants. The adults are mostly a nuisance, but the larvae live in damp potting soil and can nibble at roots, especially on seedlings and young plants.

Why you have them

The usual cause is soil that stays moist for too long. Gnats lay eggs in damp soil, and the larvae feed on fungi and decaying material there. Overwatering is the most common trigger.

A simple plan

1. Let the soil dry out. Water less often and let the top two inches dry between waterings. This is the most effective step, because larvae need moisture.
2. Catch the adults. Hang or place yellow sticky traps near the plants. They also tell you whether things are improving.
3. Water from below. Set pots in a tray of water for a while, so the top layer of soil stays dry.
4. Add a dry top layer. A thin layer of coarse sand or fine gravel on top makes it harder to lay eggs.
5. Treat the larvae. Products containing Bacillus thuringiensis israelensis (often sold as BTI or “mosquito bits”) target the larvae and are generally considered safe around people and pets when used as directed. Follow the label.

Prevention

• Use fresh, good-quality potting mix, and don't reuse old soil from plants that were unhealthy.
• Make sure every pot has drainage and empty saucers after watering.
• Quarantine new plants for a couple of weeks and check the soil surface.