Fungus Gnats in Potted Plants: Causes and Fixes

Tiny black flies rising from your pot plants are probably fungus gnats.

The short answer

Fungus gnats breed in moist potting soil rich in organic matter, and larvae feed on fungus and roots. Let the top layer of soil dry between waterings, avoid overwatering, remove standing water in saucers, use well-draining mix and cover soil with sand or gravel. Yellow sticky traps catch adults. Persistent infestations may need repotting with fresh soil.

Causes

• Overwatering and constant dampness.
• Rich, organic potting mix.
• Water in saucers.
• Fresh plants brought home.

Fixes

1. Let the top soil dry between waterings.
2. Empty saucers.
3. Place sticky traps near plants.
4. Cover soil with a layer of sand or gravel.
5. Repot with fresh, well-draining mix if severe.

Prevention

• Inspect new plants.
• Water thoughtfully.
• Keep dead leaves cleared.

When to call a professional

If the problem is widespread, keeps returning or you are unsure what you are dealing with, a professional inspection will save time and avoid wasted effort.

Frequently asked questions

Do gnats harm plants?

Larvae can damage roots, especially seedlings.

Do they bite?

No.

Is neem helpful?

Some use diluted neem. Follow label instructions.

How long to get rid of them?

Several weeks of dry-soil routine.

This guide is part of IPest's complete resource on fly control. For identification help, prevention and treatment options, see our full fly control guide for Bangalore.