How to Get Rid of Fungus Gnats in Houseplants

Fungus gnats are small flying insects that lay eggs in moist potting soil, and the way to get rid of them is to let the soil dry out between waterings and target the larvae in the soil. Adult gnats are a nuisance but mostly harmless, and the larvae are the part that can damage seedlings and stressed roots.

How do I know it is fungus gnats?

Tiny dark flies hovering around plants or the soil surface, especially when you water or move the pot. They are weak fliers. Larvae are thin, translucent, and live in the top layer of soil.

Why do I have them?

They are attracted to constantly damp soil and decaying organic matter. Overwatering is the most common reason.

Step 1: Let the soil dry out

Allow the top inch or two of soil to dry between waterings. Dry topsoil makes it hard for eggs and larvae to survive.

Step 2: Trap the adults

Yellow sticky traps placed near the plants catch adults and help you see how bad the problem is. They reduce adults but do not stop the larvae.

Step 3: Treat the larvae

Common options include:

• Bti products (often sold as mosquito bits or dunks), which target fungus gnat larvae when soaked into the soil. Follow the label.
• Watering from below so the top layer stays dry.
• A top layer of sand or grit to make the surface less inviting for egg laying.

Step 4: Repeat and be patient

The life cycle takes a couple of weeks, so treatments usually need repeating for several weeks to catch each new generation.

How do I prevent them coming back?

Water only when needed, use a well-draining mix, empty saucers, and avoid leaving damp organic debris on the soil. Check new plants before bringing them near others.

Related reading: How to save an overwatered plant, Best soil for houseplants