How do I get rid of fungus gnats in my houseplants?
Why they appear and how to stop them
Fungus gnats thrive in consistently moist soil rich in organic matter. The adults are tiny, dark, and fly around the plant; the larvae live in the top layer of soil and feed on fungi and decaying matter, sometimes damaging roots. To control them, you must target both stages.
First, reduce watering. Let the top 1–2 inches of soil dry out between waterings. This kills many larvae and makes the environment less inviting. Second, trap adults with yellow sticky cards placed near the soil surface. Third, treat the soil with a biological control: mosquito dunks (containing Bti) soaked in water and used for watering, or beneficial nematodes (Steinernema feltiae) applied as a soil drench.
Step-by-step treatment
Start by removing the top inch of soil and replacing it with fresh, dry potting mix. Then water only when the soil is dry. For severe infestations, you may need to repot into clean mix and sterilize the pot.
If you prefer a homemade trap, mix a little apple cider vinegar with a drop of dish soap in a small bowl and place it near the plants; adults are attracted and drown. However, this only catches adults, so combine it with soil treatments.
- Let soil dry out between waterings.
- Use yellow sticky traps for adults.
- Apply Bti dunks or beneficial nematodes to soil.
- Replace top inch of soil with fresh, dry mix.
- Avoid overwatering and soggy saucers.
Common mistakes
- Overwatering is the root cause; simply spraying adults won't solve the problem.
- Using hydrogen peroxide or cinnamon as a soil drench; these are not reliably effective and can harm beneficial microbes.
- Ignoring saucers and cachepots where water collects and larvae can breed.
