Plant-by-plant
How to get rid of fungus gnats in plants
Written by Mustafa Ayan Fact-checked against university extension/IPM sources Last reviewed: October 14, 2026
Direct answer
To get rid of fungus gnats in plants, treat the soil, where larvae live. Let the top 1–2 inches dry between waterings (less aggressively for seedlings and moisture-loving plants), trap adults with yellow sticky cards, and use a Bti product such as Mosquito Bits or Gnatrol in place of a watering. Repeat per the label and keep monitoring for weeks.
Start with the soil
Fungus gnat larvae live in the top inch or two of potting mix, so the fix is in the pot. Check the surface by finger: if it's still damp an inch down, hold off watering. Bottom-watering lets the roots drink while the surface stays dry. Empty saucers after 15–20 minutes.
Treat the larvae
Apply a Bti product to the soil, following the product label for amount, method, and reapplication. Use it as your watering for that pot, not on top of one. Beneficial nematodes are an alternative if you can get them fresh.
If you're still seeing a problem, repotting into fresh, well-draining mix and rinsing off as much old mix as the plant tolerates can remove many larvae, though it won't remove eggs on nearby surfaces.
Adjust for the plant type
- Tropicals and ferns: can't go bone dry, so water less often, use a chunkier mix, and top-dress with sand so the surface dries.
- Succulents and cacti: gnats usually mean the mix is holding too much water, so fix drainage and watering rather than drenching.
- Orchids in bark: judge dryness by pot weight, not by feel.
- Seedlings and cuttings: dry only the very top layer, and act early because larvae can damage small root systems.
- Edibles: follow product labels for use near food crops and avoid drenches close to harvest.
Monitor before you stop
Keep sticky cards out until they stay clean for a couple of weeks. A clean card doesn't prove larvae are gone, so check with a potato test if you're unsure.
Common questions
How do I get rid of fungus gnats in my plants naturally?
Let the soil dry between waterings, use yellow sticky traps, and use Bti, a naturally occurring bacterium that targets fly larvae. Cinnamon and essential oils have limited evidence.
Do I need to repot a plant with fungus gnats?
Not always. Repotting into fresh, well-draining mix can help if the old mix stays soggy, but you still need to manage watering and trap adults.
Are fungus gnats bad for my plant?
A light infestation rarely harms a mature plant. Heavy larval feeding can damage seedlings, cuttings, and stressed plants.