How to Get Rid of Fungus Gnats
Stop them from killing your houseplants. Learn to identify and eliminate these annoying soil pests forever.
Quick Answer: Fast Steps
1. Stop overwatering: Let the top 2 inches of plant soil dry out completely between waterings.
2. Deploy yellow sticky traps: Place them right above the soil of affected plants to catch flying adults.
3. Use a BTI root drench: Soak "Mosquito Dunks" in your watering can to kill larvae in the soil harmlessly.
4. Bottom-water your plants: Keep the topsoil dry so adult gnats cannot lay new eggs.
Fungus Gnats vs. Fruit Flies: The Crucial Difference
Many people waste weeks trying to catch fungus gnats with apple cider vinegar traps. Apple cider vinegar only works on fruit flies. Fungus gnats do not care about fermenting sugar; they care about the decaying organic matter and fungus in your wet houseplant soil.
Fungus Gnats (Bradysia spp.)
- Look like tiny mosquitoes, dark and slender.
- Clumsy, weak flyers.
- Hover close to houseplant soil and rest on leaves.
- Attracted to damp soil and light.
Fruit Flies (Drosophila)
- Tan or brown bodies, often with red eyes.
- Active, quick flyers.
- Hover around fruit bowls, drains, and kitchen trash.
- Attracted to vinegar, wine, and overripe fruit.
Step-by-Step Fungus Gnat Removal
1. Catch the Adults (Yellow Sticky Traps)
Adult fungus gnats only live for about a week, but a single female can lay up to 300 eggs in that time. You must trap the adults before they breed. Purchase small, yellow sticky traps (gnats are specifically attracted to the color yellow) and stick them directly into the soil of your houseplants.
2. Kill the Larvae (The BTI Method)
To permanently get rid of fungus gnats, you must kill the larvae eating your plant's roots. The safest, most effective method is using BTI (Bacillus thuringiensis israelensis), a natural bacteria commonly sold as "Mosquito Dunks" or "Mosquito Bits".
How to use BTI: Soak a Mosquito Dunk in your watering can overnight. Remove the dunk, then water your plants with this "tea". The BTI bacteria only affects the larvae of gnats and mosquitoes; it is completely harmless to plants, pets, and humans.
3. Change Your Watering Habits
Fungus gnats require perpetually moist topsoil to survive. If the top 2 inches of your soil are dry, the eggs will not hatch. Switch from top-watering to bottom-watering (placing the nursery pot in a bowl of water and letting the roots drink from the bottom up). This keeps the top layer of soil bone-dry, rendering it uninhabitable for gnats.
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