Fungus Gnats: Why They Show Up and How to Stop Them
Fungus gnats are tiny black flies around wet soil. They’re a symptom of overwatering. Let soil dry and use bottom watering.
They look like tiny fruit flies but hover around soil, not fruit.
How to Confirm
- Tiny black flies around pots
- They walk on soil surface
- Larvae (small white worms) in soil
- More active when soil is wet
Why They Show Up
- Overwatered soil
- Wet soil surface (top watering)
- Organic matter in soil decomposing
- Warm indoor temperatures
How to Get Rid of Them
Step 1: Stop Watering
Let top 1-2 inches dry completely.
Step 2: Bottom Water
From now on, water from the bottom.
Step 3: Yellow Sticky Traps
Place near soil surface. Catches adults.
Step 4: Cinnamon
Sprinkle on soil surface.
Step 5: Sand Layer
1/4 inch of sand on soil surface.
Step 6: Beneficial Nematodes
For heavy infestations.
Prevention
- Bottom water only
- Let top inch dry between waterings
- Don’t over-fertilize with organic matter
- Use fresh soil for new plants
Common Questions
Do fungus gnats harm plants? Larvae eat fungi and organic matter. They rarely damage roots.
Will they go away on their own? Only if you fix the moisture.
Can I use vinegar traps? Yes, but less effective than sticky traps.
Do they bite? No.
How long is their life cycle? About 3-4 weeks from egg to adult.
Can they spread to other plants? Yes. Isolate affected plants.