Eliminating Fungus Gnats from Office Plants: Drying Out Soil and Alcohol Treatment

Cause: Overwatering

Fungus gnats breed in constantly moist soil. Even if the surface feels dry, the lower root zone stays wet.

Solution

1. Water the soil with straight rubbing alcohol (isopropyl) to kill larvae on contact. It won’t harm roots.
2. Then let the plant dry out completely—soil dry and pot light—before watering again.
3. Empty saucers 2 hours after watering (turkey baster works).
4. When repotting, use 1/2 soil + 1/2 perlite for better aeration and drainage.

Prevention

Keep the soil dry between waterings. Gnats won’t return if the environment isn’t a swamp.