Eliminating Fungus Gnats: The Alcohol Solution

Eliminating Fungus Gnats: The Alcohol Solution

Fungus gnats swarming your plants? These tiny flies indicate overwatering and rotting roots. Here's a proven, inexpensive fix using rubbing alcohol.

Why They Appear

Fungus gnats breed in constantly moist soil where fine roots are decaying—just like they're attracted to rotting fruit. The adults are nuisance fliers; the larvae damage roots.

Step-by-Step Eradication

1. Empty all saucers immediately. Remove standing water.
2. Let plants dry thoroughly. Wait until pots feel light when lifted.
3. Water with alcohol solution: Mix 1 cup 70% isopropyl alcohol per quart of water. Water normally with this solution—it kills larvae on contact.
4. Cut watering in half. Going forward, water only when soil is dry 2–3 days, and always empty saucers after 1 hour.

Prevention

The alcohol treatment breaks the cycle, but consistent dry-down between waterings prevents recurrence. Fungus gnats cannot survive in properly managed soil.

Expert advice from Darlene, houseplant specialist.