Fungus Gnats on Bonsai: Overwatering Is the Real Problem

Eliminating Fungus Gnats by Fixing Watering

Rowena's indoor bonsai has fungus gnats. She waters and mists daily per instructions.

Diagnosis

Gnats indicate soil stays too wet—roots are rotting. Larvae feed on decaying roots. Daily watering is almost certainly excessive.

Solution

• Water no more than twice weekly (unless plant wilts).
• Remove loose soil and surface rocks.
• Place ½-inch raw potato slices on soil surface; they attract larvae. Discard after 1 day. Repeat until no larvae.

Dry soil stops gnats; root rot kills the tree. Prioritize drying.