Houseplant Soil Insects: Fungus Gnats and Others—Sanitation and Control

Two-year battle with tiny black/white insects, worms in soil of 100+ houseplants. Malathion, soil replacement, root rinsing failed. Recent losses to spider mites and chlorine sensitivity.

Primary Pest: Fungus Gnats

• Tiny black flies (2 mm) hovering over soil.
• Larvae feed on fungi/root hairs; indicate overwatering.

Integrated Management

• Quarantine infested plants.
• Reduce watering—let soil dry between waterings.
• Yellow sticky traps for adults.
• Diatomaceous earth on soil surface.
• Repot with fresh, sterile mix; clean pots, wash hands.
• Isolate new plants one week before introducing.
• Discard heavily infested plants immediately.

Overwatering is the root cause. Correct cultural practices break the cycle.