Eliminating Fungus Gnats from Houseplant Soil

Identify the Pest

Tiny black flies hovering around plants are almost always fungus gnats. Adults are harmless; larvae in wet soil feed on fungi and roots.

Control Methods

• Dry out soil: Let top 1–2 inches dry completely between waterings.
• Surface barrier: Add ½ inch of sand, diatomaceous earth, or coarse coir to deter egg-laying.
• Potato slices: Place raw potato slices on soil; larvae congregate underneath. Discard daily.
• Bacillus thuringiensis (Bt): Apply to soil per label for larval control.
• Yellow sticky traps: Catch adults; reduces breeding.
• Red wine trap: Small glass of wine attracts and drowns adults.

Prevention

Use sterile, bark-free potting mix with perlite. Avoid overwatering. Quarantine new plants.