Fungus gnats
Small black gnats flying around houseplants.
Updated on 2026-07-17
Overview
Fungus gnats (Sciaridae) lay eggs in moist substrate. Larvae feed on mycelium and can damage young roots. Adults are harmless but annoying.
Differential diagnosis
Fast black gnats on the soil = fungus gnats. Whitefly = small white moth under the leaves.
Natural remedies
Top the soil with 1 cm of coarse sand or expanded clay: it blocks egg-laying.
Treatments
Bacillus thuringiensis israelensis (Bti) in the watering elminates larvae.
Prevention
Do not keep substrate constantly moist.