Could wet soil surface be causing fungus gnats?

Soil stays moist on top. Overwatering. High humidity. Fix: Let top 2 inches of soil dry between waterings Bottom water instead of top watering Cover soil with sand or diatomaceous earth to block egg-laying

Could infested soil from bag be causing fungus gnats?

Just opened a new bag of soil. Flies appeared within days of potting. Fix: Freeze soil before use or buy from reputable brands

PestsModerate

Fungus Gnats in Cannabis Soil

Fungus gnats are tiny flying insects whose larvae eat cannabis roots. Adults are annoying but harmless — the larvae in the soil do the real damage.

What it looks like

●Small black flies hovering around the soil surface
●Flies fly up when you touch the plant
●Seedlings wilting or stunted (larvae eating roots)
●Tiny translucent larvae in top inch of soil

Quick diagnostic checks

1Yellow sticky traps catch adult flies immediately

2Mosquito Bits (BTI) kill larvae in 2-3 days

3Hydrogen peroxide drench (3 ml H2O2 per liter water) kills larvae instantly

Causes ranked by likelihood

1. Wet soil surface

Most common

Signs

●Soil stays moist on top
●Overwatering
●High humidity

Fix

✓Let top 2 inches of soil dry between waterings
✓Bottom water instead of top watering
✓Cover soil with sand or diatomaceous earth to block egg-laying

2. Infested soil from bag

Common

Signs

●Just opened a new bag of soil
●Flies appeared within days of potting

Fix

✓Freeze soil before use or buy from reputable brands

⚠️When to worry

Gnats alone rarely kill an established plant but can destroy seedlings fast. Fix within a week.

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