Pest Severity: Medium ⚠️ Contagious

Fungus Gnats: How to Identify & Treat Fast

Fungus gnats are small, gray-to-black mosquito-like insects (1/8 to 1/10 inches long) commonly found in indoor plants. Adult gnats are mostly a nuisance, but their larvae feed on plant roots and organic matter in soil, potentially causing serious damage to young or vulnerable plants. The larvae are translucent white with distinctive black heads and can leave slime trails on the soil surface in heavy infestations.

Spread speed

Fast

Recovery time

14 days

🔍 Symptoms

Main Symptoms

! Small dark flying insects resembling mosquitoes hovering around plants
! Translucent white larvae (5mm) with black heads visible in soil
! Slime trails on soil surface in severe infestations
! Yellowing leaves without obvious cause
! Stunted or slow growth
! Wilting despite adequate watering
! Root damage visible when plant is unpotted
! Seedlings or cuttings failing to thrive

Visual Signs

Small gray-to-black mosquito-like insects around 1/8 to 1/10 inches longTranslucent white larvae with distinctive black heads (5mm long)Slime trails on soil surface (in heavy infestations)Yellowing leavesStunted growthWilting plantsRoot damage in vulnerable or young plants

Affected parts: RootsWhole plant

❓ Possible Causes

→ Overwatering creating persistently moist soil conditions
→ Organic-rich potting mixes that retain excessive moisture
→ Poor drainage in containers
→ Presence of decaying organic matter in soil
→ Bringing infested plants indoors
→ Using contaminated potting soil
→ High humidity combined with wet soil
→ Lack of air circulation around plants

💊 Treatment

⚡

Quick Fixes

~7 days

Step 1

Remove top 1-2 inches of infested soil and replace with fresh sterile potting mix

Step 2

Apply hydrogen peroxide solution (1 part 3% peroxide to 4 parts water) as soil drench

Step 3

Set up multiple yellow sticky traps around affected plants immediately

Step 4

Stop watering for 3-5 days to kill larvae and eggs

Step 5

Apply BTi mosquito dunk solution for immediate larvae control

Materials needed:

Yellow sticky traps3% hydrogen peroxideAquarium sandPyrethrin-based insecticide

🌿

Organic Treatment

~14 days

Step 1

Allow soil to dry completely between waterings to disrupt larvae lifecycle

Step 2

Apply food-grade diatomaceous earth (1/4 inch layer) on soil surface

Step 3

Water plants with BTi (Bacillus thuringiensis israelensis) solution using mosquito dunks

Step 4

Sprinkle cinnamon powder on topsoil as natural fungicide

Step 5

Place yellow sticky traps near plants to capture adult gnats

Step 6

Introduce beneficial nematodes (Steinernema feltiae) to soil for larvae control

Materials needed:

Coarse sand or gravelYellow sticky trapsDiatomaceous earthBacillus thuringiensis israelensis (BTI)Cinnamon powderBeneficial nematodes

🔬

Expert Treatment

~21 days

Step 1

Conduct soil moisture audit and adjust watering schedule to prevent overwatering

Step 2

Apply commercial-grade BTi larvicide through drip irrigation or soil drench

Step 3

Release predatory mites (Hypoaspis/Stratiolaelaps) and rove beetles (Dalotia coriaria)

Step 4

Implement integrated pest management with yellow sticky cards for monitoring

Step 5

Apply beneficial nematode solution (minimum 50 million nematodes per plant)

Step 6

Treat soil with diatomaceous earth barrier and natural fungicides (cinnamon/chamomile)

Step 7

Improve drainage and aeration with perlite or sand amendments if needed

Step 8

Monitor population weekly using sticky trap counts and adjust treatments accordingly

Step by Step

1
Stop overwatering immediately and allow top 1-2 inches of soil to dry
2
Apply Bti product (Mosquito Bits or Gnatrol) as soil drench following label instructions
3
Place yellow sticky traps horizontally at soil surface to monitor and trap adults
4
Remove any standing water from saucers or trays
5
Introduce beneficial nematodes to soil for biological control
6
Apply hydrogen peroxide solution (1:4 ratio) as soil drench if infestation is severe
7
Add 1/2 inch layer of sand or diatomaceous earth on soil surface
8
Repeat Bti treatment every 5-7 days for 2-3 weeks to break lifecycle
9
Monitor population with sticky traps and continue until no adults are caught for one week

🧪 Solutions

🌱 Natural Solutions

✓ Bacillus thuringiensis israelensis (Bti) - Apply as soil drench (e.g., Mosquito Bits, Gnatrol) to kill larvae
✓ Beneficial nematodes (Steinernema feltiae) - Parasitize and kill larvae in soil
✓ Hydrogen peroxide solution (1 part 3% H2O2 to 4 parts water) - Kills larvae and eggs on contact
✓ Yellow sticky traps - Place horizontally at soil level to catch egg-laying adults
✓ Apple cider vinegar trap - Mix equal parts vinegar and water with dish soap to trap adults
✓ Neem oil soil drench - Disrupts larvae development
✓ Diatomaceous earth - Sprinkle food-grade DE on soil surface
✓ Chamomile or cinnamon - Natural fungicides that eliminate gnats food source
✓ Bottom watering - Keeps soil surface dry to discourage egg-laying