Medium Severity 14 day treatment

Fungus Gnats in Houseplant Soil

Sciaridae

Fungus gnats live in moist potting mix and cause annoying swarms. Learn how to kill larvae and stop them for good.

Signs to Look For

  • Tiny flies near soil
  • Larvae in wet mix
  • Slow growth in seedlings
  • Worse after watering

Quick Fix

  1. 1 Let the top 1 to 2 inches of soil dry out
  2. 2 Use sticky traps to catch adults
  3. 3 Reduce watering frequency

Commonly Affects

Overwatered houseplants Seedlings Propagation trays Tropical plants Herbs

What fungus gnats actually are

The adults are those tiny flying bugs near your pot. The real problem is the larvae in the soil, feeding on fungus and soft roots.

Confirm fungus gnats

  • Adults hover around soil, not leaves
  • You see more after watering
  • Sticky traps catch many small black flies

Treatment plan that works

Step 1: Dry the top layer

Larvae thrive in wet soil.

  • Let the top 1 to 2 inches dry between watering.

Step 2: Trap the adults

Sticky traps reduce the next generation.

  • Place traps close to the soil surface.

Step 3: Target larvae

If infestation is heavy, consider:

  • BTI (mosquito bits) in watering can
  • A thin layer of sand or top dressing to reduce egg laying

Prevention

  • Avoid consistently wet soil
  • Use well-draining mix
  • Do not let old leaves rot on top of the soil

Frequently Asked Questions

Do fungus gnats harm plants?

Adults are mostly annoying. Larvae can harm seedlings and stressed plants by chewing soft roots.

Why do they keep coming back?

Because the soil stays wet and larvae keep maturing. You must interrupt the lifecycle for 1 to 2 weeks.

Are fungus gnats the same as fruit flies?

No. Fungus gnats stay near soil. Fruit flies are usually around food and drains.

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