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Stop Fungus Gnats
One visible adult usually means more are developing in the soil

Fungus gnats don't stop at one fly.

A female fungus gnat can lay dozens of eggs in moist potting mix. Because generations can overlap, new adults may continue emerging after treatment begins — the cycle doesn't break on its own. This is how you break it.

Is this you?

  • Tiny flies lift off every time you water
  • They gather at windows, not the fruit bowl
  • The soil never seems to fully dry out
Get the full guide Not sure it's gnats? Identify first
Or jump straight to the 7-day plan
  1. Identify
  2. Treat
  3. Prevent
Indoor houseplant on a windowsill with damp soil where fungus gnats breed
Damp soil like this is the nursery

The whole fix

Confirm it, find the source, manage moisture, trap and treat

In that order. Skip identification or the source and you're just delaying the next generation, not stopping it. The 7-Day Starter Plan turns this into a day-by-day checklist.

See the full 7-day plan
  1. 1

    Confirm it's actually fungus gnats, not fruit flies or drain flies.

  2. 2

    Find the likely breeding source — a consistently damp nearby pot is common, but check other damp organic sites too.

  3. 3

    Adjust watering so the mix dries appropriately for that specific plant — not the same rule for a succulent as a seedling.

  4. 4

    Stand yellow sticky cards at soil level to monitor and catch adults.

  5. 5

    If soil moisture and traps alone aren't enough, use a Bti product labeled for fungus gnats, following the label.

3–4 weeks
approximate egg-to-adult time indoors
~2 weeks
approximate time larvae feed in the mix
Several weeks
typical time to complete control, not days

First: confirm the pest

Wrong diagnosis, wasted week.

Fungus gnats commonly breed in moist potting mix, though other damp organic sites are possible. Fruit flies commonly breed in fermenting fruit and trash. Drain flies breed in the buildup inside drains. Treating the wrong pest won't solve the underlying problem. Three questions will sort it — or see the full comparison.

Close-up of a fungus gnat on moist potting soil
Identify the pest1 / 4

Where do you see them most?

Four quick questions

Why they keep coming back

You're fighting a life cycle, not a few flies

Full stage-by-stage detail: the fungus gnat life cycle. Wondering how they got here at all? See the causes.

The fungus gnat life cycle, illustrated in three stages Stage one: eggs laid in wet soil hatch within days. Stage two: larvae feed underground for about two weeks, invisible to sticky traps. Stage three: short-lived adults emerge, fly up when disturbed, and lay the next batch of eggs — restarting the cycle unless it's broken. THE CYCLE REPEATS — UNLESS YOU BREAK IT 01 EGG Hatches in days 02 LARVA Feeds ~2 weeks INVISIBLE TO TRAPS 03 ADULT Lays the next batch
01

Eggs in wet mix

Females lay in moist organic soil. Eggs hatch in a few days.

02

Larvae underground

White maggots with black heads feed for about two weeks. Traps miss them completely.

03

Short-lived adults

Adults are weak fliers. Kill them and the next wave still emerges from the pot.

Methods that work

Stack three attacks at once

See every treatment
Let the soil dry for fungus gnat control

Most important · Ongoing

Let the soil dry

Fungus gnats breed in constantly wet mix. Let the top 1–2 inches dry between waterings and you remove their nursery.
Yellow sticky traps for fungus gnat control

Adults · 5 minutes

Yellow sticky traps

Place yellow cards at the soil surface to catch egg-laying adults. Traps monitor the infestation — they do not finish it alone.
Bti (Mosquito Bits) for fungus gnat control

Best-supported larvicide · Per product label

Bti (Mosquito Bits)

Bacillus thuringiensis israelensis is a bacterium that specifically targets fly larvae. Use a product labeled for fungus gnats and follow its rate and reapplication instructions.
Hydrogen peroxide drench for fungus gnat control

Optional — use cautiously · 10 minutes

Hydrogen peroxide drench

A diluted peroxide drench is a common household suggestion, but extension guidance on it is mixed. Not part of the default plan — read the cautions before using it.
Prevention that actually sticks for fungus gnat control

Keep them gone · Habit change

Prevention that actually sticks

Bottom watering, a sand or grit top-dress, sterile mix, and empty cachepots. Keep monitoring for a couple of weeks after adults stop appearing.

Prevention

Keep them from coming back

Water from below

Bottom watering keeps the surface drier so females have nowhere useful to lay.

Cover the soil

A half-inch of coarse sand or grit after larvae are down makes egg-laying harder.

Quarantine new plants

Nursery mix is a common hitchhike. One sticky card for a week before they join the shelf.

Read the full prevention guide · Natural methods, rated

Quick answers

Fungus gnat guides

Still wondering

Common questions

Q01 What are fungus gnats?

Fungus gnats are small, dark, mosquito-like flies whose larvae live in moist potting mix and feed on fungi, decaying organic matter, and sometimes fine roots. Adults are weak fliers that hover around houseplants and windows. They are harmless to people but can damage seedlings.

Q02 How do I get rid of fungus gnats?

Let the top 1–2 inches of soil dry between waterings, set yellow sticky traps at soil level to catch adults, and treat larvae with a Bti product such as Mosquito Bits or Gnatrol if moisture control isn't enough. Complete control usually takes several weeks.

Q03 How do I kill fungus gnats?

Kill adults with yellow sticky cards and larvae with Bti or beneficial nematodes, and stop new eggs by letting the soil dry. Killing only the flying adults won't end the infestation.

Q04 What do fungus gnats look like?

Adults are about 1/8 inch long, slender, and dark gray to black with long legs and antennae. Larvae are translucent white worms with a shiny black head, up to about 1/4 inch.

All questions