Fungus gnats: tiny black flies.

Annoying but mostly harmless. They're telling you the soil is too wet.

The fix

1. Stop watering. Let the top 2 inches dry completely.
2. Place yellow sticky traps near the pot to catch adults.
3. For persistent cases, top-dress with BTI mosquito bits.
4. Long-term: water less often, and only when needed.

Why peace lilies get gnats

Fungus gnats breed in consistently damp organic potting mix. Peace lilies like evenly moist soil, so they are easy to overwater just enough to invite gnats. The flies are annoying, but the bigger message is that the surface of the soil is staying wet too long.

Adults vs larvae

Sticky traps catch adult flies, which reduces the swarm, but larvae live in the top layer of soil. To actually end the cycle, dry the surface between waterings and use BTI if the problem persists. BTI targets gnat larvae and is commonly sold as mosquito bits or dunks.

A three-week plan

1. Week 1: let the top soil dry more than usual and add sticky traps.
2. Week 2: water only if the plant needs it, using BTI-treated water if larvae continue.
3. Week 3: replace traps and check whether new adults are still appearing.

Do not overcorrect

Do not let the entire root ball become bone dry for long periods just to kill gnats. Peace lilies can wilt hard when kept too dry. Aim to dry the top layer while keeping the deeper root zone from staying soggy.

Check the pot and mix

If gnats keep returning, the pot may be too large, the mix may be compacted, or drainage may be poor. A peace lily in a heavy decorative pot with no drainage is almost always harder to keep gnat-free. Repot into a draining pot and a lighter mix if the soil smells sour or stays wet for a week.

When gnats are a root warning

Gnats alone are not root rot, but gnats plus yellow leaves, drooping in wet soil, or a sour smell should make you inspect the roots. The same wet conditions that breed gnats can also deprive roots of oxygen.

How to water while treating gnats

Water deeply when the plant actually needs it, then let the pot drain and allow the top layer to dry again. Small frequent sips keep the surface damp, which is exactly what larvae prefer. A deeper, less frequent rhythm is usually better for both roots and gnat control.

Surface barriers

A thin layer of horticultural sand or fine pumice can make the surface less inviting for egg laying, but it is not a substitute for correct watering. Do not pile on a thick decorative layer that traps moisture or hides the soil from your checks.

What success looks like

Adults should decline first as traps fill. Larvae take longer because they are in the soil. If you still see new adults after three weeks, repeat the BTI cycle and recheck whether the pot is too wet, too large, or poorly drained.

Common treatment mistakes

• Using sticky traps but never changing the watering pattern.
• Letting the plant sit in saucer water after treatment.
• Adding a thick decorative top layer that keeps moisture hidden.
• Repotting into an even larger pot, which keeps more soil wet.

When to repot

Repot if the mix is sour, compacted, or staying wet despite improved watering. Choose a pot only slightly larger than the root ball and use a mix that drains well while still holding some moisture.

After repotting, skip decorative moss on top of the soil. It can look tidy, but it keeps the surface damp and makes it harder to see when the mix is drying.