Confirmed Fungus Gnats? Here’s How to Treat Them

Nov 04, 2025

Sticky traps alone won’t solve fungus gnat pressure. Real control comes from a clear sequence: adjust cultural practices, monitor accurately, and hit larvae where they live. The formula is simple: dry the surface, track adult trends, and treat the soil to break the cycle.

Step 1 — Cultural Corrections

Allow a light surface dry-down between irrigations
Eliminate easy breeding sites by clearing algae, spilled media, and debris in drains and floor joints
Remove wet pockets—saucers, under benches, cracked concrete, drain lines
Improve drainage patterns so the top layer doesn’t stay perpetually damp

Step 2 — Monitors That Tell the Truth

Yellow sticky traps at the soil line show whether adult pressure is rising or falling
→ Horiver Sticky Traps – Yellow - Monitoring & Trapping
A few raw potato slices on suspect pots confirm whether larvae are active at the interface

Combining adult trends with quick larval spot checks is the fastest way to decide whether to extend nematode cadence, tighten irrigation intervals, or expand predator releases.

Step 3 — Biological Knockdown

Entonem (Steinernema feltiae) is the standard for sciarid (fungus gnat) larvae in protected crops and interiorscapes. Infective juveniles move through the water film in the substrate, enter larvae via natural openings, and release symbiotic bacteria that kill the host within roughly 24–48 hours. New juveniles develop inside and disperse, extending impact in the same wetted volume. The approach is residue-free, compatible with broader IPM, and does not drive resistance because the mode of action is biological, not chemical.
→ Entonem (OMRI Approved)– Nematode for Fungus Gnat Control

How to apply nematodes so they deliver:

Drench in low light (early or late in the day or under cloudy conditions)
Keep the tank or bucket gently agitated so nematodes don’t settle at the bottom
Remove fine filters (≈50 mesh / 0.3 mm) that can strain them out
Apply with moderate pressure
After treatment, keep the substrate evenly moist for three to five days so they can move and find hosts
When adult counts remain high or new seedlings are entering the space weekly, repeat applications every two to three weeks until trap trends break; once numbers stay low, shift to a maintenance rhythm matched to turnover such as utilizing Entomite-M and/or Entonem only when repotting or bringing in new plants.

Step 4 — Build Staying Power in the Top Layer

After nematodes knock back larvae, add predators that live where adults deposit eggs:

Entomite-M (Stratiolaelaps scimitus) — soil-dwelling predatory mite that hunts fungus gnat larvae and thrips pupae
→ Entomite-M – Predatory Mite for Fungus Gnat
Atheta coriaria (rove beetle) — highly mobile, flying predator that patrols across substrate and hardscape, great for large greenhouses or set-ups with hard to treat nooks and crannies.
→ Atheta – Rove Beetle for Root Aphid & Sciarid Control

Step 5 — What Improvement Looks Like

Trap counts trend down week over week
“Mystery wilt” between waterings fades
Young plants regain pace
The root zone becomes a less hospitable place for eggs and newly hatched larvae, and biological allies—not chemical residues—are doing the daily work

Tools That Fit the Job

Entonem (Steinernema feltiae) — frontline larval control via drench.
Entomite‑M (Stratiolaelaps scimitus) & Atheta coriaria — long‑term soil protection.
Horiver Yellow Sticky Traps — trend adult activity and verify progress.

FAQs: Fungus Gnat Treatment & Action Steps

If I have fungus gnats, do I need to throw out all my soil?

Not neccesarily. Fungus gnats can be controlled without discarding soil. The key is breaking the life cycle in the media. Beneficial nematodes (Steinernema feltiae) and predatory mites (Stratiolaelaps scimitus) target larvae where they live—so you can treat the soil instead of replacing it.

Do I have to repot my plants to get rid of fungus gnats?

Not usually. Repotting is only necessary if the soil is severely compacted or waterlogged. For most cases, cultural corrections (dry-down cycles, sanitation) combined with biological controls will solve the problem without disturbing roots.

Will fungus gnats go away on their own?

No. Fungus gnats persist wherever moisture and organic matter remain. Without intervention, populations often increase. Expect continued pressure unless you change environmental conditions and treat larvae in the soil.

How long do fungus gnats take to go away using beneficials?

Beneficial nematodes start killing larvae within 24–48 hours. Visible improvement—fewer adults on sticky traps—usually appears in 7–10 days. Combined with Entomite_M expect to see minimal fungus gnat development after 2 weeks, if pressure does not recede within this time frame, apply a second dose of Entonem. For heavy pressure, repeat nematode applications every 2–3 weeks until trap counts stay low.

Is there a quick-fix spray for fungus gnats?

Surface sprays may kill adults temporarily, but they don’t reach larvae in the soil—the real source of damage. For lasting control, use biologicals like (Entonem) for larvae and (Entomite-M) for ongoing soil protection, paired with (Horiver yellow) for adult monitoring.

Does Entonem work for me if I’m a small home grower?

Yes. Entonem is easy to apply with a watering can or small sprayer. It’s residue-free and safe for houseplants, pets, and people. For ongoing prevention, pair nematodes with Entomite-M and sticky traps.

Could I just use Entomite-M and sticky traps instead of nematodes?

For light pressure or preventive care, Entomite-M plus sticky traps is typically all you need. For active problems with larvae already in the soil, nematodes provide faster knockdown. Combining both gives the strongest program.

Does this scale for small home setups and large facilities?

Yes. Nematode drenches work with watering cans/small sprayers or injection setups. Predators scale from a few containers to full benches. Sticky traps provide universal feedback at any scale.

What about large-scale growers?

Large-scale operations benefit from these same beneficials, but will need to scale them to their particular set-up. For consulation with our experst, reach out on live chat on the bottom right hand corner of our site or fill out our contact us form.

Entonem (OMRI Approved)– Nematode for Fungus Gnat Control drenches for larval suppression
Entomite-M – Predatory Mite for Fungus Gnat and Atheta – Rove Beetle for Root Aphid & Sciarid Control for long-term soil protection
Horiver Sticky Traps – Yellow - Monitoring & Trapping for adult monitoring

This combination scales easily for greenhouses, nurseries, and more.