Soil Pests: Grubs, Gnats

The pest eating your crop might be below the surface. Fungus gnats, shore flies, and root-feeding grubs do their damage in the media — here's how to identify soil pests and exactly how to get rid of fungus gnats and grubs naturally.

Soil pests attack from below, chewing roots, spreading root-rot pathogens, and weakening plants before you ever see a problem up top. Because they live in moist media where sprays and drenches struggle, the reliable fix is soil-dwelling biologicals.

How to identify soil pests

Fungus gnats are small dark flies hovering over the media, with translucent larvae in the top layer; shore flies are stouter with spotted wings and feed on algae; grubs are C-shaped larvae chewing roots. Watch for wilting, stunted rooting, and seedling loss despite proper watering.

Why soil pests are so damaging

Larvae feed on roots and root hairs and can carry diseases like Pythium, all while protected in wet media. Overwatering and algae fuel rapid build-up, and the adults you swat are just the visible tip of a larval population below.

How to get rid of soil pests naturally

Let the surface dry between waterings, monitor with yellow sticky cards, and apply soil biologicals — beneficial nematodes, predatory soil mites, and rove beetles — to attack larvae in the root zone. As a bonus, soil predators also catch thrips pupating in the media.

Beneficials that stop soil pests

• NEMAforce SF / SC / HB — beneficial nematodes matched to fungus gnats, shore flies, and grubs.
• STRATIOforce — predatory soil mites that eat fungus gnat larvae and thrips pupae.
• DALOTIAforce — rove beetles that patrol the media surface.

Ready to build a program? Shop the full Soil Pest Control collection.

Frequently asked questions

How do I get rid of fungus gnats and grubs?

Dry out the surface, monitor with sticky cards, and apply beneficial nematodes plus soil predators to kill the larvae in the media.

What are soil pests in plants?

Insects and larvae living in the growing media — fungus gnats, shore flies, grubs, and pupating thrips — that feed on roots and organic matter.

What causes fungus gnats?

Overly wet media, algae, and rich organic matter create ideal breeding conditions for fungus gnat larvae.

Do beneficial nematodes really work?

Yes — they actively seek out and kill larvae in the soil; match the nematode species to your target pest for best results.