# Steinernema feltiae

> An entomopathogenic nematode applied as a soil drench whose infective juveniles enter fungus gnat larvae and thrips pupae and kill them with symbiotic bacteria.

- Canonical: https://genetixbay.com/knowledge/glossary/steinernema-feltiae.html
- Also written: beneficial nematodes, entomopathogenic nematodes, EPN, S. feltiae, nematodes
- Glossary category: Pests and diseases · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

*Steinernema feltiae* is a microscopic roundworm that parasitises insects living in moist soil. Its infective juveniles enter a host through natural openings and release symbiotic bacteria (*Xenorhabdus* species) that kill it within a couple of days. New nematodes breed inside the body and leave to hunt again. It is one of several entomopathogenic nematodes sold for crops; it works at cooler soil temperatures than many others.

## In practice

Growers mix the product in cool water and drench the medium, mainly against [fungus gnat](https://genetixbay.com/knowledge/glossary/fungus-gnat.md) larvae and soil-pupating [thrips](https://genetixbay.com/knowledge/glossary/thrips.md). Nematodes are alive and fragile: store them refrigerated, use them before the expiry date, apply in the evening or under low light, keep the medium moist for several days afterwards, and do not mix them with high-EC solutions or disinfectants. Repeat applications every one to two weeks during heavy pressure are common. They pose no known risk to plants, people or pets.

## Don't confuse with

- **Root-knot nematodes**: plant-parasitic nematodes that damage roots; a different group.
- **Bti**: a bacterial toxin that must be eaten by larvae.
- **Stratiolaelaps scimitus**: a [predatory mite](https://genetixbay.com/knowledge/glossary/predatory-mite.md) for the same pests.

## Related terms

[Fungus gnat](https://genetixbay.com/knowledge/glossary/fungus-gnat.md), [Thrips](https://genetixbay.com/knowledge/glossary/thrips.md), [Stratiolaelaps scimitus](https://genetixbay.com/knowledge/glossary/stratiolaelaps-scimitus.md), [Bti](https://genetixbay.com/knowledge/glossary/bti.md), [Biological control](https://genetixbay.com/knowledge/glossary/biological-control.md)

## Read more

- [Fungus gnats: the watering problem with wings](https://genetixbay.com/knowledge/pests/fungus-gnats.md)

## Sources

1. UConn IPM. Biological Control of Fungus Gnats. https://ipm.cahnr.uconn.edu/ipm-biological-control-of-fungus-gnats/
2. UC IPM. Pest Notes: Fungus Gnats (Publication 7448). https://ipm.ucanr.edu/legacy_assets/pdf/pestnotes/pnfungusgnats.pdf