January 2025 - Nematodes
Apr 01, 2026
How to Use Beneficial Nematodes for Fungus Gnats
Fungus gnats are one of the most common problems growers face during cooler months, when consistently moist soil creates the perfect breeding environment. In the January edition of Koppert Corner, published through GrowerTalks, we focused on how to get the most reliable results from beneficial nematodes.
While these recommendations are often shared with commercial growers, the same principles apply just as well to home growers and smaller setups, especially when dealing with persistent gnat problems.
One of the key points we emphasized is that nematodes act quickly, but for a limited period of time. After application, they actively control pests for a few days before their population declines. Because of this, consistent reapplication is essential when fungus gnat pressure is high.
We also highlighted a common issue with application. Even when the correct number of nematodes are used, applying them with too much water can push them too deep into the soil or out of the container entirely. Since fungus gnat larvae live near the surface, nematodes need to remain concentrated in the top layer of the growing media to be effective.
Choosing the Right Approach
In this month’s Koppert Corner, we pointed to Steinernema feltiae as the industry standard for fungus gnat control, particularly in cooler conditions. We also noted the growing use of Steinernema carpocapsae, which performs well in warmer soils and targets a broader range of pests.
As pest pressure decreases, transitioning to longer term solutions such as predatory soil mites can help maintain control and prevent future problems.
Applying Nematodes Effectively
The goal when applying nematodes is not to saturate the entire container, but to properly treat the surface layer where pests are active. A light, even application that keeps nematodes in the top portion of the soil produces the most consistent results.
During active problems, weekly applications are typically needed to keep fungus gnat populations under control. As pressure decreases, applications can be spaced out or replaced with preventative strategies.
What This Means for Growers
For home growers and hobbyists, the biggest takeaway is that nematodes are not a one time solution. Success comes from applying them consistently and using the correct technique.
By focusing on proper placement and timing, growers can achieve the same level of control that commercial operations rely on, without the need for chemical treatments.
The Bottom Line
The insights shared in Koppert Corner are designed to help growers get the most out of biological solutions. When applied correctly, beneficial nematodes remain one of the most effective and reliable tools for controlling fungus gnats at any scale.
This article is based on the Koppert Corner published in GrowerTalks and adapted for NaturalEnemies.com. To check out the original article, click here: Optimizing Nematodes; Rehydrating URCs; Growing Cut Campanula
Want more quick takes from Koppert's Corner on Grower Talks?
Type 3 Predatory Mites - March 2025
Cleaning Up Flowering Tropicals - April 2025
Pesticide Resistance Residues on Garden Mums - May 2025
Prevent Fungus Gnat Larvae - June 2025
Problematic Thrips on Poinsettas - July 2025
Mealybug Tag-team Takedown - August 2025
Preparing Perennials for Winter - October 2025
Just a dip won't do - November 2025
Gerbera and Hydrangea - December 2025
