January 2026 - Fungus Gnats and Shoreflies
Apr 01, 2026
How to Control Fungus Gnats and Shoreflies in Wet Winter Conditions
Cool, dark, and consistently wet conditions create the perfect environment for pest problems in early-season production. In the January edition of Koppert Corner, published through GrowerTalks, we focused on two common issues that often appear together: fungus gnats and shoreflies.
While these pests are frequently grouped together, they behave differently, and understanding those differences is key to choosing the right control strategy.
Knowing What You’re Dealing With
In this month’s Koppert Corner, we emphasized that correct identification is the first step.
Fungus gnats are easy to recognize by their long legs and mosquito-like appearance. Their larvae live in the growing media and feed on plant roots, which can lead to reduced growth and increased risk of disease.
Shoreflies, on the other hand, resemble small houseflies with shorter legs. They do not typically damage plants directly, but they thrive in wet environments and can spread pathogens as they move across crops.
Even though shoreflies do not feed on roots, they still need to be managed, especially in propagation and high-moisture environments.
Why Fungus Gnats Cause More Damage
Fungus gnats are the primary concern because of their lifecycle.
In this month’s discussion, we highlighted that adult gnats can lay hundreds of eggs, which hatch within a few days. The larvae remain near the surface of the growing media, feeding on root hairs and young roots, exactly where plants are most vulnerable.
Because of this, populations can increase quickly if not addressed early, especially in consistently moist conditions.
Building a Complete Control Strategy
Effective control requires targeting both adults and larvae at the same time.
We outlined a combined approach that includes reducing adult populations while also treating the root zone where larvae develop. This dual strategy helps break the lifecycle and prevent populations from rebuilding.
For fungus gnats, this means focusing on the top layer of growing media where eggs are laid and larvae feed. For shoreflies, reducing algae and excess moisture plays a major role in limiting their habitat and food sources.
Consistency is key. Regular monitoring and repeated applications are what keep populations under control.
What This Means for You
For growers and retailers, the takeaway is to pay close attention to moisture levels and early pest activity.
If you are seeing small flies in your growing area, identifying whether they are fungus gnats or shoreflies will help you respond more effectively. Starting control early, before populations increase, will always lead to better results.
Managing moisture, monitoring consistently, and using a combination of control methods will help prevent these pests from becoming ongoing problems.
The Bottom Line
The insights shared in Koppert Corner highlight that successful control of fungus gnats and shoreflies starts with understanding their differences. By targeting the right life stages and maintaining a consistent approach, growers can reduce pest pressure and protect plant health throughout the growing cycle.
This article is based on the Koppert Corner published in GrowerTalks and adapted for NaturalEnemies.com. To check out the original article, click here: CAST Sneak Peeks; Rootzone Temps; Fungus Gnat, Shorefly Control
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
