Fungus gnats, or dark-winged fungus gnats, are flies in the order Diptera and the family Sciaridae. Most of the ones growers encounter are in the genus Lycoriella, Sciara, or Bradysia.

Adult fungus gnats are small, slender, and resemble mosquitoes more than common house flies. 

They have long, thin legs and beaded antennae. 

The most important characteristic for identifying them is a Y-shaped vein in the center of their wings. No other insect that looks anything like a fungus gnat will have that feature.

Their larvae are legless, primarily white, and have a shiny blackhead.

Larvae feed primarily on fungi but consume other organic material, including plant roots, if good fungi are unavailable.

Fungus gnats undergo complete metamorphosis, which develops through four primary stages – egg, lava (four instars), pupa, and adult.

Adult females lay around 150 eggs in moist potting soil or other media.

When the temperature is around 75°F, eggs hatch in about three days. The larvae take roughly ten days to develop into pupae. Approximately four days later, the adults emerge.

Adults live around ten days.

Fungus gnats are sometimes seen as nuisance pests, but they can transmit disease and visibly degrade plant quality.

In high enough numbers, they can even stunt or kill young plants.

The larvae are the only stage that damages plants and the stage in which to target them for control.

Monitor adult fungus gnats using yellow sticky cards placed just above the soil level.

Note that sticky cards are only for monitoring. You will not trap and kill enough of them to attain control.

The larvae require high moisture content to survive.

They tend to be found in the highest numbers in propagation houses and other humid/moist environments.

It’s best to prevent them from becoming established in the crop by using some combination of NEMAforce™ SF, Steinernema feltiae, DALOTIAforce™, Dalotia, or STRATIOforce ™, Stratiolaelaps.

Use NEMAforce™ SF, Steinernema feltiae as a knockdown for fungus gnat hotspots.

Both DALOTIAforce™, Dalotia, and STRATIOforce ™, Stratiolaelaps are very persistent in the soil and work well for fungus gnat prevention.