How can I get Rid of Fungus Gnats?

S. Gonzales

To get rid of fungus gnats of the Sciaridae fly family, one must first identify them. Differentiate fungus gnats from other flying pests by checking for the following:

Fungus gnats are attracted to warm, decaying plant remains.
Fungus gnats are attracted to warm, decaying plant remains.

  • Color. Fungus gnats are dark gray or black.
  • Length. They are usually 1/16 inch (about 1.6 mm) long, but certain species can grow up to 1/4 inch (about 6.4 mm).
  • Appendages. Their bodies are characterized by long legs, long antenna and very thin wings.
  • Hangouts. While indoors, they can be found near windows and light fixtures.
  • Movements. Fungus gnats often appear to be "running" along the ground or around potted plants.

Fungus gnats, as their name suggests, are attracted to fungus and warm, decaying plant remnants. They often pose problems for gardeners and owners of houseplants who tend to both indoor and outdoor plants. Orchid owners may especially find these tiny pests troublesome.

Plant caretakers may notice fungus gnats flying around their plants and then find that their plants bear damage like yellowing and wilting leaves. The larvae of fungus gnats are to blame for this damage, since they feed on seedlings and plant roots and strip them of the nutrients required for them to thrive.

For adult gnats that already fly within a home, practical devices like space sprays, pheromone traps and fly traps placed around the breeding ground or other attractive areas can work to rid the space of the gnats' presence. Hanging yellow sticky traps around the affected area can also help owners keep tabs on the fungus gnats' breeding cycles and alert plant owners of when more treatments are needed.

Bacteria treatments that utilize Bacillus thuringiensis israelensis to combat diptera, parasitic nematodes (Steinernema carpocapsae or Steinernema feltiae) and predatory mites (Hypoaspsis miles) are also suitable to be used within a greenhouse or atrium.

Having a houseplant turn into a breeding ground for gnats can be avoided by not over-watering the plant. Leftover moisture in potted soil makes the soil hospitable for gnat larvae to grow. Over-feeding a plant can also contribute to fungus gnat infestations, as the leftover organic matter acts as a food supply. Monitoring a houseplant's watering needs with a water meter and regularly repotting soil can help keep a houseplant safe from these pesky critters.

Controlling gnats outside can be made simple by identifying all breeding grounds and exposing them to light. Raking and turning over moist mulch, soil and other types of decaying organic matter exposes damp areas and dries them out by introducing them to direct sunlight and wind. The sunlight and wind then kill the fungus these gnats enjoy. Applying an organic pesticide to the affected area and reapplying it for especially heavy fungus gnat infestations should yield satisfactory results.

It should be noted that fungus gnat infestations in commercial buildings, such as offices, schools or restaurants, will need to be addressed on a much more serious level. Infestations in these places can sometimes require structural changes.

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Discussion Comments


I have been informed that I have fungus gnats. I have a 6yr. old small water pond that seems to have activity, since I have fish in the pond I'm concerned. The bamboo and various plants look healthy but there is a white powder and some specks all over the leaves. I itch and so do my dogs? Could there be a correlation? Help??

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