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Fungus Gnat - Diptera: Sciaridae



Authors as Published

Eric Day, Department of Entomology, Virginia Tech


Image 1 Fungus Gnat Fungus gnat. David Cappaert. Michigan State University. Bugwood.org.


Fungus gnats are flies that are common household pests. They are slender, mosquito-like, and delicate with long legs and one pair of clear wings. Size: About 1/8 inch (3-4mm). Color: Grayish to black.


They are usually seen flying at windows and around house plants. Homeowners may notice these small flies when watering potted plants.

Life Cycle

The larvae of fungus gnats live in moist soil and feed on decaying organic matter. These conditions are abundant outside in the fall season and nearly year round in potted plants.

Type of Damage

Although the larvae rarely attack healthy plant roots, they may nibble at a few roots and reduce the vitality of house plants.

Cultural Control

Residual insecticides (use an aerosol) will help to control these pests. Removing old papers, boxes, books, and clothes from the attic to basement will help remove food and hiding places. Moth crystals placed in boxes in the attic will also help.Control of fungus gnats in the house is relatively simple. Adult fungus gnats are attracted to
moist, organically rich soil. Examine all house plants for "over-watered soil." Allowing the soil to dry out for several days (or longer) is probably the best control of these pests. The larvae live in the top layer of soil. If the top layer of soil becomes dry, the larvae will die and the adults will not have a place to lay their eggs

Interesting Facts

Larvae feed on highly organic soils and can damage the roots of bedding plants, African violets, carnations, poinsettias and foliage plants.


Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.


Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Interim Administrator, 1890 Extension Program, Virginia State University, Petersburg.


May 13, 2011

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