Growing Small Farms: Darkwinged Fungus Gnat

Dark-winged fungus gnat larvae (maggots) can be serious pests in the greenhouse. The larvae feed on plant roots and stems and can severely damage transplants.

Control measures: Be careful to not overwater and if possible allow to dry slightly between watering.

Place yellow sticky cards horizontally at the soil surface to capture some of the adults.

The larvicide Gnatrol® is OMRI-listed and labeled for vegetable transplants. Gnatrol® contains Bacillus thuringiensis (Bt) subspecies israelensis as its active ingredient and is applied as a soil drench. (See Pesticide Use Guidelines).

Predatory nematodes and mites can be used to help control the gnats.

wilted seedlings

Damaged melon seedlings. Adult fungus gnats lay eggs on the soil near plant stems. The larvae feed on the roots and root hairs, eventually finding their way into the stem.

close-up of wilted seedlings

Close-up of damaged stems. Larval feeding insde the stems cause the seedlings to collapse at the soil line.

fungus gnat larvae inside stem

This shot reveals at least five larvae feeding inside the stem.

fungus gnat larvae

Fungus gnat larvae sometimes cling together, forming a snake-like line, and migrate in search of a new food source. Photo by Scott Welborn, North Carolina Cooperative Extension.

fungus gnat

The adult fungus gnats are tiny but noticeable as they fly about.

fungus gnat

Close-up of adult.

* These recommendations apply only to North Carolina. They may not be appropriate for conditions in other states and may not comply with laws and regulations outside of North Carolina. Certified organic growers should consult their certifier before using a new pesticide. Unless otherwise noted, these recommendations were current as of June 2009. Individuals who use pesticides are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage regulations and examine a current product label before applying any pesticide. For assistance, contact your county Cooperative Extension Service agent. The use of brand names and any mention or listing of commercial products or services in the publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned.

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This page last updated January 15, 2010.

North Carolina Cooperative Extension, Chatham County Center
P.O. Box 279, Pittsboro, NC 27312
919-542-8202

Website created and maintained by Debbie Roos, Agricultural Extension Agent.

URL: www.growingsmallfarms.org

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