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Photos by Debbie Roos, Agricultural Extension Agent. May 2009Description and Biology of the 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.
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Close-up of damaged stems. Larval feeding insde the stems cause the seedlings to collapse at the soil line. |
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This shot reveals at least five larvae feeding inside the stem. |
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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. |
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The adult fungus gnats are tiny but noticeable as they fly about. |
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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.
This page last updated January 15, 2010.