Keep Your Operation Free of Fungus Gnats and Shore Flies

Spring production is a common time for fungus gnats and shore flies in the greenhouse as warm, wet conditions are favorable for their development. With their short life cycle, it doesn’t take long for populations to build quickly. While adult fungus gnats are primarily only a nuisance, the larvae feed on plant roots and stems, allowing soilborne pathogens to enter and cause disease. Shore flies (adults and larvae) don’t typically feed on plant tissue – instead favoring algae or decaying organic matter – but the adult fly is known to effectively vector several soilborne pathogens, such as Thielaviopsis, Fusarium and Pythium spp.

What to Watch For

Adult fungus gnats are dark, mosquito-like insects, with long legs, one pair of clear wings, and a Y-shaped vein in the wing pattern. Larvae are legless, thread-like and transparent. Infected plant symptoms may appear as sudden wilting, loss of vigor, poor growth, yellowing and foliage loss. Because adults are attracted to moist, organically rich soil, it’s a good idea to allow soil to dry out for several days.

Shore Fly
Shore fly. Rechcigl, Syngenta
Fungus Gnat
Fungus gnat. Jim Baker, North Carolina State University,

Adult shore flies are slightly larger than fungus gnats and resemble a small housefly with stockier bodies. They have shorter legs and antennae than fungus gnats and are also stronger, faster fliers. Shore fly larvae are white, wedge shaped and do not have distinctive heads. Shore flies are typically spotted where water and algae accumulate and can be easily scouted by capturing them on yellow or blue sticky cards.

Disrupt Pests’ Lifecycles

Citation® insect growth regulator (IGR) can help control fungus gnats, shore flies and dipterous leafminers by preventing them from reproducing. As an IGR, Citation:

  • Disrupts normal larval growth and development.
  • Interferes with the formation and release of essential insect molting hormones.
  • Disrupts pests’ lifecycles so they are unable to advance to the next stage of development and subsequently die.

Application Recommendations

Apply as a spray or drench to all surfaces where insects may breed. This includes the potting media surfaces, bench tops, undersides of benches and the areas under benches that may be contaminated with potting media or algae. Repeat applications on 7 to 14-day intervals rotating with a different mode of action after three consecutive applications to minimize re-infestation.

To learn more about how to keep your operation free of fungus gnats and shore flies with proven control, visit

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