Adult shore flies are small, dark-grey flies (approx. 1/8 inch long), resembling fruit flies, with robust bodies, and short legs and antennae. They have five distinctive whitish spots on their gray wings. Shore flies are easily distinguished from fungus gnats, which are slender and fragile in appearance, with long antennae.
Adult fungus gnats are mosquito-like in body shape, about 1/8 inch long, with long legs, a clear pair of wings, and long antennae. Fungus gnats are weak fliers and are frequently observed resting on the media in the pot or running over the foliage or other surfaces.
Both shore flies (Scatella stagnalis) and fungus gnats are small, dark colored flies found in moist environments in the greenhouse. Shore flies and fungus gnats feed on algae and are found in areas where algae are growing. Shore flies do not feed on plants, however, adult shore flies deposit fly spec on foliage that may be unsightly to customers.
Fungus gnats are general feeders and can injure a number of flower crops grown in the greenhouse. Adults are primarily a nuisance however, larvae feed on plant roots, fungi and decaying organic matter and tunnel into the crown and stems of plants. The feeding damage creates wounds that allow soilborne pathogens to enter and can kill plants.
See fact sheet: Fungus Gnats and Shore Flies
