Cliff Sadof, Entomology Department, Purdue University
If you are noticing small black flies around your house plants you could be
watering them too much. Two kinds of flies, called fungus gnats and shore flies
can thrive on continuously damp soils. To prevent these problems, allow your
soil to dry between watering.
Shore flies superficially resemble house flies. As the name implies they are found on the shore lines of ponds where they feed on algae. In your house plants adults and larvae feed on algae that grows when you overwater the plants. Shore flies are mostly a
Fungus gnats are more slender and gnatlike. They feed on fungi that grow on soil. Occasionally the maggots will also feed on plant roots spreading disease. For greenhouse growers fungus gnats can be a serious pest.
For more information consult this website: http://www.entomology.umn.edu/cues/inter/inmine/Fliesc.html
Click on the small image to view a larger image.
Shore Fly and Fungus Gnat
Photo courtesy of: Jack Kelly Clark, University of California
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