Identification

• Fungus gnats are tiny flies that grow in the potting soil of houseplants. Adult fungus gnats grow to lengths of 1/8 inch and have antennae. The larvae of fungus gnats feed on organic matter in potting soil, such as fungi and algae. Fungus gnat larvae are see-through wormlike creatures and are usually found in the top 2 inches of potting soil.
  
  

Time Frame

• Fungus gnats are most often noticed during the late part of fall and early winter. These pests are also more common in houseplants as they age because potting soil degrades as it ages, making it more moist and attractive to fungus gnats. Plants use less water during periods of cold weather, keeping potting soil moist for most of the day, which encourages fungus gnat development and growth.
  
  

Effects

• Most people notice fungus gnat infestations when they move their plants or water them. Moving your houseplant with fungus gnats causes them to stir and fly in clouds. This is often a nuisance for the homeowner. Fungus gnats do not bite or feed on plant foliage. This pest often feeds on small portions of plant roots, but does not usually damage an otherwise healthy houseplant.
  
  

Control

• Changing your watering habits is important to the control of fungus gnat infestations. Potting soil that remains very wet helps fungus gnats thrive. Placing sticky traps may eliminate some fungus gnats, but will not eliminate them completely because their eggs in the soil will hatch. Controlling larval development is the most effective means of fungus gnat control. Soil drenches are available to eliminate and control fungus gnats in houseplants.