Identification

• Fungus gnats are black-bodied, long-legged flies only about 0.2 mm long and half that wide. Unlike the wings of houseflies, fungus gnats have dark wings. They can be found in mushroom cellars, houseplants, vegetable gardens or anywhere peat moss is found.
  
  

Damage

• Fungus gnat adults are merely annoying, but their larvae eat the roots of plants to the point where the plant can at first wither and then die. Fungus gnat females can lay up to 150 eggs in her one-week lifespan.
  
  

Control

• Use drier soil to kill fungus gnats, as the females prefer to lay their eggs on moist soil. Mulch should be less than 3 inches thick to keep it too dry for larvae to survive. Microscopic nematodes that target fungus gnat larvae can be planted 600 to a square meter. The nematodes eat the larvae.