Identification

• Dark-winged fungus gnats are approximately 1/8 inch long and are grayish, brown or black in color. Hodgson and Lambert describe them as "mosquito-like," with long legs, antennae and a pair of wings. Dark-winged fungus gnats fly in a darting pattern and are attracted to light, where they will hover in groups. These pesky gnats are commonly found in your plants' soil and under the leaves. One way to determine if you have dark-winged fungus gnats is to shake your plant; if a bunch of little bugs fly away, you probably have fungus gnats.
  
  

Life-cycle

• The life-cycle of dark-winged fungus gnats is approximately four weeks. An impregnated adult female will lay 100 to 200 eggs that hatch in four to six days. Dark-winged fungus gnat larvae have black heads and white bodies. The 100 to 200 larvae consume decaying organic matter for approximately 15 days before they spin themselves into a cocoon. The adults emerge from these cocoons five to six days later, and the reproductive cycle begins all over again until the adults die in seven days.
  
  

Effects

• Thomas R. Fasulo and Frank R. Mead discuss on the University of Florida IFAS Extension's website that fungus gnats primarily feed off of "decaying organic matter," generally posing no threat. However, some species of the dark-winged fungus gnat have been known to infest alfalfa, cultivated mushrooms, pine seedlings, potatoes, red clover and wheat. They can also consume ornamental plants such as begonias, cacti and orchids to name a few. Should the dark-winged fungus infest a greenhouse or crop, they are capable of causing serious economic damage.
  
  

Prevention/Solution

• Fungus gnats thrive on moist soil conditions so avoid overwatering your plants, make sure to let the soil completely dry between waterings and use pots with adequate drainage. Make sure your house doesn't have any leaking plumbing either. Inspect all plants for fungus gnats before buying them and, if you are transplanting at home, make sure all old soil is thrown away and replaced with new, sterilized soil. Seal doors and windows to prevent fungus gnats from getting inside at night. Place yellow sticky traps on top of your plants' soil to catch any laid eggs. (Ref. 3)
  
  

Warning

• In severe dark-winged fungus-gnat infestations, such as crops or greenhouses, pesticides can rid the plant life of the destructive pests. Apply pesticides by drenching pots and spraying the foliage, plant beds and soil surfaces according to the manufacturers instructions. Pesticides will kill the larvae and eggs, but not the adult gnats. A natural way to kill the adults is use entomopathogenic nematodes or predatory mites, according to the University of Guelph. For serious infestations, a combination of both methods might be most effective.