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Black Fly

Black Fly Control

How To Control Black Fly

Black flies, also known as buffalo gnats and turkey gnats, are persistent and irritating pests that swarm around humans and other animals. Found in large parts of the United States, black flies can be a major public health hazard in some areas. Adult black flies are most active during the summer months and bite mammals to feed on blood but can cause serious irritation by crawling into the ears, eyes, nose, or mouths of affected host animals. On cattle, horses and other livestock the ears seem to be the favorite feeding location. Black fly biting can be so severe in the upper Midwest and Northeast regions of the United States that outdoor activities like fishing, kayaking and hiking must be avoided.

Black flies are members of the Diptera order and there are 255 identified species in North America. Adult black flies are small (5-15 mm), dark with short legs, broad wings and have a humpbacked shape. While most species are black, yellow and orange species have been identified. Eggs are pale white and laid in a single group of 200-500 after females take a blood meal. Hatching occurs in 4-30 days depending on the species and environmental conditions. Hatched larvae mature through 4-9 stages in flowing water over 1-6 months and usually overwinter in this stage. Larval "drift" can occur resulting in pupae developing downstream of where prior black fly development occurred. Adult black flies emerge from pupae ready to mate, feed and lay the next generation of eggs.

Complete control of black flies is difficult to achieve, but there are a variety of steps one can take to mitigate and manage black fly populations. The following are just a few:

  1. Identify and monitor breeding habitat. Remember, black fly larvae require flowing water to survive, so small-scale damming can help to limit adult black fly populations from developing. Timing is crucial for the success of this treatment, so consult with a local conservation/extension service about timing in your area.
  2. Remove detritus from nearby bodies of water. This reduces suitable habitat for black fly larvae and limits adult black fly populations.
  3. Apply Bacillus thurengiensis israelensis (Bti) to egg-laying sites in the form of Mosquito Dunks or Aquabac (for large application areas). Bti is a bioinsecticide used for larval control of black flies. Larvicides like Bti should be applied throughout the season when black flies are active for best results.
  4. Wear light-colored clothing. Darker colors seem to attract black flies more so than white, off-white and tan colors, although there is minimal scientific research to support this.
  5. Use repellent sprays on animals and yourself if black flies are present. HOMS Insect Repellents are excellent for personal use and ARBICO Organics Holistic Fly Defense is formulated for use on horses and other animals.

More Information:

Photo courtesy of Clemson University Department of Entomology, Soils & Plant Sciences, Cooperative Extension Service.

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