Arkansas Cattle Deaths Blamed on Swarms of Black Flies

A small pile of black flies, also known as a buffalo gnats or a turkey gnats, in a petri dish. ( University of Arkansas System Division of Agriculture photo by Kelly Loftin )

Swarms of black flies are impacting livestock farmers in Arkansas this spring, reports University of Arkansas Extension. The population explosion is to blame for the deaths of a bull and cow in Arkansas County and the closure of a nature center.

Black flies, part of the Simuliidae family, are also known as buffalo gnats or turkey gnats. They are blood-sucking feeders, and often fly around a person or animal’s heads, targeting eyes, ears and crawling in the hair. On cattle and horses, the ears are often a favored feeding location.

Cool, wet weather and ample running water seem to be a favorable environment for the pests to reproduce.

Between heavy rain and temperatures bouncing between the 40s and 70s in the last few weeks, “we’re seeing a bumper crop of black flies, likely as a result of floods in February and March,” says Kelly Loftin, Extension entomologist for the University of Arkansas System Division of Agriculture. “These are late winter, early spring pests that usually go away when temperatures warm above 80 degrees.”

Grant Beckwith, Arkansas County Extension, said a cattle producer in DeWitt lost a prize bull and cow to the flies – identified as southern buffalo gnats. He adds there have been reports of several horses and deer that might also be affected.

Livestock mortality is usually the result of acute toxemia or anaphylactic shock caused by the introduction of black fly saliva during massive feeding. Rarely, livestock can also die from blood loss causing deficiency in oxygen transport.

“Buffalo gnats are a fact of life down here,” Beckwith said. “The running joke is that the buffalo gnats will have you looking forward to mosquito season.”

“If a massive swarm attacks mammals or poultry, death is usually the result of anaphylactic shock or toxemia caused by a large influx of black fly saliva,” Loftin said. “It’s rare–but it has been observed—that livestock can die from being bled dry.”


How to Protect Livestock

These types of flies are daytime feeders and prefer outdoors. Farmer and ranchers can protect livestock by enclosing them in a shelter, if available.

Insecticides such as Permethrin sprays can be applied to livestock for short-term relief. Total coverage of the animal is important.

If neither of the first two measures are available, heavy smoke can help protect animals from the flies. This however, does not encourage much grazing.

The farmer that lost a cow and bull has since sprayed and used smoke to protect his herd.

Fans might also help discourage fly populations. Some poultry producers also report success with products containing Citronella oil, the Arkansas Extension sources say.

For human protection, the best measures include avoiding outside work during the day, and using repellents when outdoors. Wearing bright or light colored long-sleeve shirts, pants and fin screened netting over your head will prevent bites. If bites are found, sources say antihistamines and topical medications such as Cortaid, or similar products, can help with the itching.

Loftin said repellents containing DEET have shown mixed results and some data has demonstrated that botanical repellents containing geraniol are effective as well as repellents containing picaridin or IR3535. Clothing-only repellents containing permethrin, such as Permanone or Sawyer clothing repellent, will repel black flies but can only be applied to shirts, pants or hats and not to skin.