High populations of horse flies, a stubborn and difficult biting fly to control, have caused problems for Texas livestock producers this year, said Dr. Sonja Swiger, AgriLife Extension entomologist, Stephenville.
Swiger said reports of horse fly infestations are higher than she’s ever experienced during her 11-year career.
The numbers should begin to wane because temperatures have risen to more inhospitable levels. But the pest can resurge with later summer rains or in the fall.
Like mosquitoes, only female horse flies bite because they need the host’s blood for egg production. But unlike mosquitoes, horse flies cut the host and consume blood as it drips from the wound.
Swiger said horse flies typically stay in shaded areas, such as along tree lines. They consume carbohydrates, such as nectars and honeydew, but females will range from cover to hunt hosts once a day.
There is no available data focused on the effectiveness of pours designed to curtail horse flies. But pyrethroid, especially synthetic pyrethroid-based pours, have been shown to provide temporary relief. And most synthetic pyrethroid products are not labeled for horses.
The best defense for horses is to move them from the infested area, into a barn or to cover them with lightweight summer sheets designed to stop biting flies and mosquitoes, she said.
Swiger noted another concern about higher-than-normal horse fly numbers – anthrax. The species are known vectors of the disease, but the extent of their role in spreading the disease is unknown. http://bit.ly/2Kv4M7m
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