Stable flies pose risk in pastures, too

MANHATTAN, Kan. – Stable flies can be a major pest to livestock grazing in Midwest pastures, but there are ways to minimize the problem, according to Kansas State University Research and Extension scientists.
Sure signs. Stable flies mainly bite on an animal’s legs. Foot stomping and tail switching are clear signs of stable flies’ presence.
Cattle also try to protect themselves from painful bites by standing in water, lying with their legs tucked beneath them, and bunching up at the corners of pastures.
For the cattle industry, the issue is about economics as well as about the health and well-being of the animals.
“Weight gain performance in both pastured and confined cattle is affected by the presence of stable flies,” said Ludek Zurek, a medical and veterinary entomologist with K-State Research and Extension.
“In an 84-day trial, researchers in Nebraska recorded a reduction in average daily gain of half pound per day in cattle that received no insecticide application compared to cattle that had an insecticide application at least three times per week.”
“Stable flies don’t develop in pens where cattle continuously tread over manure. The most common larval sites are old manure under fences, poorly drained areas and other areas avoided by cattle.”
Breeding ground. K-State research identified the areas around round hay bales as a primary breeding site for stable flies.
Because cattle congregate in those areas, manure accumulates around those feeding sites. By spring, the waste (mixture of cattle manure, soil and hay) is an ideal site for development of stable fly larvae.
“At this time, there are no effective insecticides that can be used for management of stable flies in this environment,” Zurek said. “There are promising results from laboratory tests on controlling stable flies but they haven’t been tested in the field yet.”
Field testing is scheduled for this spring at K-State as part of a USDA grant to study stable fly management on pastures.
Prevention. Frequent cleaning or moving of feeding sites in pastures can reduce residue build-up, the scientists said.
For confined animal feeding operations, cleaning pens seasonally and scraping under fences, in addition to spreading manure, can be effective control measures.
For temporary feeding sites or more urban settings, DeRouchey and Zurek recommend producers prevent stable fly production by reducing or eliminating the breeding habitat.
DeRouchey said that producers should first prevent large accumulations of manure and moisture at the feeding site.
What you can do. Research is lacking on the effectiveness of different management practices, but practical recommendations include: