April 6, 2005 — Stable flies can be a significant pest to livestock grazing in Midwest pastures, but there are ways to minimize the problem, according to Kansas State University (K-State) Research and Extension scientists.
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 (ADG) of [a] 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.”
“Currently, sanitation is the most important method of on-site reduction of stable fly populations in livestock operations,” said Joel DeRouchey, a K-State animal scientist. “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.”
K-State research identified the areas around round hay bales as primary breeding sites 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 U.S. Department of Agriculture (USDA) grant to study stable fly management on pastures.
Frequent cleaning or moving of feeding sites in pastures can reduce residue buildup, the scientists said. For confined animal feeding operations (CAFOs), 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. Research is lacking on the effectiveness of different management practices, but practical recommendations include:
• Move the feeder between feedings.
• Roll out hay in different locations throughout the pasture.
• Avoid rolling out poor quality or rotted hay that will not be eaten.
• Grind hay to help prevent sorting by the animals, thus decreasing waste.
• Avoid overfeeding, regardless of feeding method. This prevents trampled hay, which becomes habitat for stable flies once mixed with manure.
• Make sure there is adequate drainage to keep moisture from accumulating around the feeder. (Runoff from these sites should not enter open surface water, since it could jeopardize water quality.)
“If the residue can’t be minimized, proper cleanup and removal are necessary,” DeRouchey said. “Fly production peaks in May and early June; therefore, the site should be cleaned and waste disposed of before April 15.”
Management options for cleaning sites include piling and composting the residue, scraping and removing residue from the site, and burning the residue.
“Certain limitations based on costs associated with labor, type of feeding practice, equipment available for site cleanup and the actual feeding site location will influence what management practices can be used to minimize stable fly production,” DeRouchey said. “Producers should be aware of the impact that feeding sites have on stable fly production, which, in turn, affect the performance of livestock in pastures and grasslands.”
For more information on stable flies, view MF-2662, “Managing Stable Fly Production at Pasture Feeding Sites,” online at www.oznet.ksu.edu/library/entml2/MF2662.pdf, or visit a local county or district Extension office.
— This article was adapted from a release written by Crystal Rahe of K-State Research and Extension, which supplied the report.
