Dozens of feedlot and dairy operators have called David Taylor wondering how to control flies that are irritating the heck out of their cattle and taking big bites out of their billfolds.

“The first question I always ask: Do you know what kind of fly you’re trying to deal with? Ninety-plus percent of the time, they don’t know if their problem is the stable fly, face fly, horn fly or house fly,” said Taylor, a research entomologist for USDA.

Bayer Animal Health technical services Veterinarian Larry Hawkins noted that this issue is beginning to change as operators see profits literally sucked out of their cattle, which can suffer weight-gain losses of up to 1 lb. per day if stable flies aren’t controlled.

But Hawkins still finds that many producers can’t properly identify each of the four main fly culprits, and they don’t know how each one affects cattle.

“It’s not uncommon to hear something like: We aren’t seeing many flies on our cattle, so why are our cattle being bothered so badly?” he said.

Researchers have determined that since the bite of a stable fly is so doggone painful, it only takes three to five flies on one leg of an animal to cause serious consequences.

“That’s the economic threshold; that’s when you definitely start losing production,” Hawkins said.

That’s why it’s so important for producers to be able to clearly determine what kind of fly is causing trouble.

“Each one has a unique response in terms of control,” said Taylor, who emphasized that “sanitation is your best friend” to keep populations of stable flies in check.

Mound manure and remove weekly; ensure that all feedlots and dairies have good drainage and water troughs aren’t leaking; pick up spilled feed and leftover hay; clean up vegetation following mowing operations; and make sure that feed is covered and dry.

“I’ve seen huge, huge numbers of stable flies developing where silage leaked out of a tube and got rained on,” Taylor said.

And don’t forget one critically important aspect about the stable fly: they are “highly unpredictable,” he stressed. “We kind of joke that every time we think we know what they are doing, they do something else. They exploit every little mistake we make when it comes to larval developmental sites.”

Stable flies are developing in post-harvest vegetable, sugar cane and pineapple residue in Australia, Brazil and Costa Rica, respectively, said Taylor, who added: “We were getting stable fly numbers in excess of 1,500 flies per animal associated with the pineapple fields.”

Because stables flies are so adaptive, Taylor recommended that feedlot and dairy operators start looking at possible development sites outside of cattle confinement areas, including crop residue in nearby fields.

Taylor and Hawkins also suggested that producers work closely with neighbors and others, including entomologists and animal health sales representatives, to develop a unified control plan.

“Since stable flies don’t know property lines, working as a group is critical if you want to improve a problem,” Taylor said.

Insecticides can play an important role in an integrated fly management program at feedlots and dairies, according to Cornell University veterinary entomologists. Control options include space sprays, larvicides, residual premise sprays and whole-animal sprays.

Treatment of building surfaces and fence posts with residual sprays should be used sparingly because high levels of resistance to these insecticides are now common, according to the Cornell researchers.

A newly released ultra-low volume, mist-type spray may allow operators to control stable flies during outbreaks, Taylor said.

“A mist spray could work well during a situation like this, but the goal, of course, is to avoid an outbreak,” he said. “However, they occasionally happen with even the best sanitation, so a premise mist might be your best option.”

When stable fly numbers are high and cattle are huddled up, Hawkins said, someone equipped with a backpack sprayer could spray the legs of as many cattle as possible and then put a column of mist above the animals.

“This is a tool for stable fly control that wasn’t previously available,” he said.

Regardless of what insecticide is being used, Hawkins encouraged producers to carefully read and follow label instructions. More information is available at