The mouthpart of an adult stable fly could take on the creepiest role in a sci-fi horror flick.

There are two sets of six incredibly barbarous, bayonet-shaped teeth. Adding to that, each tooth looks like a serrated butcher knife carefully handcrafted to inflict as much destruction—and misery—to their victims as possible.

Pain is one of the first words used by David Taylor to characterize the adult stable fly.

“They are very, very vicious biters. Their mouths look like clam shells full of teeth used for digging and prying,” says the U.S. Department of Agriculture research entomologist who’s been studying critters that inflict damage on cattle since the early 1980s.

Adds Larry Hawkins: “Their sabers look like something out of Star Wars, something that you would use to drill under the Hudson River.”

Taylor and Hawkins, a technical services veterinarian at Bayer Animal Health, agree that cattle aren’t the only sufferers from stable flies; the bank accounts of cattle producers and feeders can languish as well.

“It only takes three to five stable flies on a front leg to cause economic impact,” emphasizes Taylor, who notes that total U.S. losses are about $2.2 billion annually, including $226 million for feeders.

Explains Hawkins: “When stable flies are biting, cattle huddle up in circles. The ones on the outside keep getting bit so they try to push to the middle of the crowd. Then, the ones pushed out fight to get back in.”

The cattle just keep fighting and fighting—instead of feeding and feeding.

Scientific studies (and subsequent economic modeling by Taylor and a team of university researchers) reveal that weight gains in feedlot cattle can suffer by up to 1 lb. per day during stable fly outbreaks.

That means a potential loss of 56 lb. over a typical eight-week stable fly season—or up to 56,000 lost pounds if you’re feeding 1,000 cattle.

To avoid such losses, Taylor and Hawkins recommend making feedlot sanitation priority No. 1.

Since stable flies lay their eggs in moist, rotting vegetative material mixed with cattle urine or manure:

  • clean up hay rings, spilled feed along feed bunks and cast-off silage from the silage pit;
  • mound manure and then remove from the lot at least once every two weeks;
  • ensure water troughs aren’t leaking and feedlots have good drainage;
  • clear manure and other loose materials along fence lines, including windrows of vegetation left behind from mowing and trimming.

“You can get tremendous numbers of stable flies out of very small mistakes,” Taylor stresses. “Ninety percent of the feedlot can be clean, but if you have one spot with rotting feed, that can produce literally thousands of stable flies per square meter.”

Since the critters can fly several miles, Taylor and Hawkins recommend that cattle feeders work with as many neighbors as possible in developing a unified strategy.

Additionally, Hawkins says, there are a number of effective “premise” insecticides that can be sprayed on such things as fence posts. “Usually, stable flies come from the exterior of feedyards and attack the perimeter cattle first. If they get a blood meal, they go rest on a nearby post.”

Starting in 2016, feedlot and dairy operators have another tool to help control stable fly populations—DeltaGard®, an “ultra-low volume” product that can be easily distributed out of a backpack sprayer.

“Since this is the first season, there’ll be a learning curve, but we believe those using DeltaGard in confined areas will be able to kill off big populations of adult stable flies if they spray about twice a week,” Hawkins says.

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