More Flies Found Earlier on Cattle

Flies Present Earlier Than Normal, Thanks to Positive Fly Breeding Conditions

Russ Quinn
By  Russ Quinn , DTN Staff Reporter
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Horn flies on the belly of a cow. Fly season has come earlier than normal in many parts of the Midwest. (DTN file photo)

OMAHA (DTN) -- Bob Birdsell has seen more flies than normal on his cow-calf pairs this spring. The Stanberry, Missouri, farmer/cattle producer chalked it up to his region of northwestern Missouri having some decent moisture as the growing season started.

"I did notice it was an early start to fly season this year," Birdsell told DTN.

More insects are being seen earlier this growing season thanks to a decent breeding season for flies, according to entomologists. There are different management practices to limit pests, but an issue with controlling pests on livestock is on the horizon.


Cassandra Olds, Kansas State University Extension livestock entomologist, said flies have made an early appearance this spring in the Western Corn Belt. While contrary to what most people think, flies can have a successful breeding season during times of lower levels of rain.

Flies have an amazing reproductive capacity compared to other pests, she said. Ticks, for instance, can be affected by environmental issues from the last two to three years.

Flies are on the opposite end of the spectrum and really only need just a few weeks of decent weather for their breeding season, Olds noted.

"Flies just need a source of food and water, the right humidity levels and some place to lay eggs," Olds said. "If it good for even just a few weeks, they can go crazy."

Olds said the three main types of flies found on cattle on pasture are horn flies, stable flies, and face flies. All three pests need to be controlled to prevent economic losses in livestock production.


Horn flies are among the most common, as well as economically important, insect pests of cattle on pasture.

Economic losses are estimated at more than $1 billion annually in the United States, according to South Dakota State University (…). Research from Nebraska has shown calf weaning weights were 10 to 20 pounds heavier when horn flies were controlled on the cattle.

Horn flies are about half the size of normal flies or about 3/16 of an inch long, according to SDSU. They are found on the backs of cattle and migrate to the belly of cattle during the heat of the day.

Horn flies penetrate the skin of cattle to suck blood and horn flies may take 30 to 40 blood meals during the course of a day.


Stable flies are similar to horn flies as they, too, feed on blood. The difference is they mainly feed on the front legs of cattle, Olds said.

These flies are about the same size as a house fly, but darker in color. These pests are found in pastures, feedlots and dairies and they love decaying organic matter, such as wet hay.

Cattle often react to stable flies by bunching together and stomping their feet. This can disrupt grazing patterns and Nebraska research indicates reductions in weight gains from 0.2 to 0.4 pounds per day for grazing steers, according to SDSU.


Face flies are larger and darker than house flies. They cluster around animals' eyes, mouths, and muzzles to feed on mucus secretions.

Face flies cause irritation to eye tissues, which can lead to disease transmission, such as pinkeye.

The height of the face fly season is normally late July and August, but with an increased number of flies this spring in the Midwest, cattle producers are reporting pinkeye cases already.


Another type of fly that can become a significant pest for pastured livestock such as cattle and horses in some areas of Canada and the U.S. is horse flies.

South Dakota State University Extension Entomology Field Specialist Patrick Wagner wrote in a past online post: "Horse flies have the ability to inflict a very painful bite and draw large amounts of blood."

They are larger than stable or horn flies, 1/2 an inch to 1 1/4 inches long with a robust body covered with small hairs, he wrote, adding they can vary in color, "with many being black, grey, or brown and some having patterns of blue, green, or yellow. Most species are multicolored with stripes on the abdomen and thorax." When they emerge in early summer, "Much like mosquitoes, female horse flies require blood meals in order to develop eggs."

Wagner added, "Horse flies primarily feed on larger animals, including cattle and horses. They mostly rely on visual cues to seek out hosts, searching for large, dark, moving objects. Horseflies are capable of consuming large amounts of blood, leading to animal stress and reduced weight gain. They can also be disease vectors and potentially cause further harm to affected livestock."

University of Missouri Extension entomologists said horse flies are "probably the most severe fly pests of cattle on Missouri pasture and range" and have posted how to protect cattle from them, including how to build horse fly traps or a treadle sprayer, at…. See also from the University of Kentucky….


Birdsell said he battles pinkeye nearly every year with his cow-calf herd. He uses fly control products such as pour-on insecticides, mineral with fly control and in the past also used fly-control ear tags.

"We got to the point we needed to do something about the pinkeye, so we worked with our vet to vaccinate our cattle against pinkeye and that has really helped," Birdsell said.

Iowa State University Beef Specialist Erika Lundy-Woolfolk for southwestern Iowa based in Greenfield, Iowa, said she has also heard from cattle producers in her region that flies are especially thick early in the grazing season. This is leading to more cases of pinkeye in cattle.

The management of flies is an important undertaking due to economic. Lundy-Woolfolk said among the most popular form of control of insects would be sprays/pour-ons and ear tags against flies.

Using these products according to the label is key for success as fly ear tags are often applied too early in the grazing season, she said. Typically, grass turnout/pre-breeding vaccination time is generally before fly populations have reached the threshold where negative effects occur.

"So, during a normal year, the fly tags have already lost some effectiveness before peak fly season has occurred," Lundy-Woolfolk said.


Sprays and pour-on insecticides can be effective in helping to control flies, but these products require reapplication on a regular basis, which can be a challenge, she said. Some cattle producers will also use back rub or dust bags as a method of fly control.

Lundy-Woolfolk said another option is feed additives added to mineral supplements to control flies. Adding garlic salt, for example, is becoming more popular to help control fly populations, she explained.

Olds said she gets questions quite a bit about using garlic to control flies. Some producers use it and say it works, but they might be using other management practices which might be controlling the flies, she said.

"Consensus between us entomologists is it doesn't harm (cattle) but it probably doesn't work (to control flies) either," Olds said.


Much like plants becoming resistant to different herbicides, there's a major concern of entomologists that pests such as flies are becoming resistant to insecticides. Olds said this should also be a worry for livestock producers.

Companies that manufacture fly control products are not willing to spend the money to develop new chemical families to prevent these resistance issues, she said. So new products with different chemical makeups to combat insect resistance are limited.

Olds said the future of these fly control products is cloudy at best as some of these products are now more than 50 years old and insects are becoming more resistant to them. Even if everyone used these products correctly all the time, these resistance issues would still be present, she said.

Livestock producers might have to be willing to use different management techniques.

"I think we may have to fall back on practices producers utilized before pesticides," Olds said. "Sanitary practices such as limiting manure and feed waste are ways to limit amounts of flies."

Iowa State University Extension has a publication titled "Fly Control in Ruminants (…).

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Russ Quinn