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Flies do more than annoy

Hoosier Perspectives: Implement fly control on the farm now to prevent infections and diseases.

Allison Lund, Indiana Prairie Farmer Senior Editor

June 17, 2024

2 Min Read
close-up of flies on a cow
TIME TO TREAT: If this is a sight on your farm, you have a problem on your hands. It is time to choose a fly control method and get this situation under control before your herd is affected. Ron Lemenager

It’s no surprise that flies are a nuisance on the farm, especially when they seem to keep landing in the same spot on your leg no matter how many times you swat them away. But the dangers for your livestock expand beyond a minor annoyance.

Now is the time to get a head start on fly control measures before they pose a threat. Plan to apply a pour-on insecticide, set up a self-applicator or begin mixing an insect growth regulator into your animals’ mineral. Find which control method works for you and implement it before it is too late.

Health concerns

You may have found yourself in the situation of waiting too long to begin fly control — when you can’t walk from one end of the barn to the other without feeling at least five fly bites. That may seem like a lot, but cattle can carry hundreds of flies with them throughout the day.

The economic threshold for controlling horn flies is 200 flies on the cow — 200 flies! Some cattle can have upward of 1,000 flies tagging along with them each day. Just that threshold of 200 flies equals about 0.4 pint of blood lost each day.

“That’s 50 pints of blood per animal per season, and that’s just at the economic threshold,” says Ron Lemenager, beef cattle specialist and professor of animal sciences at Purdue.

If those 200 flies can do that much damage, just imagine the blood that would be disappearing off that animal if 300, 500, even 1,000 flies were present without any control methods in place.

Stable flies take this problem a step further. They suck blood from animals, but they also can transmit anaplasmosis.

“The stable fly will eat one big meal a day on one cow, but tomorrow it may be on a different cow, and anaplasmosis is a blood-transmitted disease,” Lemenager explains. “We do have cases of anaplasmosis in the state [of Indiana].”

Face flies cause another host of problems. The face flies do not bite and suck blood like horn and stable flies, but they do eat secretions around the nose and eyes. Through this, they can transmit the bacteria that causes pink eye.

“Every year, producers who don’t control their flies and stay on top of that pink eye situation can end up with some calves that lose part or all of their eyesight,” Lemenager says.

Take control

While these effects of flies may not be seen immediately, they are already commencing for producers who have not yet acted. Early summer is the time to determine your fly control measures and set them in motion.

If the flies in your barn or around your pasture are starting to annoy you, then they may already be causing problems in your herd. Instead of swatting at them and darting back into the house after chores, consider the health of your herd and develop a fly control strategy.

“If you can control flies of all sorts, then that helps minimize issues,” Lemenager adds.

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About the Author(s)

Allison Lund

Indiana Prairie Farmer Senior Editor, Farm Progress

Allison Lund worked as a staff writer for Indiana Prairie Farmer before becoming editor in 2024. She graduated from Purdue University with a major in agricultural communications and a minor in crop science. She served as president of Purdue’s Agricultural Communicators of Tomorrow chapter. In 2022, she received the American FFA Degree. 

Lund grew up on a cash grain farm in south-central Wisconsin, where the primary crops were corn, soybeans, wheat and alfalfa. Her family also raised chewing tobacco and Hereford cattle. She spent most of her time helping with the tobacco crop in the summer and raising Boer goats for FFA projects. She lives near Winamac, Ind.

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