When it comes to controlling flies in cattle, Extension livestock specialists and veterinarians say variety can help.
Grant Dewell, Extension beef veterinarian with Iowa State University, suggests using “integrated pest management,” or a combination of strategies.
“There’s a lot of different options (for fly control),” he says. “I think we need to use multiple efforts in order to really do it.”
Dewell says many producers use fly tags, although they can supplement that with spray or pour-on treatment before and after the window during which fly tags work. Feed additives and back rubs or oilers help continue treatment.
David Hoffman, a University of Missouri Extension livestock specialist based in Cass County, says the variety approach also extends to mixing up the ingredients used to combat resistance in the insects.
“The best strategy or approach is to alternate between active ingredients that are used to control the flies just so we don’t have resistance,” he says.
Jim Humphrey, an MU Extension livestock specialist based in Andrew County, says fly tags are the go-to treatment.
“Fly tags are probably used as commonly as about anything,” he says.
Dewell says producers can alternate the basis of their fly tags, and should make sure the pour-on treatment has a different active ingredient from the tags.
“We don’t want resistant flies all through summer,” he says.
In addition to mixing things up to avoid fly resistance, Humphrey says safety is important. Producers should use gloves when handling fly tags and avoid touching their faces.
Hoffman says horn flies are usually the main antagonist, and late May and early June is when they start to become an issue. Horn flies can affect performance and rate of gain as cattle spend more time under trees or in water looking for relief.
“Animals aren’t going to graze as much and won’t grow as much,” he says.
Dewell says face flies can spread pink eye and other diseases, and horn flies can have a variety of impacts.
“They eat enough blood and cows don’t consume as much grass. It can lead to lower weaning weights,” he says.
Humphrey says calves can lose up to 20 pounds due to fly problems from the weight they would otherwise achieve.
“You take 20 pounds a calf, that can be a lot of money,” he says.
Humphrey says producers can feed insect growth regulators in mineral to help combat flies at the larva stage. Producers need to keep providing fly control throughout the year because they can reproduce and become a problem quickly.
“Some of these flies’ life cycle is pretty short, even 20 days or less,” Humphrey says. “We can be doing a good job on these flies, but if we stop and get a lot of rain, it can change.”
Provided producers don’t put them in too early, fly tags can work for most of the peak fly season, Hoffman says.
“Fly tags, that typically provides effective season-long relief,” he says.
Hoffman says the goal is to time putting in fly tags as close as possible to the start of the emergence of horn flies, usually around early June.
Dewell says putting in fly tags a little later, as opposed to in early May, helps make sure they are working for the peak time.
“Those fly tags only work for 60 to 90 days. If we put them on in early May, halfway through the summer they aren’t working as well,” he says. “If we can wait until (late May) or early June, then come in with a back scrubber later, maybe in the fall, that can work well.”
The back rub structure allows cattle to get treatment while scratching their backs, and they can be sized for full-size cows or calves. Spray-on treatments typically last for a shorter window, three to five weeks, but they can be applied quickly. They are also another option for the late summer or early fall months after fly tags are no longer as effective.
“Those are pretty good complements,” Dewell says.
Follow label directions on fly tags and pour-on treatments, as they can vary from cows to calves depending on size.
The goal is not to have no flies at all, but to control them.
“We’re probably not going to eliminate all of the flies,” he says. “We’re just trying to keep them at a manageable number.”