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MU Extension Photo Fly Season is Here So Begin Fly Control Early

MT. VERNON, Mo. — Flies, especially horn flies, are starting to show up in significant numbers in some area beef herds according to Eldon Cole, a field specialist in livestock for University of Missouri Extension.

Research shows that horn flies can be on cattle up to 200 flies per animal and not create an economic loss. Over 200 horn flies though the loss of blood and being annoying results in poorer performance.

“The 200-fly threshold is hard to evaluate unless you are an entomologist,” said Cole.

Besides a loss in performance, blood sucking insects transmit diseases such as anaplasmosis. Flies are also a factor in pinkeye outbreaks.

Fly control is possible on most farms but the trick is to start early. Choose from a variety of practices such as oral larvacides, back rubs, dust bags, periodic sprays, pour-ons and insecticidal fly tags.

“If you are not comfortable using pesticides, walk-through fly traps may help. They require close observation and tend to control only 50 to 60 percent of the horn flies,” said Cole.

Resistance to some of the fly control materials exists so Cole says to monitor which products you have used in the last few years. Keep this information available when making product selections.

“Each method of control has limitations, so be persistent. If a method does not keep the threshold numbers below the target, search for another treatment,” said Cole.

Genetic differences in cattle attracting flies does exist so observe them closely, both those that attract flies and those that have few flies and consider it when making breeding stock selections.

For more information, contact any of the MU Extension livestock field specialists in southwest Missouri: Eldon Cole in Lawrence County, (417) 466-3102; Andy McCorkill in Dallas County at (417) 345-7551; Elizabeth Picking in Howell County at (417) 256-2391 or Dr. Patrick Davis in Cedar County at (417) 276-3313.