It is difficult to estimate how many dollars a year flies cost the cattle industry per cow or yearling but it's substantial.
"It's worth spending money to control horn and face flies because fly numbers are building at this time. The dollar returns should be greater this year because of the favorable cattle prices," said Eldon Cole, a livestock specialist with University of Missouri Extension.
Prevention of fly buildup on pastured cattle may involve feed-through products that interrupt the development of some flies in manure piles. Spraying periodically, insecticidal ear tags, dust bags and backrubbers may be used by some farmers. Others may incorporate more than one of these practices during the summer.
"Each of the practices has advantages and disadvantages. Some work one year but not the next so fly control requires study, record keeping and comparison. Cattle owners must realize they cannot eliminate all flies from their herd," said Cole.
Horn flies and face flies seem to be the most troublesome of the winged pests according to Cole.
The horn fly is a blood sucker and causes discomfort while cattlemen fear the face fly because of its ability to spread pinkeye. Anaplasmosis is another disease that can be transmitted by blood feeding flies.
Cole says a well-placed back rubber may be one of the most economical ways of controlling horn flies. The rub must be where cattle frequent it every day or two.
"If the cattle avoid it or you fail to keep it charged with a pesticide it won't work. Farmers who are on a rapid, rotational grazing system may need to use a portable back rub. Locating a rub near shade, water and mineral feeding areas is desired," said Cole.
The insecticidal fly tag is still useful unless fly resistance has built up among the local fly populations. Cole suggests tracking from year-to-year the tag used and its effectiveness.
The two insecticidal products used most frequently are organophosphates and pyrethroids. Follow label instructions regarding tag choice, placement in ear, number of tags per head, safety precautions and class of animal. Some may be used on lactating dairy cows but not all. Calves over three months of age may be tagged.
"Avoid selecting an insecticidal tag just because you like the color, or you have a tag applicator that the tag works with," said Cole. "Visit with your veterinarian, farm supply manager or extension livestock specialist about fly control possibilities for your herd."
Source: University of Missouri Extension