Controlling flies can both add value and improve performance of cattle. Face flies and horn flies are an annual problem on beef cattle. The fly season starts in April and runs through September.
Flies reproduce rather rapidly, which makes them more difficult to control. Horn flies have a generation about every two weeks and face flies every eight to 10 days.
Horn flies are blood suckers that irritate cattle and interfere with feeding and resting. Face flies also annoy cattle, interfere with feeding, cause excessive eye secretions, and transmit pink eye, which results in reduced weight gain and milk production. USDA research reported that heavy infestation of flies resulted in cows losing about one-half pound of weight daily and a 20 percent reduction in milk production. The Tennessee beef industry annually loses millions of dollars due to these two pests.
"On-the-farm" demonstrations conducted in Tennessee in 2001 showed that backgrounded calves "tagged" with insecticide treated ear tags gained 2.34 pounds per day compared to 1.6 pounds in the control group (non-tagged). Over a 120-day period, this would produce an extra 88 pounds per animal. In cow-calf herds, calves from herds treated with various insecticide treated ear tags gained 2.84 pounds per day compared with 1.90 pounds per day for calves with no fly control. Over a 120-day period, this would total more than 100 pounds extra weight to market. The level of response to fly control will also be influenced by the level of infestation.
Considering the added weight gain due to fly control and the reduced value of feeder cattle that results from pinkeye infection, producers can easily see the economic advantages to controlling flies.
Plan fly control strategy early. Methods of control include spot-ons, pour-ons, dusts, dips, sprays, backrubbers, oral larvacides, boluses and ear tags. Consider what was done the past year or two when making plans for this year. Insecticide impregnated ear tags have been one of the most popular methods of controlling flies since they became available. There are three main groups of ear tags: those that are impregnated with an organophosphate, those with a synthetic pyrethroid and those with both. Use a tag which has either a phosphate or a pyrethroid but not both. Flies tend to become resistant to an insecticide that is used for several consecutive years. Therefore, alternating between the phosphates and pyrethroids each year is recommended.
Since most ear tags are effective for only about five months, researchers also recommend waiting until the first of May to place them on the ears of cattle. This is later than would normally be recommended for more conventional methods of fly control.
Due to the mild winter, flies may become a problem earlier than normal this season. You may need to use several sprays or a backrubber until ear tags are in place.
A combination of practices may be needed periodically during the fly season. If tags are used and flies begin to build up in the peak fly season, supplemental treatments such as a spray or pour-on may be necessary to bring them under control.
In summary, evaluate last year's fly control program. If an ear tag was used, rotate to a tag with a chemical of a different family. Keep close watch on the fly population and use a supplemental control measure if necessary. Have a plan in mind.