Horn flies are small pests that can eat a big hole in a cattle producer’s profits. Horn flies cause production losses by reducing gain, feed efficiency and milk production. High infestations have been shown to reduce stocker gain by 13%.
The threshold level to start fly control is when fly counts show 50 flies found per side of the beef animal. Economic threshold for flies (number of horn flies per animal at which the value of damage is equal to the cost of control) is 200 flies per cow.
Fly control can be achieved by self application devices, pour-ons, ear tags and spraying. There are a wide choice of insecticides, cost and effectiveness.
Back rubs and dust bags are self application devices. For this type of system to be effective forced use is best. Have bags, or rubs in situations where cattle are forced to use them. Example would be at a fenced off water or mineral source. Hang bags or rubs at chest height on the animal. Recharge regularly.
Fly tags (ear) can be effective against horn flies. Horn fly populations can develop resistance to most of the insecticides used in tags. To effectively use tags, it is recommended to rotate tag type yearly, based on the type of chemical in the tag. For example, in year one use a tag with either Endosulfur or Abamectin as the active ingredient, year two use a tag with an Organophosphate as the active ingredient. The third year use a tag containing a pyrethroid compound. If a tag provides less than four to five weeks of control, switch to another tag containing a different class of insecticide. We also recommend that other types of labeled insecticides be used such as sprays or pour- ons. Try to use an insecticide of a different class than the one used in a previous application.
Other tips for effective ear tag use are to use two tags per stocker or cow. Nursing calves do not need tags if cows are tagged. Do not tag cattle with fly tags until fly control is needed. It is also important to remove ear tags at the end of the fly control season. These steps will aid in preventing a fly resistance to insecticides.
Pour-on and spray-on insecticides assure each animal is treated. Several pour-on products also provide internal parasite control. Again, to prevent a resistance problem, properly rotate insecticides based on active ingredients.