The flys are out in full force so its time to start protecting our herds.
Insecticide ear tags are still very useful fly control tools. Rotating between organophosphate and pyrethroid products is recommended. The suggested rotation schedule is to use organophosphate tags for two consecutive years, rotate to a pyrethroid tag for one year, then back to organophosphate tags. Chemical rotation is a good idea with any method of fly control. Keep in mind that flies are a vector for pinkeye.
Rotation between chemical classes is necessary. That is more than changing brand names. Check the active ingredient of the products you are considering and determine its chemical class. Some classes of insecticides are more prone to developing resistance than others. Flies will develop resistance to pyrethroid insecticides very easily and quickly. Organophosphate insecticides have documented cases of resistance, but aren’t as prone to resistance as pyrethroids. Macrocyclic lactone and insect growth regulators have very few or no documented cases of fly resistance. Be sure to consider these characteristics when developing your resistance management strategy.
We have a long fly season in the South. Season-long horn fly control will likely require two or more methods, applying two or more products from different chemical classes. Keep insecticide resistance management in your fly control plans.