But ear tag application is much easier with cattle that already have an ear hole from previous ear tag use. On the other hand, in general, ear tags also are the most expensive treatment. The advantage of insecticide ear tags is that they can provide three to four months of highly effective fly control, and this reduces the overall cost of labor and insecticide. But Baldwin says the advantages of an ear tag quickly disappear if the fly population is resistant to the ear tag being used. Although resistance can develop with any means of insecticide delivery, ear tags are the most notorious because they provide constant insecticide exposure for most of the horn fly season.
Ear tags contain insecticides from two major chemical classes - pyrethroids and organophosphates.
Producers who experienced control failures with ear tags last year should not use the same ear tag or any other tag in that same chemical class for at least two years, Baldwin advises, saying research has shown that it takes about two years for a horn fly population to breed out resistance or to revert back to a susceptible population that can be controlled again with the same ear tag. Pyrethroid ear tags should only be used once every three years. Organophosphate ear tags can be used the other two years, but it is preferred that ear tags not be used at all in one of the three years, according to Baldwin. Recommended organophosphate ear tags include Patriot, Cutter1, Commando, Warrior, Cutter Blue, Terminator, Optimizer and Rotator. For additional information about horn fly control, contact an Extension agent in your parish LSU AgCenter office.