Controlling fly problems during the summer months can be a challenge, but effective control methods also can bring a 15 to 25 pound gain. While insecticidal ear tags work well against horn flies, highly pyrethroid-resistant horn flies dominate many areas of the country. Horn fly resistance to pyrethroids increases or subsides locally according to recency and duration of pyrethroid use. Therefore, organophosphate (OP) ear tags or an alternative control method should be the basis of horn fly suppression. If you are using fly tags, experts recommend that you use OP tags for two years then switch to pyrethroid tags for one year, then rotate back to the OP tags for another two years.

If you're placing cattle on pasture and don't know the history of pesticide use on them, your best bet is to start by using OP tags the first year.

And as the end of summer rolls around it's suggested that you initiate alternative control methods. During August and September additional fly control (dusts, backrubbers, occasional sprays or pour-ons) may be needed to control late fly hatches as fly tags begin to lose effectiveness.