I’ll put in a plug for this here:
I’ve braided cattle ear tags into the mane and tail and have been really quite impressed. Tails are quiet when grazing, which I’m not sure I’ve EVER seen before. I’m pretty well sold on this as another tool in the box on the war on flies.
I’m using this one:
https://www.valleyvet.com/ct_detail.html?pgguid=36F745B1-C9B2-4DCA-B9C0-632165232D7A&q=trizap
There are other options, too. I (personally) wouldn’t consider using any of the organophosphate tags but this one and plenty others are pyrethroid based.
Guessing that if you bathe frequently it won’t work as well, but it seems to do okay with occasional hosing. My horses have been wearing them for a couple weeks now? They’re supposed to last months!