Get XP 820 fly tags, they are incredible. I used to spend several hours each week spraying by hand, putting up rubs, trying every chemical out there, then I tried these tags and the flies just disappeared! I just love them, the cows are totally relaxed and happy. And they don't affect the dung beetles as far as I can tell. And I still have parasitic wasps by the thousands even though I don't know what they are eating since there are so few flies. I put two tags on the back of the ears for cows, one for the older calves. Even if you miss a few, if the majority of your cows have them their tags will take care of the flies on the missed ones. I just can't believe how well they work. Used them last summer and this summer, they still work great, will rotate to whatever the company recommends next year, Warrior I think they said. Wish I had found these tags when they first came out a few years ago. Our flies are resistant to the two main types, this is something different. These tags absolutely changed my life. Oh also they require a Y Tex tagger. Also, they appear dry and have no odor. Also for some reason I had just one get infected and have to be cut out, usually I have five or six with other tags. So that's a plus too.