Lesgold,
When I first researched about keeping bees, and before getting any bees at all, I made a decision based on my philosophical mindset.
I would be treatment free. If I was going to have to add medication/poison to keep them alive, then I wouldn't keep bees at all. I haven't for a moment believed that all the feral bees died out from varroa. They have been there all along, coping through nature. I reasoned that if they could live in the wild without treatment, then I should be able to keep them that way also. I like neither the idea, the cost, nor the trouble of treatment. This probably stems from working in the chemical section of a retail nursery when I was younger.
So, how have I kept them alive without treatment? Beats me. But, here are some things I have always done.
1. I keep my bees in long hives, but I doubt that makes any difference. I dismiss any idea that long hives are in some way a more "natural" beekeeping method.
2. I use foundationless frames. I have from the start. That means the bees build whatever size cell they want (ie. small cell). I don't restrict drone cell either.
3. I don't buy bees. I never have. I got started beekeeping by catching a few swarms. That means most of my bees are the little grey feral bees. However sometimes a swarm may be larger and yellow, which I suspect comes from some other beekeeper's yard. I consider the little grey bees to be feral, more hardy, and more resistant to varroa as well.
4. I always pull spring nucs, sometimes taking the old queen, but sometimes not. I do this to keep my bees from swarming, and I sell off the extra so I can strictly keep my own apiary down to 3 or 4 hives and a couple of nucs. (I live in close quarters suburbia)
5. I don't feed bees in general. Why should I? I leave them enough of their own honey, which is better for them anyway. No sugar water or pollen patties. Now if I catch some late season swarm, then I might feed that nuc a little.
It is true that I have lost a couple of colonies, but those were from sheer stupidity. I have weakened hives by pulling too many nucs, and they couldn't stave off hive beetles, or some such error on my part. Every loss so far I can trace back to some obvious fatal mismanagement. In 6 years I have had no winter losses, although I am sure my hives have varroa also. I imagine that every colony in America does.
All these factors above may be reasons for treatment free success, such as a minor beek like me enjoys, but I have no proof.