I say, let the mites be mites... Kirk says it very well (emphasis is mine):
"And now I have another terrible confession to make. Not one as bad and un-American as passing up short-term gain and investing in the future—but still horrible: I have never yet counted even a single sample of mites from any of my bees. I consider counting mites as a way of evaluating Varroa resistance to be fraught with all sorts of shortcomings and difficulties. It's very time consuming and hence the size of the apiary, the number of colonies tested, the gene pool, and the income available all start to shrink. It's also very easy for the results to be skewed by mites migrating from other colonies or bee yards. And it doesn't show which colonies are more resistant to secondary infections--a trait I consider very important."--Kirk Webster, ABJ April 2005, pg 314
"We're trying to ensure the failure of modern beekeeping by focusing too much on single traits; by ignoring the elements of Wildness; and by constantly treating the bees. The biggest mistake of all is to continue viewing mites and other "pests" as enemies that must be destroyed, instead of allies and teachers that are trying to show us a path to a better future. The more virulent a parasite is, the more powerful a tool it can be for improving stocks and practice in the future. All the boring and soul-destroying work of counting mites on sticky boards, killing brood with liquid nitrogen, watching bees groom each other, and measuring brood hormone levels---all done in thousands of replications---will someday be seen as a colossal waste of time when we finally learn to let the Varroa mites do these things for us. My own methods of propagating, selecting and breeding bees, worked out through many years of trial and error, are really just an attempt to establish and utilize Horizontal breeding with honeybees---to create a productive system that preserves and enhances the elements of Wildness. My results are not perfect, but they have enabled me to continue making a living from bees without much stress, and have a positive outlook for the future. I have no doubt that many other beekeepers could easily achieve these same results, and then surpass them."--Kirk Webster, What's missing from the current discussion and work related to bees that's preventing us from making good progress.
"I’ve thought a lot about how in the world to describe what’s really happening in an apiary that hasn’t used treatments of any kind for more than five years; where mites are now considered to be indispensable allies and friends, and where the productivity, resilience, profitability and enjoyment of the apiary are just as good as at any time in the past. I wouldn’t dream of killing any mites now, even if I had an easy and safe way of doing so."--Kirk Webster, A New Paradigm for American Beekeeping
"...when 150 queens were introduced into nucs with brood untreated for 18 months. This brood had a normal outward appearance when the nucs were made up, but four weeks later about half of them were starting to decline with PMS-type symptoms. But after another three weeks, almost all of these colonies appeared normal and healthy again."—Kirk Webster