> Keep your hives in good shape and good low counts and immigration  should be a tiny issue.

You are choosing to dismiss the evidence and opinions of a large number of qualified beekeepers and bee researchers. Dr Spivak has been talking about this problem publicly for over a year, Dr Seeley has shown how isolated hives have much lower mite buildup than hives in apiaries, the list goes on. 

What I have seen in my area is that mite levels are usually flat during the season and then the spike in August. I can't prove they come from other hives, but that is how it appears. It doesn't really matter that much, the point is that bees in this area have to be treated in August before the late honey flow. 

Prior to the MAQs, there was no legal way of doing it with the supers still on. A lot of beekeepers started doing "flash formic" treatments about ten years ago, and learned that quick vaporization was effective and tolerated by the colonies. I prefer the strips because I don't like handling bulk formic acid, having done so at the research lab. 

PLB

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