>Would the sample rates be higher
because most if not all of the adult mites are on adult bees?

Yes. But the mites are there and were there before the break. Only made visible by the absence of brood. I am in a much different climate (eastern WA) but have often seen the same condition. There is also the possibility of the often noted fall invasion but this doesn't really sound like it. Observed DWV would indicate a long standing mite load. A good understanding of mite population dynamics is helpful. Randy's page has an excellent predictive program available. The key is to understand that the mite population must be kept low through out the season. Not easy with a long honey season but possible with new tools. 

Paul   

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