This has been presented earlier as a hypothesis.  Could these metabolites in colonies actually kill or affect the behavior of much smaller mites vulnerable at much smaller doses that bees or varroa?  The dramatic disappearance of tracheal mites from the US starting in the early 2000s coincides in time with the widespread use of Amitraz.  The alternative explanation, that their disappearance came through widespread genetic resistance is not as compelling.  Why would genetic resistance not have appeared earlier if it were possible, given that tracheal mites arrived two decades before the dramatic drop in their numbers.  And if genetic resistance to tracheal mites appeared with not much effort in active breeding, why has a parallel situation not occurred regarding genetic resistance to varroa?

Around the early 2000s I heard a presentation by the director of a large US honey cooperative at a national meeting.  He tangentially talked about how their chemist tracked a number of compounds and disclosed that the chemist was finding batches of honey with extraordinary levels of Amitraz (or perhaps a metabolite- do not recall).  In seeking an explanation they traced these hot batches to extractions of honey from older brood comb.  I asked him later whether those numbers could be seen if kept confidential.  He said I would have to talk to their chemist.  There were a few communications with the chemist, followed by silence.  As was pointed out, there are numbers and reports and conversations out there, but very difficult to retrieve.  The phrase "I do not recall" seems to fit here.

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