Re: Validity of Mite Drop Test
Mites, like everything else, get old and die. The other ones that end up on the drop board are immatures that didn't get old enough to live by the time the bee larva emerged.
Drop board data is open to interpretation, for example with seasonal influences (brood, no brood). But as a general rough guide they can be useful, every starting out beekeeper should use a drop board at least at first, just so they are aware of what is going on, and mite population changes etc.
If a hive has no hygienic, or other, mite control mechanisms, that may mean less mites may show on the board. But then the mite population would grow unchecked, so in time, more mites would show on the board.
Other thing with drop boards, mites can be on them, next day you look, they are gone. Could be ants, whatever. So a zero read is not necessarily zero.
44 years, been commercial, outfits up to 4000 hives, now 120 hives and 200 nucs as a hobby, selling bees. T (mostly).