If you  do a sugar drop,  then you are familiar with the live varroa mites and how easy to spot they are because they struggle so in the powdered sugar.  It leaves little "funnels"  super easy to spot.   Screened bottom boards and sticky boards are pushed with the premise mites fall down.
I did some experiments last fall,  and the accuracy of the boards count was questionable at best.    Many here like to do math and extrapolate the final numbers.  Unfortunately I have a quality control background,  and can assure you the math would not pass muster.  Gage error is way over acceptable with sticky boards.  It’s a little better with sugar drop,  but IMO still unacceptable.

In my experience Healthy mites don't fall much, if at all.  The board collects mostly dead ones.  Given that a large number leave the hive on bees, or are drug out with the trash, trying to use sticky boards to get good numbers is difficult at best.

The other factor mentioned,  "not opening the hive in winter" is a problem.  You need to know and decide to manage, long before winter.  Mite levels should be known (if you care to) at least one brood cycle before the first frost.  A bit earlier would be better so that you can make decision, and manage and still get healthy winter bees.

Charles

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