Boston Bees
Bumblebee
I’ve no idea what number of mites to expect to see on the board...above what number would be considered indication of a varroa problem?
It's a very difficult question, as it depends on how many bees there are left in the hive, whether there is currently brood, etc. If you are down to your last few hundred bees, there won't be many varroa either.
But see how you go