Not a few centuries. Less than 3 generations is sufficient - they don't
have to adapt new ways to deal with the mite, but regress to the point
that their current methods are effective again. We have resistance here
in our small cell hives, not by genetics but by allowing the bees to be
natural and by following natural selection and not coddling our hives. I
suspect you do have feral colonies there, even if not abundant - look
for them. Those are the bees you want. They are the survivors. Bees and
mites have co-existed for millions of years - nothing has changed now
except for man and his tampering. Nevertheless, continue hunting -
nature always finds a way and your solution is out there already. The
industry wants you to think it's impossible because to them, impossible
means money. In reality, it's trivial.