I used screened bottom boards for the first time this year and they seem
quite successful. My hives are strong and the mites don't seem to be a
problem. But I'm wondering about over wintering with the screened bottom
boards.

I could leave them on or replace with regular bottom boards. For winter
insulation, I use large packing-style crates that cover each pair of hives
shoved in close together I then use straw as an insulator all around and on
top of the hives leaving, of course, a vent at the top. The hives and the
crate sit on a 2x6 stand. The bottoms are not closed off.

Winters in Southern Ontario can be long and cold and may go below -20 C.
There might be enough snow to cover the bottoms of the crates to keep the
wind out but, then again, there not be.

Does anyone have any experience, bad or good, with leaving screened bottom
boards on all winter?

Jay Mowat
Erin, Ontario