John Valentine speculated that Ed Lord may be able to offer some
information regarding "open bottom" double hardware cloth bottom boards
as a possible Anti-Varroa Floor.
 
Ed Lord is a member of my beekeeping association (the Southern
Adirondack Beekeepers Association), so I gave him a phone call to ask
his advice on his use of open bottom boards, and permission to pass on
our conversation to the list.  He was happy to give both.
 
Ed uses 1/8 inch hardware cloth to build double screen bottom boards for
his hives which he keeps atop pallets.  Initially he built these boards
to improve ventillation for his bees when he was moving them to Maine
for blueberry pollination.  So pleased was he with the results that he
started using these open bottom boards year round.  He feels that the
improved ventillation helps his bees through the winter, as there is no
condensation and subsequent moist/wet bottom boards.  Remember that his
open bottoms sit on top of pallets so even though the bottom board is
hardware cloth, there is still some wood to provide a modicum of winter
protection.  Ed attributes the loss of only one hive to his screened
bottoms and that was due to a wind tunnel effect that resulted from
a combination of unfortunate placement and an open upper entrance.  Upon
inspection he discovered that the hive was full of snow.
 
However, when I asked Ed if he noticed any positive effect on varroa
populations which he could attribute to his open bottom boards he was
real clear that he could NOT claim any positive effect.  He related his
varroa experiences which were typical for these parts (serious, almost
devastating problems in '95, nothing in '96 and '97, minor problems in
'98).  "These parts" are middle upstate New York approximately following
the Thruway/Northway corridor from about Ravina/Selkirk to Saratoga -
not considered western NY (apologies to those not intimately familiar
with the geography of NY).
 
The long and the short of it from Ed was, open bottom boards are GREAT
for ventillation but he noticed no improvement regarding varroa.
 
Aaron Morris - thinking no silver bullet here!