Treated wood for any hive components that come into contact with the bees is
BAD news.  The most common preservative is CCA, chromated copper arsenate.
If this salt works its way to the surface, which it can and does, it could
potentially contaminate all the honey, wax, etc.  I am unsure of its effects
on the bees, but its effects on humans, while insidious, can be devastating.
 
Other preservatives, such as pentachlorophenol and copper naphthenate, are
primarily fungicides.  They can reduce hive populations significantly if not
used under very controlled conditions.
 
Bottom line - Preservatives aren't very practical for beekeeping, unless its
the wood keeping your bottom board off the ground.  A good coat of paint, or
better yet a soaking of a mineral spirits, exterior varnish, paraffin solution
 followed by a coat or two of quality paint will make those bottom boards last
for many years (with reasonable care, of course).
 
Good luck in your quest for the everlasting bottom board.  Please let me know
if you find the secret.
 
Ron Bell
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