Hello Aaron and All,
 Cornell's study says open or closed bottom boards make no never mind in all areas they examined.
Aaron Morris - thinking back to the drawing board.
Thanks for the update Aaron.  I am always amazed at many of these studies.  One reason why I like to do my own testing.   I am curious why U.S. testing of open mesh floors shows almost no help with varroa when in Europe the OMF gets high marks.    Although the OMF was never intended to be the total answer for varroa as Dr. Shiminuki said it is a tool for Ipm management similar to  drone brood removal.     We do know beyond a doubt varroa fall off bees. We know certain bees groom off varroa and drop those varroa mites. We  also know varroa WILL reattach to another bee UNLESS the varroa falls through a screen and is about a inch away from the incoming bees. Although I do not own a OMF I  still have a hard time discounting OMF all together. With Coumaphos resistant varroa found in Maine and Florida and the next chemical with at best a upper 50% control we may need every tool we can find to survive varroa. Although I am on the SMR bandwagon I still do not see SMR bees as the total answer. To put things bluntly I do not see breeding alone as the answer. I could be wrong and we will not know for sure about SMR queens for a couple years. Dr. Shiminuki a researcher  I always held in high regard although we had our disagreements always said "there may not be one solution to varroa but rather a combination of methods." I agree  with "Shim" but hope a simple solution to the varroa worldwide problem is found.
So far Dr. Carlderone, Dr. Caron (OMF 10% control at the lecture I attended two months ago) and Dr. Delaplane have all given the OMF low marks in the U.S..  In Europe the researchers seem to rate the OMF as an IPM tool much higher.    Why?
I have not tested OMF yet. Maybe I should.
Sincerely,
Bob Harrison