"Efficacy of a bottom screen device, ApistanJ , and ApilifeVARJ in
controlling Varroa destructor . Ellis, James D., Jr., Keith S. Delaplane, &
W.Michael Hood. 2001. American Bee Journal 141(11): 813-816

ABSTRACT This study tested the efficacy of a hive bottom screen device in
controlling varroa mites, when used alone or in conjunction with the
miticides ApistanJ and ApilifeVARJ. Thirty six colonies were equalized and
each assigned to one of six treatments: (1) no treatment, (2) bottom screen,
(3) Apistan, (4) Apistan + screen, (5) Apilife, and (6) Apilife + screen.
Adult bee populations were not affected by treatment, but the number of
brood cells was significantly reduced in colonies treated exclusively with
Apilife compared to that of colonies treated with Apistan or exclusively
with a bottom screen. Brood production was numerically highest in colonies
treated exclusively with a bottom screen. Varroa populations were
significantly reduced in colonies receiving acaricide compared to
non-treated colonies. Varroa populations in colonies treated exclusively
with a bottom screen were 14.9 % lower than that of non-treated colonies,
but this difference was not significant. The bottom screen did not affect
the percentage of varroa mite population phoretic on adult bees. Apistan
provided 100% mite control in South Carolina whereas in Georgia it provided
0% control in colonies treated exclusively with Apistan. With the addition
of a bottom screen, Apistan-treated colonies in Georgia experienced an
average mite control of 44.3%. This suggests that fluvalinate resistance
exists in Georgia varroa mites. It also indicates that a bottom screen may
help compensate for reduced acaricide efficacy. Average efficacy of Apilife
ranged from 65.2 - 97.1%. "

http://www.ent.uga.edu/bees/Research/archives.htm

I'm sure Cornell can get a copy of the full research (and suprised you don't
already subscribe to the publication of such in your own field, since there
are so few doing research).

-----Original Message-----
From: Peter Borst

I have been working at Cornell for three years now ... The research
community does not support the idea that screened bottoms do anything alone;
a few people say that when used in connection with fumigants or apicides,
they may enhance the effect of these substances. I have asked this group
repeatedly to show studies proving their effectiveness.