Hi Stan and all,
 
Sorry not to answer sooner.  On purpose I do not have a computer at
home.  After doin' it all day I leave it at the office.
 
Regarding varroa: their preferred host is drone brood.  This is due to
the drones' longer development time which favors more mites reaching
maturity while the drone cells are capped.  Early in the season when
mite populations are low and drone populations are building, the mites
will target the drone cells.  My understanding is that mites don't
target worker brood until the drone population is decreasing (late
summer/fall) and the mite population has risen to the point that there
aren't enough drone cells to go around - then they migrate to worker
brood.  If the varroa population reaches that point in their dynamics
it's a pretty sure bet the hive will collapse soon afterwards, unless
the beekeeper steps in, and even then it may be too late.
 
When drone trapping, if you start early and keep trapping, you keep
your drone population coming (the method calls for encouraging
construction of drone cells) and you keep the mite population in check
by removing them from the hive before they get the chance to emerge from
the drone cells.  By the time the queens stop producing drones, the few
mites that are still present in spite of drone trapping will not be of
numbers sufficient to crash your hive in the time remaining in the
season.  You can harvest your fall crop and the get in a fall treatment
of Apistan to knock out the rest of the varroa population.  Drone
trapping is not touted as the final solution for varroa control, rather
it's another tool in IPM (integrated pest management).
 
Now for the record, I do not trap drones (although in retrospect I will
certainly start next year!).  In my parts we get two major flows, early June
to mid-July and late Aug to mid-Oct.  A mid season Apistan treatment
means kissing off the fall flow.  I have relied on Apistan twice yearly,
which worked well in '96 and '97, but I expect that this year I should
have forsaken the fall flow (which was very good) and treated in
September.  I am seeing ominous signs that I waited too long.  What
worked well in previous years may spell disaster in '98.
 
Drone trapping seems the only alternative right now, until (if?) gel-formic
is released.  Apistan timing just doesn't coincide with the flows in these
parts.  Bob Horr's article claims that drone trapping will keep varroa
populations in check throughout the season (provided you start early
and keep it up all season) such that you can get by with a single post-
fall-flow Apistan treatment in the northeast US.  The bad news is it's labor
intensive and the constant drone cell building cuts down on honey yield.
 
Having said all this, I'll capitulate.  I guess drone trapping could
select for mites that prefer worker brood.  I do not know for sure that
ALL mites will target drone brood if the drones are available.  It COULD
BE that there is a population of mites out there who prefer worker brood
and it COULD BE that drone trapping will select for that portion of the
varroa population.  Current research has not detected that population
(which does not mean it does does not exist) and if every beekeeper
starts trapping drones, then that heretofore undetected portion of the
varroa population could come to the forefront.  All the more reason to use
drone trapping as part of an IPM strategy rather than the sole weapon.
 
Aaron Morris - thinking too many problems, too few solutions!