This is a fascinating thread and I hope it will run for a while longer.  There
is an obvious conflict between those who get their living directly from bees
and have their family to feed and workers and bills to pay NOW and we amateurs
who have the luxury of a long term view.
  The professionals can do their sums and add the cost of labour to the cost
of chemical treatments and keep their fingers crossed with regard to residue
build up, resistance to the chemicals they are using and the reputation of
honey as a wholesome product.  The majority of such contributors to the list
opt for the chemical option and who can blame them.
However, I am sure that they nearly all would agree that selection of the bees
for resistance to disease ( and it is mainly Varroa and its associated
problems that I have in mind) is the best option long term.  The problem is
that the more efficient the chemical treatment the less "incentive" for the
bees to select a resistant strain and the greater incentive for the mite to do
so.  The efficacy of chemicals can probably be prolonged by alternating
between different chemical treatments that are available (in some countries
only) but there is still no selective pressure on the bees.
It seems to me that if we all adopt the least efficient method that we,
depending on our circumstances, and enough of our bees can live with, the
sooner varroa tolerant strains of bees will emerge.
At the same time, of course, the Varroa mite will also be suffering from
selection pressure.  At the moment it is an inefficient parasite in that it
kills its host.  If enough inefficient beekeepers manage to stay in the game
for long enough the mite should evolve to be a more efficient parasite that
nobody notices.
Bees must have been challenged with varroa in Stefan's country for most of his
39 years.  Romanians have not yet achieved a world wide reputation for being
efficient beekeepers.  It would be interesting to learn Stefan's methods of
varroa control and those of his local colleagues and whether any signs of
resistance of bees to varroa mites is emerging.
Chris Slade