Chris Slade:  Colonies should be surveyed for mites in the spring to see
what level of Varroa is to be found.  Depending on where you are located
(northern climes) you should be able to treat with Apistan once in the fall
about mid August.  Take the honey off early and let the bees store Sept.
honey in the brood nest for winter.  I've never heard of a fall flow heavy
enough to fill one or more supers, so I usually suggest that the bees be
required to put the fall flow in the second brood nest for winter.  That
way treatment can be done before mite levels cause collapse.  From my many
observations, it appears that fall collapse occurrs when the hive space is
reduced AND when fall temperatures are experienced.  Removing supers in mid
to late August does not appear to initiate colony collapse.  In fact,
colonies in apiaries where one or more colonies are found with 1500 mites
on a sticky board appear to respond well to the treatment, perhaps only
losing ten percent of their old bee population.
 
In the first year of an infestation (of HBTM or Varroa), or the year
following a proper  treatment, colony collapse appears to be limited to the
old bees.  Observations suggest that these young bees go into the winter
well as a smaller than normal cluster.  In the second year of infestations
without treatment, total colony collapse occurs.  By proper treatment of
Varroa I mean the use of one Apistan strip per each five, or less, deep
combs of bees (or equivelent in smaller size combs), for the recommended
time period stated on the label, or a 30 day treatment in the spring and
another 30 day treatment in the fall.
 
I am not aware of any research which proves that viruses kill colonies.
Viruses have been found in dead colonies and there is some evidence that
viruses may be associated with the presense of Varroa.  And there is data
that shows that viruses exist in U.S. bees.  It does not follow that
viruses kill colonies.  To my knowledge "crawlers" do not constitute an
"obvious sign of virus(es)."
 
James C. Bach
WSDA State Apiarist
Yakima WA
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