Hi All,

We currently hear of the increase in the rate of winter losses.
vanEngelsdorp* writes that "Prior to the introduction of varroa mites into
the U.S., beekeepers reported 5–10% winter losses. These losses rose to
15–25% with the introduction of varroa and tracheal mites in the mid-1980s
[4]<http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004071#pone.0004071-National1>.
Here we report a second year of greater than 30% colony loss....Those
beekeepers with multigenerational knowledge and experience can comment with
authority on what “normal” losses are. Respondents to this survey were less
likely to think their losses were “not normal” when compared to last year's
survey [14]<http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004071#pone.0004071-vanEngelsdorp1>.
During this survey, respondents reporting normal losses lost an average of
21.7% as compared to an average “normal” loss of 15.9% as reported
previously."

What I'm curious about is the validity of that "normal" 5-10% winter loss
rate.  Is that a realistic figure, or rather the "acceptable" rate that
happened in good years?

In the Beeinformed 2011-2012 survey (a warm winter), the 95% confidence
interval for mean percent losses by commercial operations lay between 15
and 30%.  Since a large proportion of those operations go to almonds, and
would be expected to combine weak hives to make grade, I'm wondering just
how much higher the winter loss rate is these days in operations that
manage varroa well?  (It would expected to be higher for those who don't
manage varroa).

Does anyone have any actual data or experience as to what realistic (not
best case) winter colony losses for U.S. operations used to be for the
majority of colonies, which are run by large commercial operations?



*http://www.plosone.org/article/info:doi/10.1371/journal.pone.0004071

-- 
Randy Oliver
Grass Valley, CA
www.ScientificBeekeeping.com

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