> Nosema ceranae doesn't "cause" winter mortality.
> no significant differences in N. ceranae incidence
I have a number of issues with the cited study.
Mainly, "incidence" means nearly nothing, since at no point was "incidence"
less than around 75% of colonies.  And if they'd taken larger bee samples,
they would likely have hit 100% "incidence" in all colonies at all times of
the year.
I've published comparisons of spore count data vs. prevalence data (percent
of bees in a hive infected).  The latter is far more informative, going
back to early work by White, then by Higes, then Matt Smart, as well as by
me.
And if there's pollen coming in, nosema flourishes, but may not cause
issues.
The authors also speak of "signs of nosemosis" without any supportive study
that ever showed that nosema causes dysentery.
The above said, my own data for hives in California are in agreement with
that of other authors who have studied prevalence -- as the percentage of
bees in a hive increases above about 30%, colonies build up more slowly and
produce less honey.  At above 70% they may suddenly collapse with the
mentioned "signs of CCD."

Randy Oliver
Grass Valley, CA
530 277 4450
ScientificBeekeeping.com


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