I find this discussion on nosema to be of great interest.

During the CCD epidemic from 2003-2009, most of what I've seen strongly
implicate *N. ceranae* as a major factor--especially since it is one of the
few pathogens that is well documented to cause the field signs of sudden
colony depopulation (and which I've confirmed a number of times).

And as Jerry points out, *N ceranae* and some viruses can be a deadly
combination.

That said, I live in a relatively short-winter area, with only a month of
brood break at max.  I decided not to go the fumagillin route, and to breed
only off of strong colonies each spring.  After several years, I can
generally find some nosema spores in gut samples in my colonies, but no
where near to how prevalent or numerically high as they were during the CCD
epidemic.

And when I've tracked nosema counts and prevalence over winter, there was
no correlation with colony performance.

I do not doubt in the least that nosema can be a serious problem in
long-winter areas such as in Canada.
I do see that colonies in spring on a good pollen flow can have sky-high
nosema counts, yet thrive.
I don't know why I hear of midsummer nosema epidemics in the Midwest.

As far as I can tell, there are still many unanswered questions as far as
the impact of *N. ceranae* on colony health and survivorship.

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

             ***********************************************
The BEE-L mailing list is powered by L-Soft's renowned
LISTSERV(R) list management software.  For more information, go to:
http://www.lsoft.com/LISTSERV-powered.html