Juanse said:  I am sure we can develop
> bees more resistant to nosema but for this, as with varroa, we need to 
> stop
> treatments for a while (accepting loosing some or lots of colonies) for
> selecting the resistant stock for further multiplication.

Hi Juanse.  I was thinking of you today--enjoying the beginning of summer as 
the weather turns cold in my hemisphere!

This is a common misconception--that it is necessary to let colonies die in 
order to develop resistance to a pest.
In my own operation, I try not to let any colonies die.  I do kill a lot of 
queens though, since what I want to die out is poor genes, not the bees 
themselves, since they die on an individual basis soon enough.

The point is, you can screen for resistance by letting nonresistant colonies 
die, OR you can screen for resistance by another method (e.g., stickyboards, 
microscopy), then breed only from those showing resistance.  Keep the best 
bees isolated as best you can in breeding areas, and run the rest for 
production (with appropriate treatments) to make a living.  Each spring, 
replace all nonresistant queens with resistant queens.

A beekeeper who is not making a living cannot well further stock 
improvement!  As Bob Harrison has pointed out, you need to breed from good 
producers to stay in business.  Breed for any other trait secondarily 
(unless you are a researcher, who enjoys the luxury of getting paid while 
accepting such losses in the search of promising genes, as John Harbo did 
for SMR).

Randy 

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