Bill said:
> So the X could be any stress factor like mites, drought, etc., but the 
> underlying requirement is Nosema.

An attractive aspect of this hypothesis is that it could possibly explain 
the historical collapses prior to mites, especially if one takes into 
account that viral transmission in bees and other insects is closely 
associated with nosema infection.  This hypothesis requires nothing but poor 
weather prior, and a reservoir of nosema and viruses (which bees have 
apparently always had at low levels).  It would also handily accept periodic 
viral mutations that could cause temporary epidemics.

Nosema infection creates a positive feedback loop.  Poor nutrition makes 
bees more susceptible to nosema.  Nosema then impairs digestive function, 
hampering nutritional uptake.  Nutritionally-stress bees are then even more 
susceptible to nosema...

At some point, viruses might then reach critical levels to kick off an 
epidemic (see my article on mite population dynamics).

The combination of bees then dying at an early age, due to nosema and virus 
infections, would lead to rapid collapse of the adult bee population.

The presence of mites, pesticides, and other stressors would serve to 
exacerbate the potential for collapse.

Let me make it clear that this is a hypothesis to be tested.  I am not in 
any way claiming that this explanation has merit until tested.

Perhaps we could hear from any lurking researchers how the data fit this 
hypothesis.

Randy Oliver 

******************************************************
* Full guidelines for BEE-L posting are at:          *
* http://www.honeybeeworld.com/bee-l/guidelines.htm  *
******************************************************