I am trying to show that Ernesto and all have singled out varroa as the most serious factor. There are other factors, but this is at the top of their list. Many of the beekeepers either thought they had varroa under adequate control, or they weren't really checking all that much. You may not agree with this, but it is what they are saying.

> High levels of V. destructor associated with treatment failure caused by acaricide resistance, unusual fall and winter weather that affected mite and bee population growth patterns, timing of treatments, forage for bee populations or fall feeding of colonies in preparation for winter and / or in the spring build-up period, and in some cases presence of Nosema spp. may have been a contributing factor.  
 
> These stressors interacting in combination with each other affected colony survival, but direct and indirect effects associated with acaricide resistance and the failure to control V. destructor mites are believed to be the most important factors related to colony loss in Canada.
 
Honey bee colony losses in Canada
Robert W Currie, Stephen F Pernal and Ernesto Guzmán-Novoa
Journal of Apicultural Research 49(1): 104-106 (2010) © IBRA 2010
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