I think we know what key factors interact, and I think their interactions are very much dependent on the region, the severity of weather, for example, the crop systems, but the facts that you mentioned are essentially the leading culprits. We have a very complex system now of introduced diseases and parasites, which are more difficult to manage. Canadian beekeepers do have tools to use them, and by and large if management is good, that does quite a lot to try to keep these parasites and pathogens in check.
Certainly, exposure to pesticides is very much dependent on the crop system, the region of the country, and that can have a greater or lesser extent on colony survival, as does nutrition. We can have bees in areas of the country which have good nutrition most of the year and others that don't. I think the key is trying to elucidate, as you suggest, the interaction of these factors, which is perhaps the biggest push, if you will, towards colony survival, especially over winter.
Within AAFC, we're actually running a study like that right now, trying to look at the interactive effects of supplementary nutrition on honeybee colonies and disease treatment to see which of those two factors may in fact be the biggest influence in colony survival, particularly over winter.