The evidence offered is that almonds have a low protein content, and more than half the hives in the USA end up in California performing almond pollination each year. CCD meant that there were not enough bees to pollinate the almonds and contract prices went from $35 per hive to about $200 per hive. This caused many beekeepers to feed their bees supplements to keep them healthy to chase those higher fees. The protein supplements introduced into the bees' diets appear to have led to a surplus of bees available for this year's almond pollination.
This year’s Californian bee glut, then, has been caused by a mixture of rising supply meeting falling demand. The price of almonds dropped by 30% between August and December last year, as people had less money in their pockets. That has caused growers to cut costs, and therefore hire fewer hives. There is also a drought in the region, and many farmers are unlikely to receive enough water to go ahead with the harvest. Meanwhile, the recent high prices for pollination contracts made it look worthwhile fattening bees up with supplements over the winter. That may help explain why there have been fewer colony collapses.
The rise and fall of the managed honeybee, then, owes as much to the economics of supply and demand as it does to the forces of nature. And if the nutrition and disease theory is correct, next year’s lower contract prices may see beekeepers cutting back on supplemental feeding, and a resurgence of CCD.
Again, I can't speak to the merits of this "diet centered" argument, but it does not seem completely absurd to me. My bees have had no CCD related problems, but in Maryland we have really good pollen sources.
