The Business of Honeybees

Scientific American, via Big Picture Agriculture:

In all, more than 31 billion honeybees converge on California’s Central Valley each February to pollinate the almond trees. By the end of the bloom, having gathered plenty of nectar and pollen to feed their colonies, the honeybee population in the orchards may exceed 80 billion. These are the kinds of numbers you need when you're dealing with something like 2.5 trillion flowers, each of which likely requires several visits from pollen-laden bees to produce a nut. Each year, California produces between 50 and 80 percent of all the almonds harvested worldwide; this year California’s orchards are expected to yield 1.85 billion pounds of almonds, which works out to about 700 billion individual almonds. Every almond grows from a successfully pollinated flower, but the bees likely pollinated far more than 700 billion flowers this past spring. An almond tree can only support and nourish so many nuts, so in April and May the trees shed as much as 15 percent of their almonds, depending on the year.
After the almond bloom some beekeepers take their honeybees to cherry, plum and avocado orchards in California and apple and cherry orchards in Washington State. Come summer time, many beekeepers head east to fields of alfalfa, sunflowers and clover in North and South Dakota, where the bees produce the bulk of their honey for the year. Other beekeepers visit squashes in Texas, clementines and tangerines in Florida, cranberries in Wisconsin and blueberries in Michigan and Maine. All along the east coast migratory beekeepers pollinate apples, cherries, pumpkins, cranberries and various vegetables. By November, beekeepers begin moving their colonies to warm locales to wait out the winter: California, Texas, Florida and even temperature-controlled potato cellars in Idaho. The bees stay inside their hives, eating the honey they made in the summer and fall. Several decades ago beekeepers could let their colonies overwinter in a place as cold as Minnesota without worrying about too many bees dying. That's no longer true; in the past 10 years, many American beekeepers have lost between 30 and 60 percent or more of their hives each winter.

I knew the bees spent a bunch of time in California pollinating almond trees, but I had no idea of the massive scale of the operation.  I also had no idea where else they went after that.  I can see how the bees would be worn out and beat to hell after all of that, and therefore susceptible to disease and parasites.