Interesting article on the winter collapses this year. The full story is at the link. I've copied the intro below. https://beeinformed.org/2016/03/08/why-did-my-honey-bees-die/
COMMON CAUSE OF WINTER DEATH IN NORTHERN CLIMATES
By Meghan Milbrath, Michigan State University Extension, March 8, 2016
Beekeepers in northern climates have already lost a lot of colonies this winter. While official counts won?t be recorded for a few months, some trends are starting to emerge. One of these trends is a specific type of colony death. In Michigan, I?ve received so many calls describing the scenario below, that I can describe the deadout before opening the hive, or before the beekeeper describes it over the phone. While I may impress some with these predictive powers, the frequency of these types of losses indicates a real epidemic that is affecting honey bee colonies in northern states.
Characteristics of the common early winter death in northern states:
The colony was big and looked healthy in the fall
A lot of honey is left in the top supers
The cluster is now small, maybe the size of a softball
There are hardly any bees on the bottom board
Near or just below the cluster is a patch of spotty brood ? some fully capped, and some with bees dying on emergence (heads facing out, tongues sticking out).
If you look closely in the cells around the brood, you will see white crystals stuck to the cell walls, looking like someone sprinkled coarse salt in the brood nest.
You don?t have records showing that varroa was under control.
We see this classic set of symptoms over and over in the states with a proper winter. A big colony that seems to just shrink down and disappear. Many people want to use the term colony collapse for this type of death, and while collapse is a good descriptor of what happens, this is not true colony collapse disorder. This is death by varroa associated viruses