Last night I went to my 2nd meeting of the Greater Cleveland Beekeepers' Association meeting. The speaker was the editor of Bee Culture magazine (no talk of new shoe styles for the season, sigh...), Kim Flottum. Surprisingly, he lives in Medina County! The title of his talk was "Keeping Healthy Bees."
For 2-hours Kim told us about viruses and diseases and showed sick bees. The biggest problem for us backyard beekeepers is the varroa mite. It's rampant and can take over a hive if not watched. It doesn't carry diseases, but its bite stresses out the bee (duh!), which weakens the bee's immune system, which then allows all kinds of terrible things to happen.
What to do: Spend 60% of my time controlling them. This means measuring how many of them every few weeks, trapping the Drone bees (gotta learn more about that), and heavily dusting the inside of the hive with powdered sugar! It makes the bees too slippery for the mites to hang on to. Plus the bees love it!
I like that what Mr. Flottum suggested was not using chemicals or antibiotics. These generally aren't good for us and they're not good for bees.