I checked my back yard top bar hive which was started with a feral swarm. It seems to be doing well, though it has stopped expanding after filling about two thirds of its four foot length. I have harvested about a bar of honey over each of the last two months, and added a bar to the brood nest 4 times. Yesterday I pulled a heavy bar of capped honey--the bottom third was drone comb. I was a little surprised to find 2-4 mites on each of the drone larvae.

I haven't done an alcohol wash. Does the count in drone brood correlate with a dangerous level of varroa indicating need for treatment? How effective is drone comb culling in controlling mites?