P. Michael Henderson
A friend contacted me about his hive. He went out to the hive one day and the bees were gone. He couldn't figure out what had happened.
While I couldn't examine the hive, I can guess what happened. He probably had European bees and was not monitoring the varroa load in the hive. When a European hive is not treated, the hive will generally survive through the summer because the hive is expanding. But when fall comes, the hive starts to contract (less bees for over winter) but there's the same number of varroa mites. The mite load is so bad that every brood bee is infested and damaged.
When it gets that bad, the bees will decide that their present hive is untenable and decamp (abscound).
If people know you keep bees, you may get a call in the fall about a swarm in one of their trees. Don't bother. That "swarm" is probably a hive that was infested with varroa. If you pick it up, the hive will just go through the same cycle - unless you're going to treat for varroa. One day you'll go out to the hive and it will be empty. When you get that call about a "swarm" in the fall, politely decline.
Wait until spring to pick up swarms. Even then, you can't be sure what kind of hive you're getting. People who keep European bees, and treat for varroa, have swarms. If you pick up a swarm from a European hive and you don't monitor and treat for varroa, they will abscound in the fall (this is called a "varroa bomb" because they will drift and infect other hives).
If you want to keep bees that do not require treatment, you have to take your losses. Some of the swarms will be sufficiently Africanized that they will be able to deal with the varroa and those are the hives we want to encourage and keep.
When you get a good hive - relatively docile, able to deal with varroa, and good honey producers - split that hive in the spring and make two hives of it. That way, you will be contributing to the overall health of bees in your area. If one of those hives swarm and you don't capture it, that hive will either be captured by another beekeeper, or they will set up in a feral location. Either way, the drones from your hives and the swarm hive will spread the "good" genes.
Beekeepers who continue to keep European bees just contribute to the varroa problem. If no one kept bees, the wild bees would have already evolved to coexist with varroa - all hives that couldn't coexist would have died. As Pogo said, "We have met the enemy and he is us."