Re: Treating within a resistance raising system
Mike, I would be very happy to see you succeed. Just to know that you were able to develop mite tolerant bees and successfully keep them would be an extremely happy occasion.
With that said, what Juhani has done is 3 or 4 steps ahead of where you are. You could benefit from his hard work by getting 2 or 3 queens from him and seeing how they perform under your conditions. I would not under any conditions recommend supplanting your working stock, there are too many important genes in your bees. But if you can tilt the table in your direction just a bit, it will go a long way to increasing your likelihood of success.
That figure comes from a time in the early 1990's when we were first dealing with varroa mites here in the U.S. and a report was made from Florida of finding exactly 1 survivor colony out of 10,000 in a large beekeeping operation. It was a Carniolan queen if that helps. Susceptible to me means dead bees. I have never seen a colony live for very long at the tipping point. Either they control the varroa or the varroa decimate the colony.
Where does that 99.99 figure come from? Did you just make it up? What does 'susceptible' mean? It will affect them to a degree? It will kill them?
To address your posit of cleaning bees of varroa and then giving them a new queen. In my opinion, Juhani is correct. You are tilting the balance away from finding mite tolerant bees and reducing the number of colonies that are actually being tested the hard way for mites. This is why I made the statement earlier about requeening being the only thing I would do if a colony were collapsing from mites. Unfortunately, as Squarepeg pointed out, this is likely to occur very late in the fall or very early in the spring when requeening is difficult or impossible given that you have to rear new queens. My experience is that it is best to let the susceptible colonies die and split the survivors.
Here is what I know works. Find some tolerance. Set up an isolated population and breed from the tolerant queens. If you do the hard work of checking mite loads in colonies and identifying the colonies that are least affected, and raise queens from those least affected colonies, in time you will produce mite tolerant bees. It will not be fast. You won't succeed in 5 years. You might succeed in 10 years. Meantime, consider bringing in some known tolerant genetics. They are available and would jump start your program.
We saw the first varroa in 1990. By 1993, they had spread U.S. wide. I lost all but one colony in the winter of 1993/1994, i.e. about 25 Buckfast colonies died. The lone survivor was a feral swarm I had caught the previous year that showed very high levels of Apis Mellifera Mellifera traits. They had no real mite tolerance, but survived probably because of the brood break from swarming. I split that colony into 3 in late March and managed to make a small crop of honey. Those bees were treated for mites in the fall and I treated every fall until 2004. There were NO feral bees to be found from 1994 to 2000. I checked diligently for feral colonies and did not find any anywhere. By 2003, I was seeing a few feral swarms. I caught a few in 2004, one of which turned out to show distinctive mite tolerance along with a host of unwelcome traits such as excessive stinging. I inspected all of my colonies thoroughly in the fall and found that colony had almost no varroa in the drone brood. This translates to a small bounce back by feral bees after 10 years of exposure to devastating levels of varroa.
I tilted the balance in my favor by purchasing 10 queens from Dann Purvis. While I am confident I could have gone forward with the limited stock I had, there would have been problems with inbreeding. By using the Purvis queens as a drone source and the mite tolerant swarm queen as a source of eggs, I was able to raise queens that were highly mite tolerant and had very little inbreeding. There is no rocket science in this. I simply stopped treating. From the winter of 2004/2005, I have not in any way treated my bees. They either live or they die. I split the survivors. For the last 3 years, I made up losses by catching swarms, many from my own bees, others from feral colonies derived from my bees. My average winter losses have been about 2 or 3 colonies per year out of 10 to 20 colonies. This is in the range of losses pre-varroa.
NW Alabama, 46 years, 24 colonies and growing, sideliner, treatment free since 2005, 14 frame square Dadant broodnest