>I understand that you don't treat for varroa, but as a first time beekeeper, they scare the !@#$ out of me. I have two TBHs built, both with solid bottoms, and am struggling with how to deal with varroa, which I am told will be coming.
Once the bees are down to 4.9mm in the core of the brood nest I have not seen any issues with Varroa. I would not count on the Varroa "coming".
> Screened bottom advocates say that not only do the mites fall through the screen throughout the year, but with periodic sugar dusting the varroa can be kept to a manageable level.
There are plenty of studies that show both SBB and powdered sugar to not be effective at Varroa control. I'm not saying they are or are not, but it is questionable. My experience is the SBB made no difference in the Varroa one way or the other. I have never used powdered sugar nor have I ever used drone trapping. Drone trapping will just breed Varroa that prefer workers and waste a lot of resources the bees need.
>I DO want to avoid using chemicals as mite control, so how do first year beekeepers, with solid board bottoms, handle varroa the first year or two, until they get to the point where the bees are more or less handling it themselves?
My experience is that Varroa has everything to do with cell size, not genetics.
> Sugar dusting isn't feasable with solid bottems, is it?
I don't think it's very feasible with screened bottom boards... but I suppose the screen would be helpful for sugar dusting.
> I understand that smaller cell size helps
I my experience it was the ONLY thing that helps.
> but am also told that it may take several generations for the bees to regress to the smaller size.
I have put package bees in a top bar hive and gotten everything from 5.1mm to 4.7mm in the core of the brood nest. 5.0mm probably will deal with Varroa and 4.9mm certainly does. It MIGHT take more than one turnover of comb. Generations of bees are a different matter. No matter how many of them you raise in large comb, they won't get significantly smaller until the smaller bees draw new comb. But they might be small enough on the first try. They might not, and then you may need another turnover of comb. Two is usually sufficient. Sometimes it takes three.