We don`t winter the bees in the Black Forest. I look for it that when the coolness and dampness comes to the Black Forest - and the good flows of pollen and of a little nectar (from flowers) cease, I move to mild regions sort of like yours where the bees can still forage a little bit and fly long. That is where they make the Fl?lingsbl?tenhonig next April and May. This year I "ran away" mid-September from the on-going pine-flow. Usually I move October.
Only when and if the forest flows End of May, beginning of June, I move our bees to the BF again.
Just my little hobbyiest-setup by the house stays put all year long. Quite a different keeping of bees, I must say. Keeping bees in the milder, flower-flow-dominated regions is just so much easier.
So all in all, apart from us moving our bees, the conditions are pretty much the same for you and me.
No matter where and when I used thymol, the effect was to be neglected. A friend of mine - I got my first bees from him - used it with some effect. But he kept on loosing hives just the same, so....
What I mostly do, last honey-pull latest mid-August: Take ALL brood- combs away in the brood-box ( which has room for 9 frames Dadant, they hover around 6 to 8 usually), including the queen. Shake off maybe half the bees. Put the queen and about three good frames of brood in a nuc-box. Take it to another yard. Treat the nucs with formic acid (sponge cloth, a strong hive hardly has any damage from this as the treatment is over in a matter of hours - ratio of bees to room is what I mean with "strong"), as they have most of the mites.
Treat the leftover bees (which have been given a new queen by now and have no honey-supers any more) with oxcalic acid vaporization after a few days. This year I skipped that part.
If this is done in July still, I might get away with all natural comb in the brood-boxes of nucs and left-behing-bees (both having some combs - the nucs about 3 brood-combs, the hives about 2 honey-combs), which they build nicely at this time of year. But it stresses the bees at this moment. If this is done mid-August or so, I prefer foundation or a mixture of foundation-less and foundation, as the bees won`t have enough places to store feed otherwise.
Mostly, end of September, beginning of October at the latest, all get another round of sponge-cloths with formic acid. I worked with individual treatments in the last years, but now all get the same treatments, as the results where not good otherwise.
This year I only did the last treatment, as there where little mites and a honey-flow.
The next days I will vaporize once (if need be I would do it twice, not this year), dribble on some maybe.
I don`t cull any drone-brood and neither did I ever cull any worker-brood. I as yet always have been vigilant enough to be able to avoid that.
With this rough outline (flexibility is part of the plan) I haven`t lost a single unit to the varroa mite for two winters now. I don`t really expect any losses due to varroa this winter, either.
merry christmas to all - all over the world!