I might expect a couple hundred, hopefully less. It depends on efficacy of thymol treatment, date treated, and seasonal conditions since then.
You should now have virtually none to kill off, so no point in risking your bees with further interference, acid mortality (or even colony mortality due to a combination of oxalic treatment and nosema, for instance).There are sufficient alternatives available for me, when the bees are getting into spring expansion and later...
Last year, I picked on a colony which was relatively weak and loaded it with emerging brood from about three colonies I had supicions of having a shade too many mites. I did this over about a week. The weather was favourable and nearly all the brood emerged (might not be so lucky always), so in went the rest of the brood and most of the rest of the mites, from the suspects and the huge colony with all young bees was split, leaving no brood behind (the brood left in with the queen was sacrificed later) and the other bees cleared of most mites when the brood had emerged. All bees back together and huge colonies of bees.
Yes, it required effort. Yes, bees needed to be healthy, Yes, the weather was kind. Yes, I had enough colonies to play with and no, not so many that it was not so practical. Yes, they were all in the same apiary (for transferring brood frames). Yes, my other colonies were busy collecting OSR nectar.
The main reason for all that was that my beekeeping season had ended abruptly, the previous September, and the bees had been 'neglected'/'ignored'/'left to fend for themselves' until spring. None had succumbed over winter, but some were weaker than I would have preferred, going into winter.
After that, there were no further mite problems with those bees all summer. I had considered winter oxalic acid treatment, but deemed it unecessary. I did not consider colony strength at the time, but in hindsight, a couple or four were likely weak at the oxalic 'window' anyway and bee mortality from opening weak colonies in the middle of winter and pouring oxalic over them might have induced some colony mortality.
Yes, Finman will come on and say 'pff, too much effort, etc, etc, etc' but I don't really care. Mine is not a commercial enterprise. The point I am making is that there are other ways. At least a couple of my colonies displayed some signs of nosema for a very short period in the spring as they started to expand. I did not confirm it as they all went away like trains with spring expansion, so nothing really worth worrying too much about.
Those colonies might have had an adverse reaction to oxalic and so I may have lost quite a few through the winter for one reason or another. As I said, there were no dead-outs to deal with, and no oxalic treatments done .
No oxalic, this winter either. I shall await and see what I need to deal with when they start to get going. The plan may well pan out differently this year. I wait and see.
RAB
