One of my two colonies (bought as nucs last summer) had really bad chalk brood so I treat it with thymol last learning as I felt it was at a level that would hamper winter preparations. This seemed to help and they got through the winter fine and started building up well too, however at the last inspection the chalk brood was back with a vengeance. I think this queen is for the chop!
Interestingly/coincidently/completely unrelated (delete as appropriate) this colony has had a very low varroa count, consistently zero natural fall!

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