> I'm sorry but it isn't so that in Europe 'everyone treats his/her colonies freely with OAV in the presence of honey to harvest', on the contrary it is strongly discouraged by all official authorities!

It's also discouraged by unofficial authorities ... though I've no doubt that some still do treat with supers in place. Daft if you're trying to produce a high-quality product in my view.

In the UK oxalic acid - as in the pure(ish) chemical - is not a VMD (Veterinary Medicines Directorate) approved treatment. Instead we have to use Api-Bioxal which is doctored with glucose and powdered silica ... weight of which do the vaporiser much good.

My evidence is also anecdotal. I always treat captured swarms 2-3 days after hiving them with vaporised OA (Api-Bioxal). If it's a prime swarm the queen will be laying. If it's a cast she may not even be mated yet. The numbers aren't big, but I've never yet had any obvious queen damage from treatment - virgins still get out and mate perfectly well, even after a good dose of OA.

It's clearly harmful to mites and beekeepers, but bees appear to tolerate it well.

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