this with apibioxal, if yes what time of the year
Yes, ApiBioxal is one approved product to use, and usually after honey is taken off in late summer, but you can sublimate at any time. For example, one vaping on a swarm that arrived recently will knock down the majority of the mites before brood is laid.
By late summer colony size will have diminished and drone larvae absent (varroa prefer the longer drone gestation period), but the varroa population doubles every 3 weeks, and varroa will feed instead on worker brood and become a real threat to the production of healthy winter bees, between late summer and early winter.
As BC said, the main ingredient of ApiBioxal is plain ol'
oxalic acid dihydrate, aka the OA you can buy online cheaply to clean wood & boats and all sorts. Chemicals Laif added sugar, which caramelises in sublimators, and silica which keeps the crystals flowing but is also a nuisance in a sublimator. Naturally, it is not so cheap.
Plain OA was used for many years by beekeepers (and bee inspectors, on their bees) until a commercial version was approved (costing £30k+) by the UK Veterinary Medicines Inspectorate with the support of the BBKA. At this point it became an offence to use plain OA, though it is hard to see how a beekeeper might be caught, let alone prosecuted.
If you intend to buy a sublimator, have a search here for threads on the
GasVap at one price point, and the
Sublimox at another. What is not negotiable is the need for an
effective mask to protect breathing and eyes from particulates and organic vapours.