Oxalic acid - trickle or vape

The title is a statement, not a question.

With a couple of provisos it doesn't matter which method you choose to use, what matters is that you use it.

And, if you are going to treat a colony with oxalic acid in the winter, then it makes sense to try and treat them at the optimal time ... best as far as the bees are concerned that is, which means that it's the worst time for the mites.

The winter oxalic acid treatment has nothing to do with getting your colonies successfully through this winter. That's already largely been determined by the timeliness and efficacy of your late-summer/autumn mite treatment.

Applied early enough, the winter bees will be protected, the colony will be strong and overwinter survival should be pretty good.

However, applied too late and the prospects are less promising.

If the winter bees were exposed to mites during development they will have high virus levels and a short lifespan. The colony may rapidly shrink in size, become too small to thermoregulate properly, and succumb during a cold snap.

Not good. Not good at all.

So, if a winter oxalic acid treatment is nothing to do with surviving this winter, what is it for?

The winter treatment this winter has everything to do with getting your bees through to next winter, as a large, healthy, productive colony.

Which will also help to get them through next winter.

By minimising mite numbers before the brood rearing starts in earnest, the overall number of mites in the colony by late summer next year will be less than they would otherwise be. That will make your interventions next August or September more effective.

A winter oxalic acid treatment should also help minimise miticide resistance.

Think of it as an investment in the future.