I'm delighted with a 'surfeit of advice', it's much, much better than not getting any at all. It gives me plenty to think about, and helps balance the pros and cons of the various alternatives.
Thanks also for the Apivar information.
Here's a bit more background info, which might help explain why we used Apistan.
"Full of varroa" was probably the wrong term to use. It was, initially, an assumption because of their generally poor condition, and taking other things into consideration. The bees were very small, which could have been because they were hungry (close to starvation), or because of infestation.
The previous beekeeper had used Apiguard, but we couldn't tell how carefully they had followed instructions. Pre-Apistan the drops were 1 and 3 per hive, per week. They were not treated with Oxalic Acid, so the Apistan was for insurance, as much as anything else.
I'm not wriggling, disagreeing or arguing, but we chose Apistan quite carefully. The most recent Beebase data for resistance is from 2010, when only two areas reported back. Both were green. Prior to that, running back through the maps and also checking the collated data map for 2002 through to 2010, we are in an area that stubbornly keeps a green dot, which suggests no resistant varroa. https://secure.fera.defra.gov.uk/beebase/maps/map.cfm As far as I know there's no other data available, but if there is, I'd be grateful to know where to find it.
I don't know enough about the biological mechanisms, but I believe the mites will only retain varroacide resistance if they need it, because it's 'expensive' for them to do. I don't know how many generations it would take for this resistance to disappear, nor how long it would take for it to be resurrected from their gene pool, if that was possible.
Back to the question - the idea of freezing the frames was to kill any spare varroa and to use the stores rather than either burning them or throwing them away, because it seems a waste. We only have space to do 2 at a time, so had considered using sulphur, to do the whole lot in one go, but as far as we know it doesn't penetrate cappings, so wouldn't kill mites inside the cells. I don't know how long they survive off the host, or after the death of bee larvae.
The inspectors like shook swarms, because it gives the bees a clean start. It does seem brutal and wasteful, and we're still swinging between doing this and a Bailey comb change. It's probably one of those decisions that will finally be made 'on the day'.
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