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It I very good that you want solution to problem.
Oxalic acid violated brood. Thymol and formic acid are good brooding time treatments.
When you see free mites on bees' body, situation is bad. It is better to treat now than wait to September.
AS is easy to treat. It is better to use Apiquard (thymol) Oxalic acid violates brood.
Then there is brood part of AS. It is better to wait 2 weeks more that all bees emerge and you may kill mites with thymol. Keep treatment on all the time.
There is a Ducth method, that you make again an AS and there is part of colony where is no brood. You kill mites and join to first swarm. It does not differ much if you wait that whole hive is broodless, and mites are was to kill.
Hive is not big, and mite will destroy the colony before Winter if you do not nothing.
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