>>Therefore, I don't know if complete broodlessness is critical. I don't mind a patch of two of sealed brood when I trickle. OA acts for a few weeks (I am thinking at least 3 weeks) and the last sealed brood will emerge in a few days. My criterion is no eggs and no open brood. >>My money is on a medly of low-kill mechanisms to keep the mites from evolving resistance to any. And I want to have the bees exposed to some mites and viruses they vector as this helps weed out the weaker colonies. Ironically, this is an unintended benefit of varroa. Waldemar -- Visit www.honeybeeworld.com/bee-l for rules, FAQ and other info ---