Thanks for the clarification, Medhat--the amount of brood present has a profound effect upon overall efficacy. > >The shared paper mentioned few modes of action on how OA kills mites. > Actually, the authors state only that "OA appears to combat varroa in two ways. It damages varroa mouthparts and also causes increased bee to bee contact and grooming." The authors cite a few papers in support of the above statement, which surprised me, since I hadn't noticed support for either claim when I read the original papers when they came out. So I reread the papers this morning (and also searched for the words "damage" and "mouthparts"--none of them mentioned damaged mouthparts or increased contact. As noticed by Aliano and Ellis in one of the cited papers: "The mode of action for OA is not completely understood." And now, some 11 years after that statement, as far as I've seen, the mode of action is not in any way understood, and any claims as to its mode of action appear to be merely speculative. -- Randy Oliver Grass Valley, CA www.ScientificBeekeeping.com *********************************************** The BEE-L mailing list is powered by L-Soft's renowned LISTSERV(R) list management software. For more information, go to: http://www.lsoft.com/LISTSERV-powered.html