My bees are recently returned from almonds.  I follow much the same treatment rotation as Randy:  Apiguard in August, oxalic dribble in December, oxalic dribble after divides in springtime, and formic in summer.  Most of my doubles are busting at the seams now.  On a few mite washes last week I saw mite washes in the 15% range- very troubling.  So was it mite bomb from the neighboring colonies in the almonds?  Or is it possible that due to our unusually warm December with very abundant pollen, that they never went broodless, and the mites 'piled into' the capped brood and escaped oxalic treatment?  I know theres no definitive answer from the group, but wondering if there is a known limit to how many mites will invade a brood cell, if there is a limited amount of brood. 
Brion
Nevada City, CA

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