Re: treatment free beekeeping - the risks
pedro, i believe it is generally accepted that most hives have a least some mites, so i don't think we're talking about completely isolating a healthy hive from mites.
and i'm not sure how a healthy hive would come in contact with unhealthy hive in any other way except robbing. in what other ways are you considering?
if i a hive is being robbed, it has been weakened. perhaps by an overload of mites, which could hitch a ride back to a healthy hive, and maybe pushing the mite load in the healthy hive above tolerance.
in varroasis, the bees in the sick hive may have also succumb to virulent pathogens, which would also be brought back to the healthy hive.
beekeeping since june 2010, +/- 20 hives, tf