We do not treat any of our hives with miticides, antibiotics, or other medications. This prevents the buildup of chemical residues and promotes selection for a mite resistant strain of bees. We have started to focus on selecting for mite resistance as opposed to mite tolerance. Mite tolerance is the ability of a particular strain of bees to survive even with a heavy mite load. Mite resistance is the ability of a strain of bees to keep mite levels in the colony low by a number of different mechanisms. Pure ‘Darwinian’ selection does not differentiate between tolerance and resistance. With the spread of some novel and virulent viruses 2-3 years ago, mite tolerance no longer seems like a good option for breeding. Viruses can mutate much faster than the bees can develop resistance to them. We now select breeder queens by taking samples and counting mites from every potential breeder colony in the operation. Breeders are selected from those with the lowest mite counts, highest honey production, nicest patterns, and best behaved workers.
In mid summer, mite counts are done on every colony. Colonies with high mite counts are removed from consideration as breeder colonies, and are split and requeened to break the brood cycle and reduce mite levels. We may try sugar dusting these colonies as well. The goal is to catch them before the mite levels reach a point where the viruses cause a colony to collapse and infest other colonies with mites.
In your management of our bees please bear in mind that these bees are mite resistant, not mite proof. Some type of mite management will most often be needed to keep survival in an acceptable range. In experiments, our bees generally have 10-20% winter loss when mites are managed by the drone brood trapping method. To us this is quite acceptable. You could also experiment with powdered sugar dusting or some of the ‘benign’ soft chemicals. We tried the sugar dusting for a season on a handful of colonies with good results, but have not experimented with any chemical treatments. Sampling for mites towards the end of summer to determine if a treatment is needed is an excellent idea. Some colonies managed with drone brood trapping have had zero mites in the sample, others are high enough you would likely want to treat. It can depend on many variables, including your specific management, the season, how carefully you kept up with the drone removal, your location and who else has bees near to yours.