Two clusters, mites. One cluster, mites. No cluster, mites. Honey, mites. No honey, mites. Mites, mites. No mites, mites. Beetles, mites. No beetles, mites. Bees, mites. No bees, mites. Maybe every hive I lose is due to mites. But at this point, with the analysis I've been given, I don't know how I should know the difference.
Another thought, Nosema. Due to mites. No really, Nosema. Have you done any investigating to see what your Nosema levels are like? Then again, it could be a virus, which mites are a vector for. It could be all three. Send a sample of bees to Beltsville for analysis.