I have lost both of my hives this winter for some reason. One hive was weak going into the winter so I thought it would die, but the second one was strong last year. I talked to a local beekeeper and he said it was due to the trachea mites. He also told me how to treat them with chemicals. I would prefer to not use chemicals if possible. I know about the screened bottom board and the 4.9 mm cells for verroa mites, but don't know of natural ways for trachea mites.