I came across an interesting short article in the August issue of American Bee Journal. The article indicated that varroa mites have a lower tolerance to heat than honey bees. Using this information a European has invented a hive which utilizes solar energy to raise the hive temperature above the level which the mites can tolerate. After several hours at the elevated temperature the mites in the hive are killed; both those in brood or attached to bees. The bees are unharmed. At this point the thermosolar hive is in low volume production. The inventor is trying to get crowd funding to expand the production. For more information go to the following link:
Whether this will become another arrow in the anti-varroa arsenal only time will tell.