Hyperthermia treatment can kill immature and adult Varroa destructor mites without reducing drone fertility

In the last few decades, different hyperthermia devices have been developed to kill Varroa destructor mites in the colony. Intriguingly, effects of hyperthermia on Varroa destructor and honeybee brood have hardly been investigated. We exposed honeybee brood to temperatures of 41°C to 45°C to investigate effects on Varroa destructor in the hive and on drone fertility of treated colonies. Drone fertility is an important issue in keeping healthy and viable honeybee populations. We show that temperatures of 42°C for 3 hours or higher kill all the Varroa destructor but, unfortunately, also part of the honeybee brood. Temperatures below 42°C are ineffective against adult Varroa destructor. A temperature of 41°C and 2 hours duration is highly effective against immature Varroa destructor and thus interrupts their reproduction without harming the viability or fertility of drones, while longer durations or higher temperatures kill the spermatozoa of the drones.