The use of airborne ultrasound for Varroa destructor mite control in beehives

The declining health of honey bee (Apis mellifera) populations is of global concern, as they are arguably the most important pollinator insect. The Varroa destructor mite weakens bees by sucking their haemolymph and spreads debilitating illnesses such as Deformed Wing Virus. Current methods of Varroa mite control are usually pesticide-based with potential side effects for the bees or the beekeeper, and can leave residues in the honey or wax. The mites can also develop resistance to these pesticides. The objective of the current work is to investigate the use of high-frequency, high-intensity airborne ultrasound to control the Varroa mite populations using a chemical-free technology. A prototype ultrasonic system that generates airborne ultrasonic waves at different frequencies and intensities was constructed and tested. In initial studies, small transparent enclosures were used to observe directly the effects of the ultrasound on the bees. Preliminary in-hive tests were then conducted. Bee hives with varying levels of Varroa mite infestation were temporarily sealed to prevent bee traffic and then the bees inside were exposed to the ultrasound. The mite drop from the hive was recorded for (i)30 minutes before, (ii)during 30 minutes of ultrasound exposure, and (iii)30 minutes after ultrasonic treatment. The bees in the transparent enclosures exhibited normal behavior and appeared to be unaffected by the ultrasound. Preliminary results from the in-hive experiments indicate a significant increase in the rate of Varroa mite drop after only 30 minutes of exposure to the airborne ultrasound inside some of the hives, with the effect continuing after the ultrasonic system was switched off. Long-term field trials of ultrasonic in-hive systems are ongoing