Selection of Honey Bee (Apis mellifera) Genotypes for Three Generations of Low and High Population Growth of the Mite Varroa destructor

Honey bee (<i>Apis mellifera</i>) population declines have been associated with the parasitic mite, <i>Varroa destructor</i>, which is currently primarily controlled by the use of acaricides. An alternative is to breed for resistance to <i>Varroa</i>, which was conducted in this study by bidirectional selection for mite fall to obtain colonies with low (resistant) or high (susceptible) <i>Varroa</i> population growth (LVG and HVG, respectively). Selection for three generations resulted in approx. 90% lower <i>Varroa</i> population growth in LVG than in HVG colonies. In addition, late summer <i>Varroa</i> infestation rates of brood and adults were both significantly lower in LVG colonies (<i>p</i> < 0.01), which was also significantly associated with lower Deformed Wing Virus (DWV) infection levels (<i>p</i> < 0.01). Survival of <i>Varroa</i>-parasitized bees was almost 50% higher for LVG bees compared to HVG bees (<i>p</i> < 0.01). Also, colony winter survivorship was significantly higher for LVG colonies than for HVG colonies (<i>p</i> < 0.05). However, the higher colony populations observed for LVG colonies were not significantly different from those of HVG colonies. Overall, individual and colony health was improved by selecting colonies for LVG, demonstrating its effectiveness as a means of breeding for controlling <i>Varroa</i> populations in honey bee colonies.