Hygiene-eliciting brood cuticular hydrocarbon mixture as a tool for determining honey bee colony pest and disease-resistance

Despite numerous management and breeding interventions, the ectoparasitic mite Varroa destructor combined with the pathogens it vectors remains the primary biological threat to honey bee (Apis mellifera) health.  Hygienic behavior, the ability to detect, uncap, and remove unhealthy brood from the colony, has been selectively bred for over two decades, and continues to be a promising avenue for improved Varroa management.  Although the hygienic trait is elevated in many Varroa-resistant colonies, hygiene does not always confer Varroa-resistance, as some hygienic colonies still require miticides to limit mite infestations.  Additionally, existing Varroa-resistance selection methods tend to trade efficacy for efficiency, because those achieving the highest levels of Varroa resistance can be time-consuming and thus expensive and impractical for commercial use. Here we demonstrate that a mixture of synthetic honey bee brood compounds associated with Varroa and/or Deformed-Wing Virus infestation can be used to trigger hygienic behavior in a two-hour assay.  Colony hygienic response to this Unhealthy Brood Odor (UBO) assay is negatively correlated with mite infestation, and positively correlated with removal of experimentally introduced mites.  Colonies that score higher on the UBO assay are also more likely to overwinter successfully, possibly as a result of having lower Varroa loads.  We discuss the relative efficacy and efficiency of this Varroa-specific assay as a tool for facilitating apiary management decisions and for selection of honey bee colonies more resistant to Varroa.