Seasonal and environmental variations influencing the Varroa Sensitive Hygiene trait in the honey bee
Résumé
The invasive miteVarroa destructor is identified as the main biotic cause of European honey bee colony losses in many regions, leading to systematic treatments of colonies every year in order to prevent colonies from collapsing. However, some colonies have been reported to survive in the absence of treatment. The ability of honey bee colonies to survive varroa mite infestations has been associated with the development of Varroa Sensitive Hygiene (VSH) behavior. Colonies displaying VSH are able to detect the presence of varroa through the cap of developing brood cells and to remove the parasitized brood. To improve breeding programs for varroa resistance in apiculture, detailed knowledge of the mechanisms that enable bees to survive mite infestation and environmental conditions that can influence the expression and phenotyping of VSH behavior are needed. This study evaluated the influence of the genetic origin of the colony, the colony population dynamics, varroa density, and food supply on the ability of colonies to express the VSH trait. First, we found that varroa-selected colonies displayed lower varroa population growth rate. We also revealed that the genetic origin of the colonies and the month during which the test was performed had a significant impact on VSH behavior, with varroa-selected colonies showing higher VSH abilities than unselected colonies, and especially at the end of summer. Finally, we showed that sedentary varroa-selected colonies expressed higher VSH activity than colonies placed on lavender fields during active honey flow. Such findings are particularly important to standardize testing for varroa resistant colonies in different locations, a feature that is essential to ensure the success of breeding efforts.