A longitudinal study of viral interactions in honey bees during the California almond bloom

Honeybees participate in an annual mass human-mediated intercontinental ‘migration’ where over half of all commercial honeybee hives in the United States are shipped to California to pollinate most of the world’s almonds. Interactions with hives from across the country have the potential risk to spread novel infectious diseases and variants through the honeybees and spillover into wild populations. This early mass bloom provides the first major food source for honeybees emerging from winter, and pollination services account for substantial income for commercial beekeepers. It is essential to weigh the advantages of participating in the almond bloom against the risks of disease in bees. We conducted an observational longitudinal RNAseq study of viral diversity within honeybee colonies from a single beekeeping operation as they participated in almond pollination compared to control hives. Surprisingly, viral diversity did not significantly change for the hives that participated in the bloom, and there were not significantly more viruses after the bloom. Many viruses had similar patterns to control hives, suggesting seasonal dynamics that occur regardless of the bloom. There was also no evidence of particular viruses dominating the viral community as a ‘superspreader’. We argue that the inundation of floral resources means that honeybees could minimize their indirect interactions on flowers. High losses in the winter before the almonds bloom are economically impactful to beekeepers but may also differentially cull hives that harbor the most virulent pathogens. This suggests that the early food resources that the bloom provides may outweigh population-level infectious disease risks.