Defining Mechanisms Underlying Mite Tolerance and Honey Bee Survival

View the project final report

Commodities

• Animals: bees

Practices

• Crop Production: beekeeping, pollinator health
• Education and Training: mentoring

US beekeepers lose an average of 40% of their colonies each year, causing economic strain on beekeepers and threatening agricultural production. Uncontrolled infestations with parasitic Varroa destructor mites drive winter losses in temperate regions, including the Northeastern US. A major reason for Varroa’s negative effects on bee health is that it transmits Deformed Wing Virus (DWV), which significantly weakens individual bees and colonies. As there are no treatments for viral infections, beekeepers rely on miticides to control Varroa populations in an indirect attempt to limit the impacts of viral infections. However, a handful of bee populations, including feral bees in the Arnot Forest of New York, have adapted to survive Varroa without any human intervention. While these bees seem to have behavioral adaptations, which may reduce Varroa population, it is also possible that the viruses in this bee population have been selected for reduced virulence. Such selection would occur under conditions of reduced viral transmission, within and among colonies. To explore the role of transmission rates on DWV selection and virulence, I will (1) select DWV populations under laboratory conditions mimicking Varroa transmission and (2) examine natural viral populations in feral Arnot Forest bees, compared with nearby managed honey bee colonies. I will examine the virulence of these viral populations under controlled conditions, and correlate variation in virulence with variation in viral genotype. These studies will elucidate how transmission rates influence selection for viral virulence, and provide insights which can be applied to managing bees for Varroa tolerance.

I will use two systems in which to examine how transmission rates influence selection of different genotypes of DWV (different strains) and virulence of these strains (as measured by mortality rates of infected bees). (1) Determining if rapid transmission selects for more virulent viral populations, by a) Generating populations of viruses that have been selected under conditions of rapid transmission in the laboratory, mimicking repeated transmission by Varroa b) Evaluating if these viruses exhibit increased levels of virulence in laboratory assays, relative to non-selected viral populations c) Determining if this variation in virulence is associated with underlying viral genetic variation by conducting whole-genome sequencing of the viral populations (2) Determining if viral populations in feral bees from the Arnot Forest have reduced virulence relative to managed honey bees, by a) Collecting viruses from feral bees and bees from nearby managed apiaries b) Sequencing viral populations to identify genetic differences associated with these isolated populations c) Assessing virulence of these viral populations Objectives (1a) and (1b) will be completed prior to the start of this proposal. Objectives (1c) and (2a-c) will be completed using the proposed budget, if funded. Results will be used to understand how viral populations can be managed to improve honey bee survival and adaptation. Furthermore, this work will be disseminated to researchers and beekeepers through publications and conferences, help develop outreach activities, and support undergraduate research experiences.