A derived honey bee stock confers resistance to Varroa destructor and associated viral transmission

Authors: O'SHEA-WHELLER, THOMAS - Louisiana State University; Rinkevich, Frank; DANKA, ROBERT - Retired ARS Employee; Simone-Finstrom, Michael; Tokarz, Philip; HEALY, KRISTEN - Louisiana State University

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/23/2022
Publication Date: 4/7/2022
Citation: O'Shea-Wheller, T.A., Rinkevich Jr, F.D., Danka, R.G., Simone-Finstrom, M., Tokarz, P.G., Healy, K.B. 2022. A derived honey bee stock confers resistance to Varroa destructor and associated viral transmission. Scientific Reports. 12(1). Article 4852. https://doi.org/10.1038/s41598-022-08643-w.
DOI: https://doi.org/10.1038/s41598-022-08643-w

Interpretive Summary: Parasitism by the Varroa mite is the leading cause of honey bee colony losses. Miticides and Integrated Pest Management practices are often used to reduce Varroa infestation, but high cost, inconsistent outcomes, and reduced efficacy raise the demand for a sustainable solution. Breeding efforts to create a stock of honey bees that reduces Varroa populations by selecting for bees with high levels of Varroa-Sensitive Hygiene (VSH) behavior have been performed under controlled and isolated situations. This research determined the feasibility of utilizing a stock of bees with VSH in a migratory beekeeping operation. Results showed the bees with high levels of VSH had reduced annual colony losses due to reduced Varroa infestation and levels of pathogenic viruses transmitted by Varroa compared to a commercial stock. These results show that bees with VSH behavior are a viable option to high levels of Varroa control and annual colony survival in a migratory beekeeping operation.

Technical Abstract: The ectoparasite Varroa destructor is the greatest extraneous threat to managed honey bee (Apis mellifera) colonies globally. Despite significant efforts, novel treatments to manage the mite and its vectored pathogens have shown limited efficacy, and existing acaricides face growing physiological resistance. A prospective solution lies in the development of Varroa-resistant honey bee stocks, but a paucity of applied, consistent, and rigorous performance data stands as a barrier to more widespread adoption. Here, we characterised the performance of a Varroa-resistant honey bee stock, designated ‘Pol-line’, using a large-scale longitudinal field study, within a commercial pollination operation spanning three climate regions. Our results demonstrated markedly reduced Varroa levels in this stock, diminished titres of three major viruses (DWV-A, DWV-B, and CBPV), and equivalent colony productivity when compared to a standard commercial honey bee variety. These favourable health parameters were associated with a more than two-fold increase in colony survival over the course of the study, tantamount to that achieved by chemical acaricide treatment. Additionally, by tracking all 366 colonies individually, we evaluated the explanatory power of Varroa levels and viral titres in determining colony mortality risk, and found that while Varroa levels were an effective predictor, viral titres did not constitute strong independent indicators. These findings highlight the need for reassessment of the damage caused by Varroa mites per se, and have significant implications for diagnostic and treatment methodologies. In sum, our data demonstrate the successful utilisation of Varroa-resistant honey bees in a functional commercial operation, and indicate that the current understanding of Varroa-mediated colony loss should be reconsidered. This suggests that further development of derived stocks represents a tangible, integrated, and logistically tractable solution to the global issue of honey bee losses.