Honey bee genetic resistance outperforms a cold-storage induced halt in brood production to control mites and viruses

Authors: Meikle, William; Weiss, Milagra; Adjaye, Daniela; Ricigliano, Vincent

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/13/2026
Publication Date: 3/21/2026
Citation: Meikle, W.G., Weiss, M., Adjaye, D.F., Ricigliano, V.A. 2026. Honey bee genetic resistance outperforms a cold-storage induced halt in brood production to control mites and viruses. Scientific Reports. 16: article 11782. https://doi.org/10.1038/s41598-026-44701-3.
DOI: https://doi.org/10.1038/s41598-026-44701-3

Interpretive Summary: Varroa mites are one of the most serious honey bee pests in the world, because they parasitize bees and transmit diseases, and better control methods are needed. One method is to develop resistant bee lines. Another method is to make existing control easier. This second method involves putting bee colonies in dark, cold storage facilities so that they stop laying eggs and producing larvae. Varroa need bee larvae for reproduction, and because bee larvae develop in comb cells that are sealed on the top the Varroa mites inside are protected from miticides. However, if there are no larvae, none of the Varroa are protected, and the miticides should work better. In this study we compared the cold storage method across different bee lines, two of which were resistant to Varroa. We found that the cold storage method worked to stop brood production and was harmless to colonies, but Varroa levels in hives put in cold storage were not different from levels in hives kept outside (not put in cold storage). However, we also found that the mite resistant bee lines had fewer mites and lower virus levels than the susceptible bee line. This showed that genetic resistance worked well in the field and that might be the best way forward to control Varroa.

Technical Abstract: Varroa destructor mites seriously threaten honey bees by spreading viruses like Deformed Wing Virus (DWV) and contributing to global colony losses. Growing resistance to widely-applied miticides highlights the urgent need for sustainable mite control methods. This study evaluated the impact of a cold storage strategy to decrease bee brood production, and increase mite treatment efficacy, in a commercial Italian bee stock and mite-resistant Russian and Pol-line bee stocks, from prior to cold storage in August until the start of the commercial pollination season the following February. For each year of two years, thirty new bee colonies (10 colonies per stock) were either placed in cold storage (5 °C, darkness, 18 days) starting mid August or left outdoors, and all hives subsequently treated with a thymol-based varroacide. Colony brood area, adult bee mass, hive weight, internal temperature and CO2 levels were monitored during the experiments using periodic hive assessments as well as sensors. Honey bee workers were sampled at different points and evaluated for bee health biomarker gene expression (vitellogenin) as well as virus levels of DWV-A and DWV-B. Cold storage effectively halted brood production but differences in brood levels between groups disappeared within two months, with no long-term impact on population size, mite levels, virus loads, or daily hive weight change. Bee stock was the dominant factor influencing outcomes: mite susceptible Italian colonies had higher mite densities, higher DWV loads, lower vitellogenin expression and higher rates of hive weight loss than Russian or Pol-line colonies. In this study mite-resistant honey bee stocks offered more effective control, reducing mite loads by over 65% compared to the susceptible stock, across both years and both treatment groups of the study, and they have the potential to support honey bee health by reducing reliance on chemical treatments in beehives.