Investigating techniques for successful overwintering of honey bee queens in bulk

View the project final report

Commodities

• Animals: bees

Practices

• Crop Production: beekeeping, pollination
• Education and Training: on-farm/ranch research

Beekeepers in the United States have reported high colony losses for more than a decade. Among many stress factors experienced by honey bees, beekeepers report queen failure as one of the highest contributors to colony loss. Beekeepers can effectively reduce the rates of colony mortality in their apiaries by replacing failing queens, which are available through queen producers. Beekeepers assess their colonies in January and February in preparation for almond pollination services in California. Accompanied by high colony losses, beekeepers may struggle to fill their pollination contract commitments with healthy queenright colonies.

Reports on management practices suggest that the rate of queen replacement by U.S. beekeepers has drastically increased in recent years. This heavy increase in demand for new queens warrants exploring solutions to increase queen supply. One available technique involves overwintering queens in "bank" colonies. For this technique, beekeepers purchase late-season queens and suspend them inside a single bank colony during the winter. After winter, beekeepers can use these queens to replace failing queens in colonies prepared for almond pollination services or introduce them into newly divided colonies after the almond bloom to offset winter colony losses.

We proposed to investigate the technique of overwintering honey bee queens in bank colonies with Oregon beekeepers that pollinate almonds in California. We overwintered queens in bank colonies with three commercial beekeeping operations (September 2020 – January 2021). Bank colonies were assessed for strength (frames of bees, frames of brood), amount of stored honey, and pest and pathogen levels (Varroa mites, Nosema spp.). We sampled queens from these bank colonies for morphometric and reproductive metrics and will compare results from queens confined in banks with unconfined queens from established colonies. We also introduced banked queens into new colonies at the end of the almond bloom, and their performance was assessed throughout the year alongside Hawaiian-sourced queens (March 2021 – January 2022).

We gathered feedback from producers when we presented preliminary results at several industry conferences in 2021 and 2022. Taking advice from these producers, we followed a stringent protocol for selecting bank colonies and overwintered queens in bank colonies with two different stocking rates in Western Oregon (October 2021 – January 2022 and October 2022 – January 2023). We refined our protocol in response to our survival results from banks overwintered in 2021 – 2022 and 2022 – 2023. We also described our protocol in a newly published technical guide on queen banking.

Our goal was to evaluate the technique of overwintering queens in bank colonies for beekeepers in Oregon. We posed some research questions regarding this technique: will overwintering queens in bank colonies for approximately 4-5 months effect their reproductive potential? How will these queens perform compared to the standard Hawaiian-sourced queens? What is the optimal positioning for queens inside bank colonies to maximize winter survival? We will continue evaluating this technique next winter. The following is the progress pertaining to the study:

Year 1

1. We determined the percent survival rate of queens overwintered in bank colonies (n=20 queens per bank) with three commercial beekeeping operations in Oregon (September 2020 - January 2021).
2. We sampled queens that overwintered in two situations: a) confined in bank colonies and b) unconfined in established colonies (January 2021). We analyzed these queens for morphology, total sperm count, and sperm viability.
3. We introduced queens that overwintered in bank colonies into newly established colonies after the almond bloom in California (March 2021). We evaluated the performance of these queens throughout the year alongside Hawaiian-sourced queens (March 2021-January 2022). Performance metrics include colony acceptance, queen longevity, colony strength, brood pattern quality, and brood disease prevalence.

Year 2

1. We determined the percent survival rate of queens overwintered in bank colonies of two different stocking rates (n=30 and n=60 queens per bank) in Western Oregon (October 2021 – January 2022).
2. We will analyzed queens that overwintered in bank colonies of two different stocking rates for morphological traits, total sperm count, and sperm viability (February 2022).

Year 3

1. We determined the percent survival rate of queens overwintered in bank colonies of two different stocking rates (n=30 and n=60 queens per bank) in Western Oregon (October 2022 – February 2023) with a modified positioning strategy for the queen banks stocked with 60 queens.
2. We published a technical guide on queen banking that extensively covers this technique. The guide is free to download (see Information Products section).