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  • Writer's pictureTrevor Bawden

What the Data Says About Winter Losses in the US

Updated: Apr 10

Put on your thinking cap because we are about to dive into what the data says about winter losses in the US.

Wisconsin winter bees
The Wisconsin winter is the best genetic bottleneck for breeding bees to survive

It’s time to discuss “why did my bees die” again, so it must be winter. In Wisconsin, DATCP (Department of Agriculture, Trade and Consumer Protection) reported a 44% colony loss for 2023 (“Wisconsin DATCP Apiary Program News - January 2024”). Now compare that to the 10% loss that we saw here at Lloyd St Bees. These figures really help showcase the difference that good management along with good breeding makes. In this article we will discuss the main reasons beekeepers blame their winter losses on and what we are doing differently at Lloyd St Bees to combat these issues.

Beekeepers across the US Offered up their opinions...

According to the Bee Informed Partnership (Steinhauer et al., 2021), the top four reasons for colony loss received by beekeepers across the United States are:

1.      Varroa mites

2.      Queen situations

3.      Starvation

4. Weather

Varroa Mites

The varroa mite came to this country over thirty years ago and shows no sign of leaving.  Varroa mites feed on the fat bodies of the bees and in the process of the feeding, they spread viruses like deformed wing virus and many others (Ramsey et al.,2019). This disturbs the bee’s brain, gut, immunity/healing ability and reduces their lifespan. The

varroa mite
Varroa mites after an alcohol wash

overall result is the bee’s declined fitness to be able to survive the winter for northern beekeepers. Beekeepers have been trying to figure out how to combat this issue for decades using various miticides for better or worse. Research points to one thing, bees that express the VSH (varroa sensitive hygiene) trait survive winter at higher numbers (O’Shea-Wheller et al., 2022). Here at Lloyd St Bees we have been selecting colonies for VSH using Dr. Harbo’s VSH assay (Harbo, 2020) for years now to help reduce our mite loads in our colonies. This has allowed us to have 75% of our colonies on average go into winter untreated all season. We still advocate for good management practices like testing your bees via the alcohol wash and treating them with some form of miticide on a case by case basis. We consider this good informed management because you can’t treat what you don’t know.

Research points to one thing, bees that express the VSH (varroa sensitive hygiene) trait survive winter at higher numbers (O’Shea-Wheller et al., 2022)

Queen situations

The BIP data says that 89%+ of sideline/commercial beekeepers are using new queens every season and 50% of backyard beekeepers replace queens every year. So why isn’t this working? We would like to propose the question, what are we replacing these queens with? Maybe it’s not just about replacement but more about the breeding,

Lloyd St Bees VSH breeder queen
A fat and sassy LSB breeder queen

quality, and safe transportation of the queens. Research shows that queens can be easily damaged due to heat/cold stress in as little as one hour (McAfee et al., 2020), that queen physiology can predict queen quality (Tarpy et al.,2012), the reduced amount of time the queen is allowed to lay (Rhodes et al.,2003) and mated queen banking can endanger a queen’s performance (Woyke, 1988). By producing queens locally and being more selective on the quality of the queen, we can avoid queen situations. We do this at Lloyd St Bees by exclusively using virgin queens and doing four things:

  • Producing our own queens and performing a physiological assessment before placing the virgin queen in a mating nuc.

  • Marking the virgin queen before placing her in the mating nuc so we can confirm that what we put in is what we get out.

  • Allowing the queen to lay for a longer duration in the mating nucs and not using queen banks for mated queens.

  • Producing more drones than we will actually need during the season to produce open mated queens and artificially inseminated queens.

Starvation and Weather

We are combining these last two because they go hand in hand. Good nutrition, specifically protein and carbohydrates, helps produce healthy winter bee in the late summer and early fall (Brodschneider et al., 2010). If the cluster is too small or not provided with proper nutrition, how will they produce their long-lasting winter bees that will survive the cold days into spring here in Wisconsin? Colonies that consume more resources during the winter starve before they reach spring. Why is that? One reason is that brood rearing never shuts down or starts up out of sync with the local weather. Why? Because imported bees are living on a California or Georgia winter timeline and not our Wisconsin winter timeline. We also know that varroa mites only reproduce in the brood (Ramsey et al.,2019). That means that colonies that continue to produce brood during the winter are steadily increasing their varroa infestation level.

In our breeding program, we use the Wisconsin winter as an equalizer for stock selection. All our stock is fed equally, clusters equalized to a minimum size threshold and small hive cavity size is used to allow the winter weather to make the selection for us. We consider these winter survivors as proven. They are in tune with the appropriate spring build up and ramp down to be successful here in our Wisconsin climate. Remember that every time you import bees from a warmer climate, you are essentially reshuffling the genetic deck for beekeepers in your state. Those bees have not gone through this winter genetic bottleneck.

Imported bees are living on a California or Georgia winter timeline and not our Wisconsin winter timeline.


If you’re diagnosing a winter dead out, consider the four factors that we previously mentioned. When managing your bees this season, it's important to manage all four of these issues previously mentioned and not just focus on only one. We strongly recommend you support local beekeepers who provide stock that stays within your local climate. This will help make your beekeeping management experience more enjoyable during the coming season. If you’re interested in local bees, check out our shop.

References (you should read these, they are great!)

“Wisconsin DATCP Apiary Program News - January 2024.” Wisconsin Department of Agriculture, Trade and Consumer Protection, Department of Agriculture, Trade and Consumer Protection, 4 Jan. 2024, Accessed 6 Feb. 2024.


Steinhauer, Nathalie, et al. United States Honey Bee Colony Losses 2020-2021: Preliminary Results. 23 June 2021.


Ramsey, Samuel D., et al. “Varroa Destructor Feeds Primarily on Honey Bee Fat Body Tissuse and Not Hemolymph.” Proceedings of the National Academy of Sciences, vol. 116, no. 5, 29 Jan. 2019, pp. 1792–1801,,


Noël A, Le Conte Y, Mondet F. Varroa destructor: how does it harm Apis mellifera honey bees and what can be done about it? Emerg Top Life Sci. 2020 Jul 2;4(1):45-57. doi: 10.1042/ETLS20190125. PMID: 32537655; PMCID: PMC7326341.


O’Shea-Wheller, T.A., Rinkevich, F.D., Danka, R.G. et al. A derived honey bee stock confers resistance to Varroa destructor and associated viral transmission. Sci Rep 12, 4852 (2022).

Harbo, J. (2020). Measuring Varroa Sensitive Hygiene. Harbobeeco. Retrieved February 6, 2024, from

McAfee, A., Milone, J., Chapman, A. et al. Candidate stress biomarkers for queen failure diagnostics. BMC Genomics 21, 571 (2020).

Tarpy, David & Keller, Jennifer & Caren, Joel & Delaney, Deborah. (2012). Assessing the Mating ‘Health’ of Commercial Honey Bee Queens. Journal of economic entomology. 105. 20-5. 10.1603/EC11276.

Rhodes, J., SOMERVILLE, D., & Harden, S. (2003, October 8). Queen honey bee introduction and early survival – effects of queen age at introduction. Apidologie. Retrieved February 6, 2024, from

Woyke, Jerzy. (1988). 1987 Problems with Queen Banks. American Bee Journal. 128. 276-278.

Brodschneider, R., Crailsheim, K. Nutrition and health in honey bees. Apidologie 41, 278–294 (2010).

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