Click Here if you listened. We’d love to know what you think. There is even a spot for feedback! Read along below!
Are Your Bees Winterized?
By: Jay Evans, USDA Beltsville Bee Lab
If you are in the colder half of the northern hemisphere, brood production in your colonies has slowed or stopped by now. Besides occasionally checking in on their pantries, you have only to wait patiently and hope that they, and you, did what needed to be done to hold the line against an inevitable decline in worker bee population.
What did both parties do to take some of the drama out of the next few months? As beekeepers you have a few options, besides decent nutrition, to decrease the giant sucking sound of Winter bee mortality. Darcy Gray and colleagues at Pennsylvania State University have added excellent new arguments to the role beekeepers play in keeping more colony members and colonies alive through the cold months. In “Effective pest management approaches can mitigate honey bee (Apis mellifera) colony Winter loss across a range of weather conditions in small-scale, stationary apiaries” (Journal of Insect Science, (2024) 24(3): 15; ieae043 https://doi.org/10.1093/jisesa/ieae043) they underscore how important it was for you to get a handle on parasitic mites in your colonies last Summer. In this study, rather than experimentally test methods (although they do cite prior evidence mounted via experiments), the authors surveyed 3000 Pennsylvania beekeepers for their management styles and checked in on their success in keeping colonies alive across multiple years. Using the intriguingly named “Random Forest Models”, they sought the trees that were most important in a forest of impossibly complex factors that drive colony success or failure. These models “are strong in characterizing nonlinear relationships with many correlated predictor variables” and beekeepers are well aware that the good and bad factors in a bee colony’s life are both intertwined and complicated (i.e., ‘nonlinear’).
What they found was both consistent with prior efforts and novel in offering some new subtleties. Their ‘study population’ comprised bees and their keepers in a four-season state, Pennsylvania. They specifically targeted beekeepers who don’t hit the road with their colonies, a majority demographic for readers of Bee Culture and U.S. beekeepers overall. The key message, and not a huge surprise, is that beekeepers who treated for mites came back to more living colonies in the Spring. Interestingly, beekeepers who alternated across multiple mite treatments did even better, suggesting that a two-hit (or more) system is a good idea for many beekeepers. It was beyond the scope of this survey to identify the optimal two hits that have the best effect, nor did they weigh in on overall treatment intensity. In their words, “beekeepers in the single-treatment type group may have treated repeatedly or heavily, while those with multiple-treatment types may have applied treatment less often, or vice versa.” They DID gather data on the types of treatments used singly and multiply, showing that survival was bolstered significantly by both of the licensed organic acids, apivar (amitraz), and thymol, but especially when beekeepers used two or more of these four strategies. Interestingly, it mattered little in the end which of the four was used. Other management strategies, including the type of supplemental feeding beekeepers used, also had little effect on survival. Of the environmental components not under the whim of beekeepers, seasonal precipitation and growing degree days came out as important factors for survival for both categories of mite treatment, while on-the-ground estimates of forage seemed to rank higher for apiaries treated with just one miticide. What is striking is that colonies given a two-hit treatment regime did better across a wide range of weather and landscape challenges, again highlighting how important it is to keep mites down and the importance of hitting them with two or more active ingredients. This is consistent with the good management practices many of you teach and deploy currently.
If beekeepers have more evidence for what to do, how is the report card for your bees? Since a landmark paper by Heather Mattila, J. Lloyd Harris, and Gard Otis (“Timing of Production of Winter Bees in Honey Bee (Apis mellifera) Colonies” (2001) Insectes Sociaux 48 88–93, https://www.tandfonline.com/doi/abs/10.3896/IBRA.1.49.2.04) many scientists and beekeepers have been intrigued by the cues bees use to decide Winter is coming and the means they use to raise sisters who are just a bit better at hanging in there for unusually long lives. Building on excellent work in bee physiology (e.g., Huang, Z.-Y. and G.E. Robinson, “Seasonal changes in juvenile hormone titres and rates of biosynthesis in honey bees” (1995) J. Comp. Physiol. B 165: 18–28, https://link.springer.com/article/10.1007/bf00264682) Mattila and colleagues mapped out both physiological changes in bees and how those worked best in order to achieve healthy colony numbers in the Spring. This field got a boost this month from a new paper by Jelena Spremo and colleagues in Serbia (Spremo, J., Purać, J., Čelić, T., Đorđievski, S., Pihler, I., Kojić, D., & Vukašinović, E. “Assessment of oxidative status, detoxification capacity and immune responsiveness in honey bees with ageing” (2024) Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 298, 111735, doi:https://doi.org/10.1016/j.cbpa.2024.111735). They tackled the stresses we social organisms face while ageing in a crowded world; chemical stress, disease and just the general pressure of the environment on our fragile cells. Surprisingly, Winter bees did not show huge differences in the activity levels of genes whose proteins tackle chemical threats, when compared Summer bees. The strongest result came from two immune proteins that can generally suppress infection in bee bodies by interference or a form of ‘scabbing’. Winter bee abdomens showed higher activity for these genes versus Summer bees. The abdomen region is known to produce the primary immune responses for honey bees and it seems likely that Winter bees were poised from the start to have a better immune defense against whatever challenges came their way. This is not to say that they don’t differ at all from Summer bees, and ample studies have shown they do, just that as they build their armor for Winter, they have biological threats in mind along with chemical or environmental threats. Like humans, this immune defense decreased as bees grew older, but by stretching the limits they presumably kept a few more bacteria, gut parasites, or viruses at bay during their many months of life.
These studies help to divide the pie of tasks needed by beekeepers and bees to get through a long Winter. If you do your part, your bees will do theirs, and they should live to see more flowers soon enough.
