Final report for FNE23-050
Project Information
With this project, we evaluated the benefits of overwintering honey bee colonies of two different sizes in climate controlled storage in Pennsylvania and compared this to colonies overwintered outdoors. We compared survival and food consumption of a) nucleus colonies vs full size colonies inside cold storage and b) full size colonies in cold storage vs outdoors. We also measured the impact of fall varroa mite levels on survival and measured the effects of wintering location on spring colony strength. We determined that nucleus colonies did not overwinter well in the storage units. Full-size colonies survived equally indoors and outdoors, consumed the same amount of food, and were both negatively impacted by high varroa mite levels in the fall. Overall the expense of the units did not bring a benefit to the beekeeper. Further research is needed to determine whether this technology is useful for beekeepers in this region.
We sought to evaluate the benefits of overwintering honey bee colonies of two different sizes in climate controlled storage at four locations in Pennsylvania and compared this to colonies overwintered outdoors at each location.
We compared:
- Survival: a) nucleus colonies vs full size colonies inside cold storage. b) full size colonies in cold storage vs outdoor colonies.
- Feed consumption a) nucleus colonies vs full size colonies inside cold storage. b) full size colonies in cold storage vs outdoor colonies.
- Parasitic Varroa mite levels: Impact of fall varroa mite levels on survival
- Spring Colony Strength: Full-size colonies overwintered indoors vs outdoors
- Economics: a) costs of overwintering indoors and outdoors. b) feasibility and profitability of overwintering nucleus colonies in cold storage.
Beekeepers in Pennsylvania are facing overwintering colony losses of 40% or more each year. These losses are commonly attributed to colony starvation, the parasitic varroa mite, and weather. New practices are needed to improve sustainability and profitability of beekeeping. Climate controlled storage of honey bees is a known and established practice in Canada, Minnesota and other regions that experience extreme low winter temperatures, but is increasingly being used in warmer climates, such as Texas, to improve health and profitability in beekeeping. Climate controlled storage of honey bees has rarely been recorded in Pennsylvania. We propose to study the benefits of climate controlled storage in four locations in Pennsylvania to determine if the practice is economically viable and beneficial to farmers in this region by reducing colony losses, food consumption, pest infestations, and energy inputs.
Honey bees forage on nectar from flowering plants to create honey which serves as their source of energy during the times of year when floral resources are not available. Honey bees do not hibernate, they regulate the temperature of their nest during winter by forming a cluster and vibrating their wing muscles to create heat. Temperatures inside the cluster are maintained between 82 and 94°F. At low temperatures, below 30°F, the cluster contracts to conserve heat while consuming more resources to generate heat. At extremely low temperatures the cluster is so contracted that the bees may not be able to access the food stores within the hive, which increases the risk of starvation if food stores are out of reach inside the hive. At temperatures above 50°F, the cluster expands and the bees become increasingly active and leave the colony in an attempt to forage. Foraging is energetically costly for the colony, reduces the lifespan of the individual bees, and requires the beekeeper to provide additional supplemental food sources. The cluster operates most efficiently when ambient temperatures are slightly above freezing.
Floral resources in Pennsylvania become scarce in the fall and honey bee colonies rely on stores of honey collected earlier in the year or on supplemental food provided by the beekeeper. As our landscape and weather change, there are increasingly fewer floral resources, particularly later in the year, which results in costly supplemental feed to maintain colonies. For example, 350 colonies in PA, owned by Extract and Box, LLC, require over 4000 lbs in liquid syrup during the fall and 1200 lbs of dry sugar over winter to mitigate resource losses from vast temperature fluctuations. Additionally, when outside temperatures are warm and floral resources are scarce, honey bees and other insects will attempt to steal honey from other hives in a behavior known as robbing. Robbing is detrimental to the colony that is being robbed, as it loses its food stores, and the colony that is doing the robbing may bring diseases and pests back to their hive. By placing colonies indoors, robbing behavior cannot occur.
Varroa mite infestations are a leading cause for disease transmission and negatively impact colony survival. Varroa mites damage honey bees by feeding on the developing bees and transmitting/activating harmful viruses. Exposure to mites and viruses reduces lifespans of winter bees that increase colony mortality. Because varroa mites can only reproduce when the bees are rearing young, a pause in brood production is a pause in mite development. Placement of colonies indoors in constant darkness and constant low temperatures result in the queen ceasing to lay eggs and the colony will become broodless. This added benefit of halting mite reproduction will likely lead to healthier colonies in the spring.
Additionally, climate controlled storage may offer beekeepers the ability to affordably overwinter very small colonies called nucleus colonies or nucs. Each spring Pennsylvania beekeepers import tens of thousands nucs and packages of bees from southern states. Some beekeepers transport their nucs to the south to overwinter, this comes at a high cost in labor, transportation, and carbon emission. Increased nuc sales are of interest to both the producer of these colonies and to consumers who are increasingly seeking locally available sources of bees.
Climate controlled storage of honey bees may offer Northeastern beekeepers an opportunity to adapt to a changing climate, reduce colony losses, decrease expenses, and increase profitability by overwintering small colonies which can be sold or used by the farmer the following spring. Understanding the benefits of this system and communicating the results of this research will empower farmers to make informed decisions to improve the sustainability and health of their bees while increasing profitability.
Cooperators
- (Researcher)
- (Researcher)
- - Technical Advisor
Research
In order to explore the benefits of climate controlled storage of honey bees we leased four specially designed climate controlled storage units from HiveTech Solutions (https://www.hivetechsolutions.com/mica) and placed them at four farms in Pennsylvania. A total of 343 colonies of honey bees, were dedicated to this project. 147 of the colonies were configured in standard single deep hives or “singles” (8-10 frames each) and 196 were configured in single nucleus hives or “nucs” (5 frames each).
During the spring and summer of 2023, each beekeeping operation prepared for the experiment by ensuring that honey bee colonies were strong, healthy, and the needed hive equipment was in working order. In August, the colonies for the experiment were chosen and a standard protocol for preparation wwas provided all participants. Parasitic mites were controlled using chemical miticides. During the months of September and October the colonies were fed supplemental sugar syrup, as needed, to reach the weight necessary for overwintering. In November, the nucleau colonies and half of the full-size colonies (singles) were placed inside the unit. The other half of the singles were placed just outside of the storage unit and monitored through the winter.
We compared survival of colonies by noting the number of colonies that went into the winter and the number of colonies that come out of winter alive.
We measured food consumption of colonies by giving each hive a unique identifier. The weight of the hive was measured in November just prior to to entering the cold storage unit (or placement next to it). Hives were weighed again within one week of removal from the cold storage unit in March.
Adult bee populations were assessed by visualizing the bees on each frame. The area of bees will be estimated as the number of frames covered with bees for all colonies in November and in March.
Levels of parasitic varroa mites were assessed using a standard procedure. From each colony, ½ cup (300 individuals) of bees is collected into a pint glass jar containing alcohol. The jar was shaken for one minute to dislodge the mites from the bees. The alcohol was poured through a fine sieve to catch the mites, which were counted. The number of mites per 100 bees was then determined. This procedure was conducted for all colonies in November and March.
Our Data was consistently logged and monitored using a dashboard provided by HiveTech. This live dashboard allowed each principal to see his or her current and historical data. Temperature, inside and outside, relative humidity inside and outside and internal CO2 levels were constantly monitored and recorded.
The data were used to estimate the cost of overwintering indoors and outdoors and the profitability of overwintering nucleus indoors compared to indoor and outdoor overwintering of standard colonies. We used data from the economic inputs and survival to describe the profitability of each treatment type by using anova t-test.
Differences in results at the different sites were investigated.
There was no statistically significant difference between survival of nucs vs full-size colonies wintered indoors (P=0.13). In addition, There was no statistically significant difference between survival of full-size colonies wintered indoors versus outdoor (P=0.77). Generally, survival of colonies that were wintered indoors was poor and no difference from the survival of colonies kept outdoors.
Survival of nucleus colonies, all of which were overwintered within the cold storage units, was generally poor, ranging from 6% to 61%. This result was devastating for the beekeepers involved. We do not recommend attempting to overwinter nucleus colonies in cold storage.
Despite the distribution of a protocol to all participating beekeepers who were preparing bees for overwintering, there were differences in practices. Importantly, the sugar syrup that was used to get the bees up to their target weight varied. While one beekeeper used commercial invert syrup that is 4:1 sugar:water, others used sucrose syrup with a ratio of 2:1 sugar:water. In addition, the timing of this feeding varied, with some beekeepers feeding up until 2 weeks prior to moving into the unit and others completing feeding much earlier. Thus, the bees that were fed both the 2:1 syrup and fed late were not given ample time to ripen the feed. Feeding on too much water while not having the ability to defecate while wintering indoors combined to cause great mortality. Upon opening the units, beekeepers reported seeing vast amounts of dysentery and mold. These surely impacted survival within the unit.
There was no statistically significant difference between the amount of food, by weight, consumed (colonies that survived) by nucleus versus full-size colonies that were wintered in the cold storage unit (P=0.14). In addition, there was no statistically significant difference between food consumption of (colonies that survived only) full-size colonies that were wintered inside or outside of the cold storage unit (P=0.65). Based on previous research that was shared with us, we expected the colonies kept in cold storage to consume significantly less stored food than those overwintered outdoors. The calm, stable environment was expected to allow the bees to consume and use less energy. That was not the case in this experiment.
For nucs, fall mite levels marginally impacted overwintering survival (P=0.09). For full-size colonies, fall mite levels significantly impacted overwintering survival in colonies kept indoors (P=0.04) and outdoors (P=0.025). I has been shown time and time again that varroa mite levels in the fall impact overwintering survival of colonies. We showed this as well, especially for full-size colonies. Parasitic varroa mites harm bees by feeding on them and by transmitting and activating viruses. Thus, controlling mites prior to the stressful winter period is critical. Unfortunately, we did not measure virus levels, but we assume they correlate with mite levels and resulted in the differences we saw here. Beekeepers should take care to ensure that mite levels are as low as possible entering winter.
Spring bee population in full-size colonies was significantly impacted by where they were wintered (indoors vs outdoors) with outdoor-wintered colonies entering spring stronger than indoor-wintered colonies (P<0.0001).
Estimated energy consumption for the 5 months of indoor storage cost approximately $166.31 per unit. Because food consumption did not differ between indoor and outdoor wintered colonies, the costs of preparation did not differ. Energy, plus rental costs made wintering bees indoors more expensive than wintering outdoors.
Please see results figures in a slideshow format at https://docs.google.com/presentation/d/1X5ttB-DADBJVBlnoAZ2UDTmTVXuvgU8RLe9M-Idqlb8/edit?usp=sharing
Wintering honey bee colonies in indoor temperature-controlled storage units was not a benefit to the beekeepers in this study. Survival was not improved, while costs increased for colonies that were kept in the storage units. In particular, survival of nucleus colonies, was generally poor and is not recommended. Thus, without further research showing a benefit of cold storage for honey bees over winter in PA, this new technology will not benefit beekeepers.
For future studies, it is recommended that bees are fed very thick sugar syrup in preparation for overwintering and that they are treated with fumagillin in the fall. These will likely increase survival and decrease the probability of dysentery. In addition, varroa mites must be under control prior to overwintering so that colonies can successfully survive.
We were disappointed by these results, but are moving forward with further studies based on what we learned. We still believe there is a place for cold storage of bees and beekeeping equipment in the northeastern US and hope to find financially-beneficial uses for the units. For now, however, this remains in the research phase and is not recommended for general use.
Education & Outreach Activities and Participation Summary
Participation Summary:
Talk given to Chester County Beekeepers Association members.
Talk given to beginning beekeepers through Extract and Box, LLC.
Website summary of results posted at https://extractandbox.com/climate-controlled-apiaries/
Newsletter article through PA State Beekeepers Association
Article in Lancaster Farming publication
Talk at summer picnic of the PA State Beekeepers Association
Talk at conference of the Manitoba (Canada) Beekeepers Association meeting
Learning Outcomes
Beekeepers are skeptical of this new technology. They are hesitant to add this to their operations without further research.
Project Outcomes
Unfortunately, we have not yet seen a benefit of this work. So far, we have not obtained data that shows that this technology will help beekeepers in PA or the northeast. We hope that the lessons we learned in the 23-24 winter will help us to have great success in the 24-25 winter. We are thankful for the second year of funding so we can continue this work.
During this study, we attempted to overwinter nucleus colonies in indoor cold storage units. We now fear that these units have populations of bees that are inherently too small for this process. In addition, because the bees were fed sugar syrup containing too much water and too late in the season, the bees developed dysentery. For future indoor storage work, we will use not only larger colonies, but also thicker syrup to try to improve survival and eliminate dysentery. We will also treat colonies with fumagillin to eliminate dysentery-causing organisms prior to moving the bees into the units.
We successfully answered the questions we set out to answer with this study, but were disappointed with those answers. Because beekeeping is personal, we feel that we can ask the questions again, using different protocols, and aim for more positive outcomes. We also feel that the storage units can be useful to beekeepers in other ways and aim to explore those.
The bee losses during this study were a great financial burden to the beekeepers involved. They lost their precious stock and were not compensated for those losses. In the future, grant proposal budgets should include compensation for those losses, when possible.
We feel that further work is needed to determine whether indoor cold storage is a benefit to beekeepers in the northeastern US. For now, we do not recommend investing in this technology. However, we hope beekeepers will stayed tuned for more results as we continue to study this.