The popularity of indoor storage is rapidly growing among US commercial beekeepers. As recently as the last 2-3 years, more beekeepers have adopted indoor storage as an overwintering strategy. Exactly how many beekeepers are now using this method, however, remains unknown. No widespread survey has been conducted on the number of beekeepers and colonies involved in indoor storage. This is information is valuable, as long-term trends in management practice popularity and their associated levels of winter loss can help inform management recommendations.

This year, the Hopkins Lab partnered with Gregory Shved of Exchange Bees LLC. Together, we devised a preliminary set of questions for beekeepers to help inform current trends in indoor storage. While the sample size of this initial effort is small (26 beekeepers), it represents more than 500,000 colonies from the top states that ship colonies to almond pollination (Figure 1), We believe this initial assessment of the demographics of indoor storage is interesting, and look forward to expanding the survey to include more beekeepers in future years. 

Figure 1. Top states that ship colonies to California for almond pollination. Source: Apiary Shipments through California Border Protection Stations, CDFA Plant Health and Pest Prevention Services.

The overarching goals of this effort are to understand how many colonies are being stored, where they are being stored, and where is there a demand for indoor storage that is not being met. Future questions to ask include the risks and benefits of indoor storage, as well as associated levels of winter mortality compared to outdoor wintering locations. Preliminary demographics are presented below.

Figure 2. Number and percentage of beekeepers and colonies in indoor storage in each state.

This initial effort summarizes the indoor wintering demographics of 26 beekeepers who store colonies in 6 US states (Idaho, North Dakota, Washington, California, Montana, and Utah). Altogether, they store 545,000 colonies indoors overwinter. The state with the most beekeepers storing colonies overwinter was Idaho (14 beekeepers, 53.8%). Idaho also had the most colonies stored overwinter (419,000 colonies, 76.9%). North Dakota was the second most popular state for indoor storage, followed by Washington, California, Montana, and Utah, respectively. The demographics of these states are summarized in Figure 2.

We also asked beekeepers whether they stored colonies in buildings that they owned, or if they rented storage space. The majority of beekeepers owned their own storage space (Figure 3; n = 18, 78.3%), but some beekeepers also reported renting space (n = 5, 21.7%). Of the five beekeepers who rent storage space, they reported rental prices ranging from $8-12 per colony.

We were also interested in the method of cooling each storage space utilized. Almost two thirds of beekeepers reported that their colonies were cooled by refrigeration (Figure 4, n = 12, 63.2%), while one third reported their storage spaces used evaporative cooling (n = 7, 36.8%). While there is no old survey data to reflect upon, evaporative cooling or the use of fans to bring cold air in from outside the building was the norm in the past. It is clear from this survey data that refrigeration is the dominate method of maintaining temperature. Evaporative cooling is sufficient for potato and onion storage where the contents do not produce much heat, and the use of these facilities was dominant before beekeepers began building facilities for the specific purpose of storing honey bee colonies.
 
In contrast, thousands of bees produce large amounts of heat that must be dissipated and controlled, so with the design and construction of new facilities most have moved to refrigeration for cooling demands and tighter control of temperatures. The use of refrigeration has other benefits including the ability to move bees in earlier in the season and the ability to utilize the cool space at times other than winter.

We plan on expanding this survey to collect more information on the demographics of indoor storage in the coming months and years. You can look for regular updates as we have them on the new online home of the storage guide at: ProjectApism.org/Indoor-Storage-of-Honey-Bees

Figure 3. Number and percentage of beekeepers who reported renting or owing indoor storage space.

Figure 4. Number and percentage of beekeepers who reported using evaporative cooling or refrigeration in indoor storage.

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