More beekeepers are using cold storage to induce brood breaks or ease the summer dearth
Beekeepers have been keeping colonies indoors to pass through the depths of winter for over a century. For example, discussions of “cellaring” colonies in the coldest months date back to 1902, when G.M. Doolittle, a beekeeper in New York, wrote about the topic in an early issue of this very magazine. “The temperature of the earth, at a depth of five or six feet, is very near the one being right for safe overwintering of bees where they must be confined for four or five months,” Doolittle wrote.
But the benefits of keeping colonies inside extend well beyond protecting bees from the winter elements. In collaboration with commercial beekeepers, Brandon Hopkins and Kelly Kulhanek — assistant professors of pollinator research and extension at Washington State University — and their colleagues have been researching methods and benefits of storing colonies indoors for short periods during the spring and summer.
They have been investigating this topic for eight years, and the potential economic benefits are compelling. “There can be steep costs up front to get started,” says Kulhanek, “mainly if you build your own facility. However, many beekeepers rent space in others’ facilities, making the upfront cost lower. The idea is to reduce the inputs required to keep the colonies alive compared to what they would need outdoors.”
For example, most miticides are more effective and require fewer treatments when there is no brood present in which the mites can take refuge. In Italy, Hopkins recalls seeing many beekeepers caging queens ahead of mite treatments to induce broodlessness and improve treatment outcomes. “Caging queens was never going to be possible on a commercial scale,” Hopkins says, “but if we could make the colonies broodless by placing them indoors for a period of time, we could get the same results. We might be able to put whole semi-trucks of bees indoors and have them come out broodless.”
On beekeeper request, Hopkins investigated this very idea using colonies that had recently come out of almond pollination. Hopkins says that some beekeepers head to Idaho after almonds, where there is normally a lag time between when hives arrive and when spring forage pops. Those beekeepers saw an opportunity to use this time to induce a brood break with cold storage and make sure they flatten the mite curve before the rest of the production season ramps up.
Slowing things down to get ahead
Hopkins and his team tested this idea by putting 48 colonies in cold storage (at 40-45 F, or 4.4-7.2 C) immediately after almond pollination, and compared their outcomes two months later with another group of colonies that were kept outdoors. About three weeks after the experiment began, all colonies received an oxalic acid drizzle; the rationale being that 18-21 days of cold storage, or about one brood cycle, is what it takes to achieve broodlessness, and therefore heighten the treatment’s efficacy.
Indeed, their results, which are not yet published, show that colonies stored indoors had average mite loads of < 1%, whereas the colonies under conventional management had mite loads higher than 3.5%. What’s more, the colonies that were placed in cold storage also didn’t suffer a long-term setback as a result of this lost brood cycle, possibly because with mite levels knocked back so well, it was easier for them to build brood back up when given the chance. Honey production two months later was also not affected.
Bees in storage during the spring and summer do consume a lot of food, at a rate of about one pound per day, or seven times more than what they would consume during the winter, but they also require less maintenance and travel time for apiary visits. And on top of being more effective, miticide applications are less laborious with colonies packed in close quarters. Hopkins stresses, though, that this strategy won’t necessarily work well for all operations.
“You would ideally sample and know if you had a mite issue as part of an integrated pest management strategy,” he says in a webinar on indoor storage organized by Project Apis m., the Almond Board of California, and Washington State University. “It’s pretty extreme to take your colonies into this cold, dark period when they’re trying to ramp up, but if you come out of almonds and your mite levels are too high, it might be an opportunity to try this.” The researchers also repeated this study using colonies coming out of apple pollination, and found limited benefits, possibly because they did not go into storage with sufficient food stores.
But this isn’t all that a cold room is useful for. “Beekeepers who own and operate their own refrigerated facilities are finding lots of innovative ways to utilize their space at times other than winter months to make their operations and workforce more efficient,” Hopkins says.
Take Buzz Landon, president of the California State Beekeepers Association. Landon is a commercial beekeeper who runs about 6,000 colonies in northern California, and built his indoor facility in 2019, initially for the purpose of overwintering. But inspired by Bryan Ashurst, a commercial beekeeper in southern California who was using his cold storage facility year-round, Landon began to use the building for other jobs.
“The construction was actually completed in March, so I used it first for making up mating nucs and five-frame nucs,” Landon explains. “We cool them down inside so there is less flying and less absconding when they’re taken out.”
Landon adds that in the spring, the weather can be unpredictable, and working inside cuts out extra steps like hauling equipment to and from the field. “Sometimes you can’t get out to the yards due to bad weather,” he says. “Nobody likes shaking bees inside, but it does let you stick to a schedule.”
That includes having shifts that are convenient for the workers, making it easier to adhere to state labor laws. And whereas getting trucks of bees ready for distribution would normally require working through the night, the cold room allows trailers to be loaded without worry about overheating. In his operation, Landon says, all of this means that the cold room is used mainly in the spring, set at 44-50 F (6.7-10 C) and then again in the fall when bees go in for the winter, set at 40 F (4.4 C).
If these benefits of cold storage at unlikely times of year aren’t enough, here’s one more. Around a million queens are produced each year in California for export to Canada and distribution among other states, but during the hot summer months there is a disconnect between queen supply and consumer demand. Cold storage of queen banks could offer a low-maintenance solution of storing queens until demand picks up again.
Queens could, of course, also be banked in conventional colonies outdoors, but they require intensive management and are difficult to maintain in the heat. They need constant inputs of brood, protein supplement, and adequate honey frames or syrup to get them through the summer dearth. Anna Webb, a then-master’s student, and Stephen Onayemi, a Ph.D. student, joined Hopkins and Kulhanek to investigate if they could use cold storage as a kind of “set and forget” method of queen banking.
“Temperatures in central California, where many queen breeders are, are extremely high in summer,” says Kulhanek, “and they often have a surplus of queens to bank between spring and when beekeepers want to requeen in fall. Indoor storage could provide a way to bank queens for that summer period that requires less labor and materials costs than outdoor banks.”
The team used an astounding 2,150 queens to test survival and performance of queens banked in cold storage and ….