Using Cold Storage For a Brood Break in One of the Hottest Places on Earth

By: Dr. Kelly Kulhanek and Dr. Brandon Hopkins

Photo: Desert scenery of the Picacho State Recreation Area in Imperial County, California. (Adobe Stock Images)

In the Imperial Valley of Southern California, the average high temperature in July is 107°F. This region of desert stretches south from the Salton Sea all the way down to Mexico. The highest temperature every recorded in the Valley was 121°F, only 13 degrees shy of the world record recorded in nearby Death Valley, CA. Despite these conditions, the Valley is home to several commercial beekeepers keeping thousands of colonies in the Valley during summer. One family, the Ashurst’s, has dominated beekeeping in the area for generations. The Valley’s winters are mild which provides good conditions for wintering colonies outdoors. The summers, however, are tough and require special considerations for bees. Some of these methods are relatively simple, like providing shade for every apiary. More recently, novel use of cold storage facilities have offered both bees and workers a respite from the heat. We spoke with Bryan Ashurst of Ashurst Bee Company about how he uses his cold storage facility in July and August to help his bees beat the heat.

Figure 1. A typical Ashurst Bee Company apiary located in the Imperial Valley, CA. All colonies are provided shade to help combat high summer temperatures.

Brood breaks are becoming an increasingly popular practice in beekeeping, typically with the goal of reducing Varroa populations. Varroa reproduce inside capped brood cells, meaning that the majority of a colony’s Varroa population typically exists under capped brood. Inside brood cells, mites are protected from many chemical treatment options. The idea behind a brood break is that the queen is prevented from laying so that all existing brood will hatch, forcing the mites into the phoretic phase where they are much more susceptible to chemical treatments. Traditionally, the queen is prevented from laying by placing her in a cage. This method is labor intensive, as the queen must be manually located in each colony. The amount of labor required for this method typically means it does not fit into the workflow of a commercial operation. Cold storage offers an opportunity for commercial beekeepers to create a brood break in their colonies with far less labor invested.

Cold storage facilities are typically held between 45-55°F, and are kept completely dark. These conditions mimic winter, and cause colonies to go into periods of dormancy where the queens stop laying and the colonies become broodless. This broodless period combined with an application of a chemical Varroa treatment can yield excellent mite control and improve colony health long term. Inducing a brood break using cold storage may be particularly helpful in warm climates, like the Imperial Valley, where colonies would not normally ever become totally broodless. Bryan Ashurst has been using his cold storage facility to perform a brood break on his operation for the past few years, the practice quickly becoming a permanent part of his summer management.

Bryan described his typical schedule for us: the year begins, as for most commercial beekeepers, with shipping colonies to almond pollination. After almonds, the hives return to the Imperial Valley where they are shook to make singles (this is also done with the help of the cold storage facility, stay tuned for another blog on this practice). The hives are then placed out in apiaries where they begin making honey for the spring and early summer. By late July, most of the bees will have wrapped up their honey crop and are now ready to be treated for Varroa. Bryan begins bringing in colonies about 900 at a time; eventually holding about 3000 at any one time. This is the magic number that his facility can handle while working against the over 100°F outdoor temperatures. Only the overwintered (parent) colonies go into the cold room, Bryan leaves his new splits out.  Generally, the parents have more mites and other issues compared to newly made colonies.

Once the hives reach the cold storage facility, they are first subject to an inspection; they get checked for queens, have supers pulled, and are assessed for overall strength. All colonies also receive a Varroa treatment at this time. This is all done in a screened room with fans that is shaded and cooler than outside but not actually refrigerated. The major benefit of doing this step in the screened room verses outside in the apiaries is that Bryan’s crew can work safely and comfortably during regular work hours. This cuts back on drive time for the crews.  Bees come to them rather than sending crews out in all direction to the yards, and they are able to work in an efficient assembly line at the cold storage facility . At this inspection, any colonies that are deemed too weak will be sent back into the field to receive extra attention. Colonies that look healthy will be placed into a refrigerated room to have their brood break. Once under refrigeration, the hives are left completely undisturbed for three weeks.

After their three week respite from the heat, the bees are brought back out of the cold room. They are left to sit for a couple of days to reacclimate to being outdoors, then they receive another Varroa treatment and are fed. One of the major considerations for placing colonies into a cold room during summer is honey consumption. Summer colonies have large populations of both adult bees and brood that all consume honey during the brood break period, meaning colonies need to be well fed. Bryan feeds his colonies sugar syrup before they enter storage, and then feeds them again a couple days after they come out. He does not feed pollen during this process as the bees tend not to eat it, and it can break up the cluster. With adequate hive weight and sugar syrup, Bryan has not had any issues with bees running out of food during the brood break.

Bryan likes this method for controlling mites post honey production, but he says there are longer term benefits as well:

His records show that colonies that get the brood break are on average 2-3 frames larger in almond pollination, and about 95% of them are in double deeps (and 5% in singles) in almonds compared to only about 50% of hives that got no brood break. 

Bryan also notices that the bees that come out of cold storage seem to forage more ferociously, seemingly because they got a taste of winter and are now in the mode to prepare for it.

One of the biggest benefits of the brood break in the cold room is that weak/diseased colonies don’t survive it. ​“The cold room doesn’t solve your problems, but it sure does expose them,” Bryan told us. Hives that were weak for one reason or another will effectively be killed by the cold room, but these are the same colonies that Bryan would normally find dead later in the year. This ends up saving Bryan time and money, because the colonies die sooner, before he invests time and money trying to nurse them along. Placing colonies into cold storage in summer might not be a great fit for every operation, but with Bryan’s circumstances and the care he takes before and after hives go into the cold room, the brood break seems to be a huge benefit to his operation, and he plans to keep using this practice for the foreseeable future.

Learn More about indoor storage of honey bees:

Project Apis m.'s Indoor Storage Resource Page

Guide to Indoor Storage of Honey Bee Colonies in the USA

Hopkins Honey Bee Lab At Washington State University