Véto-pharma Phil Craft, our technical advisor in the U.S.A., is the former Kentucky State Apiarist, and an occasional contributor to Bee Culture magazine. We asked him to share 5 tips with you for better over-wintering of your colonies.
Winter can be tough on bees. With cooler weather and a lack of nectar and pollen resources, honey bees face a challenging period of the year. While bees have been meeting this challenge for eons, our role as beekeepers is to assist them in order to improve survival rates and colony health. In this article, I will pose five questions you should be asking yourself in the early autumn to make sure that your colonies are ready for the upcoming change of season.
A colony cannot properly prepare for winter without a queen present and laying eggs in the fall. Bees that emerge in the fall are crucial for the colony’s winter survival. These young “fall bees” are the ones that will beat the workers six-week life expectancy, and be there to start the colony’s build up in the spring. Do not worry about seeing the queen. The presence of eggs or even of young larvae is sufficient. It tells us that the queen was there and laying very recently, and that is good enough. Seeing all stages of brood (eggs, larvae and pupae) is also an overall indication of colony health. Unhealthy colonies cannot easily rear lots of new bees. This time of year, you want to see a lot of brood in your hives.
A colony should go into the winter with a minimum of about 25,000 bees (Langstroth hive). This is roughly a deep box with all frames covered with bees. At least this many bees are needed for efficient clustering during cold weather and for movement of the cluster to honey stores. Even in the best of circumstances, colonies will lose bees during the winter. Some will die of old age! A cluster that is too small at the beginning of the winter can lead to the loss of the colony by its end. It is better to combine two weak hives in the fall in order to create one stronger one than it is to risk losing both. While smaller populations can be wintered, this is tricky and requires balancing food stores, bee populations, and hive construction. My advice is, have AT LEAST a deep box full of bees. Higher numbers will be necessary in colder climates.
We know that bees which suffer from parasite or disease problems do not live as long as healthy bees. The greatest threat to the health of honey bees comes, as it has for the last several decades, from varroa mites. In addition to the damage it inflicts directly, a heavy mite infestation may make it impossible for a colony to rear the brood it needs for winter survival, and can shorten the life span of adult bees. Mites are also vectors for viruses which adversely affect the colony’s health.
The first question I ask beekeepers who contact me after losing colonies in the winter is, “Did you monitor or treat for varroa?” Too many times the answers are “no” and “no”. I do not advocate automatic preventative treatments; the best practice is to monitor and treat as needed. Never-the-less, most winter losses are related to mites. For beekeepers – especially new beekeepers – who have not been monitoring, preventative treatments are probably preferable to none. Some people find the process of monitoring intimidating or cumbersome, but that shouldn’t be a deterrent. Devices like the Varroa EasyCheck are available to make it simpler. If you are uncomfortable with an alcohol wash (which kills the bees in the sample), a sugar roll is a less lethal though less accurate alternative.
When treating is necessary, please use a product specifically designed for honey bees. You do not want extra inactive ingredients which may have damaging effects on your colonies. If, after your fall varroa treatment, monitoring reveals that your mite infestation is not as low as expected, you can use oxalic acid during winter (around November or December) to lower the infestation before the spring build-up. Vaporized oxalic acid administered during this period can be an excellent winter mop-up treatment to knock varroa levels back down.
With the exception of those in the far north, most beekeepers do not find it necessary to insulate their hives during cold weather. And even there, most wrap rather than insulate. The only physical modification I recommend for beekeepers in most regions is the installation of mouse guards. A warm, dry hive can be an enticing refuge for mice. Beekeepers who fail to take precautions (and I admit to being one of them from time to time) may find nests, damage to comb, and sometimes mice themselves in their hives come spring. Mouse guards, or entrance reducers as they are also called, often consist of solid blocks of wood which fit in the hive entrance and restrict it to an opening that a mouse cannot get its head through, which means the mice cannot get in! Unfortunately, some beekeepers have the mistaken impression that the purpose of entrance reducers is to help keep the hive warm by restricting reducing drafts of cold air. In fact, good ventilation is just as important in winter as it is in summer. That’s why I prefer (when I do get around to it) to use mouse guards made of perforated metal strips which effectively block mice, but do not impede the flow of air. A colony is capable of dealing with cold temperatures, but is stressed by the cold, wet conditions created in a poorly ventilated hive.
Though honey bees are cold blooded animals and therefore not individually capable of thermoregulation (meaning that they cannot control their own body temperature), collectively, they use an impressive array of strategies to regulate temperature within the hive. In summer, they deposit droplets of water throughout and fan them with their wings. As the drops evaporate, the change of state produces a reduction in temperature much as evaporating beads of sweat cool our skin in hot weather. At the approach of cold weather, the bees caulk unwanted cracks and openings in the hive (whether it be a brood box or a hollow tree) with propolis produced from resin and other plant material. Every beekeeper who has ever used a hive tool to pry two boxes apart knows what an effective sealant propolis makes. The key to winter warmth, however, is the cluster. When the interior temperature reaches the mid 60’s, the bees have already formed a loose ball to share body warmth. The cluster shrinks as it becomes colder and the colony huddles closer. Meanwhile, some individuals flex their thoracic muscles to produce heat in an action that resembles flying in place. By the time a thermometer placed in the hive would read in the mid 50’s, the cluster consists of a compact shell of stationary, flexing bees and an inner core where individuals can move about on the comb and feed. The shell can be several layers thick, made up of bees with their heads facing inward. Workers change positions, rotating between the shell and the core, but the queen stays always in the sheltered center. In this way, by muscle contractions, by expanding and contracting the cluster, and by increasing or reducing the number of bees in the shell, the colony can maintain a temperature of about 68°F within the cluster even when it’s well below freezing outside. Pretty amazing! But heat isn’t all they produce. Bees also breathe, and produce moisture that needs an outlet. There’s an analogy I like to use. The local university where I live plays basketball in a huge arena, which can hold more than 24,000 people on game nights. A couple of years ago, there was an article in the local paper which said that it has to get close to 40° F outside before they turn on the heat. All those bodies, packed tightly together generate plenty of warmth. However, the arena has to run ventilation fans to disperse the humidity from all that perspiring and respiring humanity. It’s very much like a winter cluster, except the bees do it more efficiently, and they don’t need a clear line of sight to watch the game. Though they don’t perspire, but they do breathe, and respiration gives off moisture.
Honey bees are very capable of heating the inside of a hive in the winter, even at extremely cold temperatures. New beekeepers who live up in northern climates are especially quick to worry about the cold, and their impulse is to seal all the gaps and holes in their hives, just as they do in their homes, to eliminate drafts. Isn’t duct tape great stuff? Yes, we don’t want our bees to be cold, but we also don’t want them spending the winter in a damp hive. How warm do you feel wearing a wet wool sweater? If a hive is too well sealed, moisture is trapped inside. You see the evidence of that in the condensation on your inner cover. I suppose people tend not to think of humidity as a winter issue because conventional heating systems in our homes have the opposite effect. They dry the air to the point that we sometimes have to use humidifiers in order to be more comfortable.
If you’re not sure whether the area you live in is cold enough to require special modifications, ask your neighboring beekeepers what do to winterize. If they wrap, you might want to follow their example. Special hive wrapping materials can be purchased from beekeeping suppliers, however don’t forget about ventilation. Even wrapped hives, in very cold climates – think Fargo, North Dakota – need ventilation. Pay attention to the ventilation directions that come with the hive wrapping material. Some hobby beekeepers (I do not know any commercial beekeepers doing this) have found it helpful to invest in polystyrene hives. For most, mouse guards and adequate ventilation will do the job.
Bees need enough food stores in the fall to last through winter. In moderate climates approximately 55 pounds of honey per hive (25kg) should be sufficient; further north as much as 125 pounds (60kg) may be required. In order to gauge the amount in a hive, here are some approximate capacities of FULL frames of stored honey (sugar syrup is pretty much the same):
*European readers, and those using non-Langstroth hives. U.S. deep frame dimensions are 9.8 inches (25 cm) x 17 inches (43 cm), shallow frames 4.5 inches (11.4 cm) x 17 inches (43 cm), and boxes normally contain 10 frames. In Europe there are several different box configurations (Dadant, British National, Layens hives, etc.) with different size frames. You can interpolate my frame dimensions, and stored honey needs, or consult with nearby beekeepers, bee inspectors, or veterinarians, for the amount of winter stored honey needed in your area. Stored honey needs will always depend on the severity of winter in your area.
Of course, most frames will contain some combination of food stores and brood. Another way to get at it is to lift up on the brood boxes. With experience, you can estimate the weight of stored honey. But to really know whether a colony already has sufficient stores or is at least accumulating them, you MUST LOOK in your hives. In addition to honey, bees need pollen. Pollen is essential to brood rearing, so while watching honey reserves, also keep an eye on stored pollen and pollen being brought into the hive. There are a number of protein supplements which can be used to augment natural pollen sources. These can be purchased as patties (placed on the top of the hive), or in the form of a powder, which can be made into patties or even fed dry. Bees will store some of the powder as well as using some immediately.
The time to feed with sugar syrup and pollen substitutes, if necessary, is in the fall. Any winter feeding should be considered EMERGENCY feeding, as in, “I think the bees will starve if I don’t do something.” In climates where you can expect occasional daytime temperatures of 50° F (10° C) or more during the winter, it may be possible to feed syrup. In locations where it does not get that warm, bees will not leave the cluster to seek food in a feeder, so winter feeding with liquid syrup is of limited value. Top feeders work best in cold weather, because they put the syrup closer to the cluster. The down side of using syrup is the introduction of additional moisture into the hive – always a consideration, but especially so in winter. To minimize this problem, use only as much syrup in the feeders as the bees can take in during a brief warm spell, and make it thick (2 parts sugar to one part water.)
If you think your bees are in danger of starvation and you have no alternative to winter feeding, a superior method to consider is fondant, also referred to as bee candy. Placed over the inner cover or directly on top of the brood frames with a spacer or empty honey super to contain the candy, it is more accessible to the bees and avoids the moisture problem. Bee candy is cooked on the stovetop and is not complicated to make. Recipes are readily available on the internet. The candy can be broken up and pieces placed over the inner cover of the brood box, or placed inside a top feeder. To make it easier to reach, an empty honey super can be put on top of the brood chamber and the candy placed on stick supports on the brood top bars. Some beekeepers even make special fondant feeders, similar to inner covers but deeper (about 1 inch inside), and designed to suspend the candy over the brood frames. The candy can be poured into this feeder and placed over the brood box upside down.
As a last resort, a very old and very simple winter feeding method is to place dry granulated sugar on the inner cover. This is clearly a desperate measure, but beekeepers have told me that using it has saved hives from what they thought was certain winter starvation. Be aware that most hive losses from starvation actually occur in late winter or even early spring as the hive starts to rear brood and runs out of food stores. Keep an eye on your hives and their food stores as spring approaches.
Winter losses can be pretty high some years whether you live in the U.S.A., Canada, or France. By asking yourself these basic questions and preparing in the fall you can minimize them. I hope the information here helps you lower your losses, maintain strong hives, and have healthy bees ready for the new upcoming season!
Phil
by Véto-pharma 
by Juan Molina 
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