This Guide is adapted from "Wintering Bees in Cold Climates: Fall Management, Preparing for Winter, How to be a Good Beekeeper in January, and Diagnosing Spring Colony Deadouts" by Christina Wahl, Ph.D., Linda Mizer, DVM, Ph.D., and Diana Sammataro, Ph.D.
Download the full guide, including a dichotomous key to diagnose why your bees died over the winter.
Keeping bees is an agricultural endeavor, thus, success as a beekeeper depends on understanding the local environment. This guide was written for beekeepers whose bees overwinter in cold climates, where the temperatures between November and March typically range between an average high of 35 degrees F (2 °C) and an average low of 18 degrees F (-8 °C). To care for colonies with a prolonged winter confinement period, you must learn how to recognize and promptly deal with colony health and queen problems during the summer and fall, with an eye to ensuring that colonies enter winter dormancy in the best possible condition.
Good fall management is critical to successful overwintering
This point cannot be overstated: Good fall management is critical to successful overwintering! Fall management begins prior to the end of the last nectar flow and falling temperatures that would preclude mite treatments and supplemental feeding. In Upstate New York, this will be in August. You must ensure that your colonies are healthy and that they are storing enough honey in advance of the winter. If you do not begin this work at the appropriate time, there will not be enough time to “turn around” a colony in trouble before the frost comes.
Mite control is paramount. In hives residing year-round where cold winters prevent bees from flying, the bee population peaks in July and bottoms out in December. Mite numbers rise and fall proportionally to bee numbers, however they are phase-shifted, meaning that mite numbers are rising in August as bee numbers are starting to decline (see Figure 1). This situation can lead to a very unfavorable ratio of mites to bees by the time the bees begin to cluster in late fall. To combat this, measure your mite levels in late July/early August and treat promptly. No time to count mites? If you have bees, you have mites, so plan to control mites even if you don’t have time to first count them in every hive. Professional beekeepers do not measure the mite levels in all of their hives, but they most certainly treat all of their hives for mites, and so should all beekeepers. Since mite numbers will be peaking after bee numbers begin to decline, starting in August, treating bees for the first time in September or October is already too late. Re-check mite levels in September and if the numbers are still high, treat a second time using a different miticide (such as oxalic acid dribble, suitable for late season/minimal brood treatment) before packing your hives for winter. The treatment you apply depends both on your personal preference, and on the manufacturer’s recommendations. A chart to help you narrow your options is shown in Figure 2.
|Chemical Treatment||Active Ingredient||Type||Method||Efficacy||Cost per colony||Treatment duration||Can you treat with supers on?||Time to wait after treatment ends before you can super|
|Apiguard®||Thymol||Essential Oil||Tray with gel sits on brood frames||74-95%||$3.30 - $6.80||28 days (2 times for 14 days each)||No||Can super immediately after treatment ends|
|Api Life Var®||Thymol, eucalyptus oil, menthol||Essential Oil||Tablets placed on the corners of the brood nest||70-90%||$4.48 – $7.12||21-30 days (3 times at 7-10 day intervals)||No||1 month|
|MiteAway Quick Strips®||Formic acid||Organic Acid||Pads placed on brood nest||61-98%||$4.40 – $7.25||7 days||Yes||Supers can be left on during treatment|
|Oxalic Acid||Oxalic acid dehydrate||Organic Acid||Dribble brood nest or vaporize entrance||82-99%||$0.25 – $0.37||10 minutes||No||2 weeks|
|Hop Guard II®||Hops beta acids||Organic Acid||Strips inserted in brood nest||75-99%||$3.33 – $3.80||28 days||Yes||Supers can be left on during treatment|
|Apivar®||Amitraz||Synthetic Chemical||Insert strips into brood nest||95%||$5.00 – $6.90||42-56 days||No||2 weeks|
The recommended mite threshold at which treatment is recommended, and the detailed use of different treatments, is beyond the scope of this guide. Consult a good online reference, such as this website, for the latest information.
Winter honey stores must be adequate by the end of the last nectar flow. In Upstate New York, honey is no longer collected after the first week or so of October, depending on seasonal temperature and the strength of the goldenrod flow. Bees need heat to evaporate water from nectar as they cure it into honey. They must store enough honey to get them through the winter BEFORE frost stops them from being able to cure nectar or sugar syrup. You must evaluate hive stores, starting in early September, and anticipate any need to supplement hives with feed before frost shuts down the season. You will not be able to count on feeding hives past the end of September (although in some years it is possible to feed bees well into November). A full size hive (two deep Langstroth boxes or equivalent) needs a minimum of 80 pounds of honey. A nuc should have no less than 50 pounds of honey. If you must feed them to achieve this weight, use cane sugar dissolved in water at a 2:1 ratio of sugar:water. This ratio diminishes the amount of evaporation necessary to cure the syrup and it saves the bees energy. Use of a higher ratio (3:1) is difficult to achieve and will result in crystallization of the sugar that will make it more difficult for the bees to collect and utilize. You may add some thyme leaves or a few drops of thyme oil to the feed in each hive, if you wish. Thyme is antibacterial and antifungal, and does not bother bees. Lemongrass oil is attractive to bees and a few drops may be used, however these essential oils are not necessary supplements.
Rarely, in some areas and in some years, the bees do not collect enough nectar to survive the winter. How much honey should you leave on your hives? The answer will depend on the weather and bees. With experience you will learn the optimal balance between “enough” and “too much” for your bees in your location.
Always err on the side of “too much”. It is better to welcome live bees in the spring sporting an extra box full of last season’s honey, than to open a hive full of bees that starved to death. A few beekeepers advocate allowing all bees to die in winter. They have calculated that the value of the honey is greater than the value of the bees, so they do not attempt to support their bees over the winter.
However, if you are like most beekeepers who would prefer their bees to survive, then a good “rule of thumb” is to configure your full-sized colonies with double deeps or a deep and two medium (Illinois) boxes. The total weight of bees, hive furniture, and honey in such a set-up is ideally about 160 pounds. The minimum amount of honey you should leave on your full-sized colony is equal to one full deep box, or about 90-100 pounds (this is the full weight of the box, frames, bees, and honey). If you are overwintering nucs, each nuc should have the equivalent of 8 deep frames full of honey. Nucs overwinter best if they are housed in proper nuc boxes, such as two stacked, five-framed brood boxes. Because bees have trouble moving laterally in the cold, but moving up (presumably following the heat of the colony) is easier for them, a small colony like a nuc will be better able to access their stores if the frames are arranged vertically. Be prepared to check your nucs in late February or early March, they may need additional feeding at that time. You can tell if your bees need feed by simply lifting the outer telescoping cover on a day when the temperatures reach 400F (50C). If you see bees at the hole in the inner cover, they are running out of food and you should feed them immediately with a supplement such as fondant or granular sugar (Figure 3). Make these inspections brief. Removing the outer cover for any length of time is stressful to the bees.
In summary, if there is not enough honey on the hives, you will have to supplement the bees with sugar syrup. This MUST be done in the fall when the bees are still active. Use a 2:1 mixture of sugar to water. Do not give 1:1 mixture in the fall, as the bees must work to evaporate moisture from the syrup and this becomes a harder job as the days and nights become cooler. Once clustering begins, it is too late to feed your bees liquid feed.
What affects winter survival of honeybee colonies?
Both extrinsic and intrinsic factors will impact the ability of a colony to survive the winter. The main extrinsic factor affecting survival is weather. Winters vary considerably...they may be wet and cold, dry and cold, wet and mild, dry and mild, windy, icy, etc. We cannot control or even reliably predict the weather, but we can optimize colony housing conditions and food stores. It is important to choose a suitable hive location, ensure that hive furniture is in good condition and properly ventilated, and leave adequate honey stores in the hive. All these things can be readily optimized by the beekeeper and must be done while temperatures during the day are still above 50°F(10°C) because opening colonies in the cold is at best stressful, and at worst, lethal.
When you choose a location for your beehives, make sure that they are not in a low spot where damp air may pool and where temperatures tend to be lower than the surroundings. Determine the direction of the prevailing wind and create a windbreak. This can be as simple as placing the hives along a tree line (Figure 4). Alternatively, you can erect a simple temporary windbreak of burlap, snow fencing, or straw
bales. In general, wind speed is reduced on the downwind side of the windbreak for a distance of up to 30 times the height of the windbreak. Within this zone, the density of the windbreak will affect the amount of wind reduction. The more solid the windbreak, the less wind passes through it. If the windbreak is too dense (for instance, a solid building) then low pressure develops on the downwind side, creating turbulence that reduces windbreak protection. A windbreak density of 40 to 60 percent provides the greatest protection downwind. If you plan to erect a permanent windbreak for your hives, seek additional guidance online.
Animal damage and vandalism are problems that you should be aware may exist and you should protect your hives. In the fall, mice start looking for nice warm places to spend the winter. They are able to crawl in through your lower hive entrances when the bees begin to cluster and are not “at the door” to drive away intruders. To prevent mice from destroying frames in your hives and eating your clustering bees, place mouse guards in your lower entrances. There are nice ones available commercially, or you can make your own very easily using hardware cloth. Cut it to fit the width of the hive entrance, and ensure that it is at least three times the height of the entrance. Fold it in half and push it into the entrance (Figure 5). Elevating your hives using a hive stand is also helpful (see Figure 4).
Other animals that can damage your hives during the winter are skunks and raccoons. These pests will chew the entrances, and raccoons are even capable
of prying up the outer cover. You can prevent this by tying the hive down to the hive stand. Consider using a quick-release strap that will make winter hive inspections more convenient.
To deter vandals there is not much you can do, except to signpost the area around your hives (and consider labeling hives using nailed-on signs, brands, making engravings, or by simply writing on them). Strapping down the hives may help, because most vandals do not wish to risk
being stung, so they are less likely to linger around a hive that is firmly strapped down. If you want to invest some serious money, there are tracking devices available that you can place inside your hive that may be of use if the hives are stolen.
Bears live in much of our area. They are chiefly a problem during the spring, summer, and fall when they are active. However, during a mild winter they may also be a threat to beehives.
Bears cannot be easily deterred from totally destroying your hives once they have found them, so if you know there are bears in your vicinity you must preemptively install electric fencing around your bee yard. Some beekeepers hang strips of bacon on the live electric fencing around their bee yards if they know bears are active in the area. Because the bear’s thick hair and hide protects most of the animal, its nose is almost the only part of its anatomy that can be painfully shocked by the fencing current. By encouraging the bear to sniff the fence and get a shock to the nose, a clear message gets across: Stay away!!
Your hive furniture should be tightly fitted together. Bees do not heat the hive, they only heat their cluster. Drafts can drain the heat out of the bee cluster and will kill the bees. If you have old brood boxes that are warped or display hive tool damage, such boxes will have gaps that can
potentially cause deadly drafts during bad weather. Even small cracks between hive boxes can allow a lot of air to flow through the hive. The presence of cracks between hive bodies means that you will have to wrap your hives to ensure that the bees do not have to cope with drafty conditions (Figure 6). Although it is not as critical to wrap a tight hive, wrapping will also benefit a well-sealed hive.
Beekeepers love gadgets, and as you might expect, there are several commercially available beehive winter wraps. You can make inexpensive and simple wraps yourself out of roofing paper, staples, and string. Cut a piece of roofing paper big enough to fit around the hive bodies with at least an 8- inch overlap. Staple the paper to the hive, at the overlapping seams and near the hive body corners. Reinforce the staples with a securely tied piece or two of twine. Trim any excess at the top of the hive to fit under the telescoping cover, folding the edges over the inner cover if you wish, but do not obstruct the hole in the middle of the inner cover. Cut through the paper at the upper entrance and also ensure that the lower hive entrance is unobstructed. You may wrap two hives together this way, offering each hive the additional insulation and protection of the other.
Push them close together. If you are using telescoping outer covers there will be a gap between the hives that you can fill with a piece of stiff foam insulation. Then wrap the two hives into one unit as described above. After the hives are wrapped together, to keep water from collecting and freezing between the hives, you can lay a piece of scrap plywood or similar across the top of the two hives, then strap it down or weight it with a heavy stone or piece of mortar.
Ventilation is critical to survival of overwintering bees. As the bees eat their honey and metabolize it to obtain the energy they need to heat the cluster, they produce carbon dioxide and water. Both of these metabolic waste products must be cleared out of the hive. Carbon dioxide dissipates readily, but excess moisture buildup in the absence of proper ventilation is common. Water condenses on cold surfaces in the hive….usually this means the underside of the covers….and this cold water then drips back down onto the bees. Wet bees in cold weather will soon be dead bees. Avoid this scenario by ensuring that there is a small upper entrance in addition to the lower entrance. A shim placed under the inner cover or a notch cut into the inner cover will be adequate to allow excess moisture to escape, and it also provides your bees with an upper entrance that they can use for winter cleansing flights if the lower entrance is blocked by snow, or dead bees. Orient your hive so that its entrances face away from the prevailing wind to help prevent drafts. You can also use the tarpaper wrap to make a flap that protects the lower entrance without blocking it. See Figure 4.
If your telescoping cover is not insulated, it helps to put a moisture-absorbent insulating layer over the inner cover. This can be as simple as a sheaf of straw, or as elaborate as a spare shallow super with a “pillow” in it made of burlap and wood shavings. A moisture-absorbing building
material called Homasote is gaining popularity again. However, one author (CW) remembers the use of Homasote as a hive-top insulation material during the 1960’s. Simple straw sheaves outperformed its moisture absorbency abilities, so we abandoned the use of Homasote. There are many inventive ideas you can try. The point is to increase hive top insulation as well as provide some absorption for any condensing moisture. Be careful not to block the upper entrance when you do this.
Make sure that the bottom entrance to the hive is open and remains uncongested during the winter. As bees die inside the hive….and they will…they may pile up at the entrance, obstructing airflow and impeding the ability of live bees to exit and conduct necessary cleansing flights during warm spells. Make a habit of visiting your hives about once a month, and clean out the lower entrances. (Your mouse guards should be removable for this purpose.) Have a slim stick handy that you can slip in at the entrance to sweep out dead bees. Take care not to knock on or otherwise disturb the colony, though, because when they are disturbed bees break their cluster and may easily become too cold. Do not worry if the lower hive entrance becomes blocked by snow. Air moves sufficiently through the snow to supply the hive, and snow also helps to reduce drafts.
Because beekeepers take honey away from bees, the other important “extrinsic” factor affecting winter survival is the quantity and quality of honey stores. This topic was covered earlier under “Fall Management”. Make sure your bees have sufficient stores to survive the winter!
Winter Beekeeping Tasks
Once your bees are tucked in for the winter, you might think that there is not much left to do until the spring thaw. But in some respects, what you do during this fallow period is critical in determining whether you will ultimately succeed in your beekeeping endeavors.
The most important work you can do to benefit your bees in winter is to think about and decide upon a summer management plan. There is probably a difference between the number of colonies you would LIKE to maintain, and the number you can actually manage. Other work and
family obligations are significant time commitments….as are your bees. Since beekeeping is physically demanding, it is NOT a practical means to a “retirement income”. It is, however, a wonderful hobby that you can downsize. As you age, you can adjust your equipment to medium or even shallow boxes as your physical strength dictates. It is also important to recognize that your landscape has an intrinsic “carrying capacity” for bees. Because local ecosystems vary greatly from one area to another, there is no one-size-fits-all formula for determining carrying capacity. Remember the adage “all beekeeping is local”, and learn through observation and experience what the upper limit of colony numbers is for your area.
Once you have a plan for the coming year, you can look at your equipment needs. Now is the time to scrutinize your Honey House (or garage, or shed, or wherever your beekeeping gear is stored). Would this be the time to organize your resources so that you can more easily find those entrance reducers, queen excluders, etc.? If you have a pile of culled frames, now is the time to clean them, and install new foundations. Some work will need to be done in relatively warm weather, such as painting or installing foundations, while other tasks are perfect for doing in the cold. If you use a freezer to freeze drone brood frames and store protein supplements and medications, for example, the cold winter is an ideal time to defrost and clean it. Your supplies can safely sit outside the freezer when the temperature is below 32°F (0°C). Other work to be done may include repairing or assembling hive furniture. What should be replaced? Are there supplies that are running short that need to be ordered? Is there painting to do?
Finally, it is a good idea to prepare for possible spring emergency feeding needs. Have a few gallons of 2:1 sugar feed available, or fondant if you need to feed as early as February.
In late February or early March it is time to check your hives to see if they are in need of feed. Bees that are low on stores will be up in the top box and you will see them when you lift off the outer telescoping cover (see Figure 3). Make plans to immediately feed hives in this condition.
If you do not see the bees when you tip the outer cover, there are two possibilities: First, the bees are doing well and have enough food. You can happily go home. Second, the bees have died, in which case you can just unhappily go home, or you can salvage something out of this, and stay to determine what happened to kill that colony.
How do you know if the colony is dead or alive without disturbing the bees? It is possible to hear them by placing your ear up against the hive body to listen. It is easier, however, to use a stethoscope. Apply the “bell end” of the stethoscope to the hive body, not the drum end, and make sure you have twisted the bell 180 degrees until it clicks into the correct listening position. With the earpieces in your ears, gently tap on the bell to make sure it is in this position. If the earpieces of the stethoscope are slanted, put them in your ears so that they angle forward, just as your outer ear canal does. You should hear a faint humming when you place the bell against the hive. If the colony is big or if the acoustics are good, you may hear a loud humming. Live bees always make some sounds. A hive that is silent is a dead hive. If you do not hear anything at first, continue listening at several other places around the hive. From the outside the colony may only be audible at one or two places.