Bringing honey bees successfully through the winter

Five questions to Dick Rogers, Bee Health expert Bayer Bee Care Center North America

When beekeepers get together, they usually discuss a wide range of apiary challenges, but there is one vital question they never fail to ask: How have your colonies fared over winter?

With the cold season 2013/14 just around the corner in the Northern Hemisphere, we asked our expert, Dick Rogers, to highlight some DOs and DON’Ts for bringing honey bees successfully through the winter.

Q1: Dick, before we go into what the beekeeper can do, can you tell us how the honey bees themselves prepare for winter?

Honey bees take a long-term approach to their colony’s survival. As early as mid-August, the colony starts producing winter bees. These bees are physiologically different than summer bees and are well suited to surviving long winter periods confined to the hive. Whereas summer bees only live for 4-6 weeks, winter bees can live 4-6 months. Gradually the summer bees die and are replaced by winter bees.

Also, in feral colonies, honey bees will work all summer to obtain the food needed for colony growth and they store a surplus of honey as food for winter. In managed hives beekeepers often harvest at least some of the surplus honey, so sugar syrup has to be fed back to the bees so they can ripen it to form honey

Q2: What does it take to get bees successfully through the winter?

The survival of a colony over winter depends on three key principles. All of these principles must be satisfied for successful wintering. First, the colony must have a large, healthy population of winter bees and a young, healthy, productive queen. Ensuring a low population of Varroa helps achieve a healthy colony status.

Secondly, there must be sufficient food stores that are accessible to the winter cluster of bees.

And thirdly, the hive must be protected from wind and water infiltration, yet ventilated enough to prevent condensation. In the north, condensation in a hive over winter is lethal to honey bees.

Q3: What can a beekeeper do to help the bees in overwintering?

It is essential that beekeepers manage bee health issues throughout the season and that these issues are fixed by early August, preferably sooner. Winter bees produced in a Varroa or tracheal mite infested colony, or in a colony with other health issues like viruses or Nosema, will not be healthy and will have a much shorter life span.

A full size colony needs about 27 kg (60 lb) of easily accessible ripened honey to get through the winter. This amount normally is sufficient to get through times of higher consumption and delayed springs, however, beekeepers should always monitor honey stores in early spring to ensure the stores are still adequate. In the north, to help the colony obtain enough honey stores, beekeepers should start feeding the bees continuously  by mid-September and finish feeding by end of October or sooner. The objective is to feed enough sugar syrup early enough that the bees can store and ripen it before temperatures drop and the bees have to form a cluster.

The beekeeper can also support the bees by making sure the hive is adequately ventilated to avoid condensation in the hive – which usually means having small upper and lower entrances. Good air drainage is important to help avoid standing high humidity air. This can be achieved by not placing hives in hollows and low land where airflow becomes trapped by the landscape features. Also, protect colonies from high winds, water pooling and flooding.

In southern climates, there may be no break in brood cycles, bees may only need to form clusters occasionally, and the bees are not confined to the hive for long periods because of low temperatures. The conditions are vastly less severe than in the north, however, food is still a critical issue so beekeepers may need to feed colonies often to compensate for potentially long periods when natural forage is not available.

Q4: What are the things to avoid during the cold winter months?     

Even though hives need adequate ventilation during the winter months to avoid condensation issues, it is important not to break the propolis seals between hive components after temperatures drop below 10°C (50 F). The propolis seal protects the cluster from wind and rain.

And another thing to avoid: Don't disturb the colony when bees are clustered around the queen and brood to keep them warm! If the cluster is disturbed, the cluster temperature will drop rapidly and the bees may not be able to reform the cluster and therefore individual bees and eventually the whole colony may perish.

Q5: Once the worst of the winter is over, how do the bees prepare for the new season?

During late winter to early spring the winter bees start dying off and the production of new generations of summer bees start slowly. As soon as the first pollen is available, the queen starts laying in earnest and three weeks later the colony should start growing quickly.

Good sun exposure is useful in the spring because it can provide adequate microclimate for cleansing flights to occur which are important to rid the colony of dysentery and Nosema.

Spring dwindling in the colonies occurs during that critical period when the winter bees are dying off and new bees are starting to emerge. If the emergence rate does not exceed the death rate of bees, then the colony will dwindle in size and if this situation continues, the whole colony could die. In a long winter colonies may not be able to produce enough bees to replace losses and this can lead to neglected brood which can also contribute to failure of the colony to reverse the dwindling effect.

Also, if there is a false start to the season, food stores may become depleted very rapidly and natural forage will not be available. This situation puts the colony at risk of starving to death.

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