Overwintered honey bee nucleus colonies: big solutions in small packages

Benefits of overwintered nucs

Overwintered nuclei can minimize colony losses by:

Correcting queen issues

The Bee Informed Partnership, a national Extension program focusing on developing best management practices to reduce colony losses, has found that queen events are a major contributor to short-term colony mortality. A “queen event” may be defined as a loss of a queen due to injury, departure of the queen with a swarm or a poorly performing queen in need of replacement. Nucleus colonies can be combined directly with queenless colonies to correct the problem. Because the nuc contains an accepted queen, the typical, caged-queen introduction process can be bypassed with the introduction of a nuc into a queenless hive. This process can be used to correct laying worker colonies and those with drone-laying, injured or otherwise underperforming queens.

The following are some benefits of using a nucleus colony to correct a queen issue:

• Colonies made queenright via introduction of a nuc do not sustain queenless or broodless periods that ultimately diminish adult populations.
• The risk of queen rejection is minimal compared to introduction of a new caged queen.
• Beekeepers establishing nucleus colonies in late spring and summer can purchase queens when they are readily available, well-mated and reasonably priced.
• A queen from an overwintered nuc has been proven. The beekeeper has had the opportunity to assess her egg-laying pattern and fecundity.
• The beekeeper is not obligated to return to the apiary to release a queen from the cage or check the status of an introduced queen.

Boosting weak colonies

Nucleus colonies can be directly installed into colonies that are weak or undersized. This boost is especially helpful in high-stakes situations such as when beekeepers are preparing to fulfill pollination contracts or when bees are vigorously foraging during a nectar flow.

Note: Nucs cannot be used to correct Varroa mite issues or American foulbrood. Before attempting to combine a nucleus colony with a weak hive, the beekeeper should identify and correct the source of the problem.

Creating nucleus colonies for overwintering

Nucs made from diseased or infested colonies will acquire the problems of the donor colony or colonies. Thus, they should only be established from strong, healthy donor colonies (figure 2). The donor colony should have no signs of disease, and the Varroa mite levels should be below the treatment threshold of 3% to 5% infestation.

Before assembling a nuc, prepare the following:

• Nucleus hive box with additional feeder top and a 1-inch ventilation hole covered with #8 hardware cloth on each of the short sides of the box.
• Appropriate number of empty frames as needed to fill the nucleus box.
• If necessary, some means of reducing the entrance to the nuc. The recommended entrance is 1¼ inches wide and five-sixteenth inches high.

Note: If making nucs early in the year, feeding the donor colony six weeks before making the nuc will help the colony gain the necessary food stores and population strength. A single nuc may be created from two or more colonies if colony populations are not high enough to provide adequate resources for a nuc. Conversely, if populations in a single colony are extremely high, multiple nucs can often be made from the same colony.

May 20: Before the beginning of the primary nectar flow

Nucs made this early in the season can outgrow the confines of the box very quickly. To avoid swarming, take care not to include too much brood in your nuc at this time of year.

To create a May 20 nuc, place:

• One frame of foundation in positions 1 and 5.
• One frame of honey with adhering bees in position 2.
• One frame of mixed brood (some capped brood and some open larvae) with adhering bees in position 3 (figure 3).
• One frame of drawn comb in position 4.

Introducing queens

Although skillful beekeepers can use nucleus colonies to raise queens, nucs intended for overwintering will be more successful if they are provided with a queen. If the nuc is forced to raise a new queen from the provided open brood, six to seven weeks will elapse before progeny of the new queen begins emerging. This can leave the nuc in a compromised state, with inadequate resources to survive the winter. For best results, purchase or procure a fresh mated queen from a reputable source (figure 4).

Caring for nucleus colonies

Once the nucleus hive is established and the queen is accepted, use the same care you would with a standard colony, with some modifications described below.

Controlling Varroa mites

Most medications and treatments are not dosed for nucleus-sized colonies and may do serious harm if they are used incorrectly. The doses for the following miticides may be adjusted as indicated for use in nucleus colonies.

• HopGuard II: One strip per five-frame colony.
• Apivar: One strip per five-frame colony.
• Apiguard: 25 grams (purchase tub of Apiguard with delivery pads as a vehicle for the 25-gram dose).
• Oxalic acid: 5 milliliter oxalic acid solution (see label instructions) between each frame of bees. Oxalic acid treatment may not yet be legal in all states. Check with your state department of agriculture or beekeeper’s association regarding registration of oxalic acid in your area.

As with all medications, it is critical to follow the label instructions closely.

Winter preparations

It is often necessary to feed nucs before winter. There are two main objectives of this prewinter feeding:

• Provisioning the colony with stores to last through winter. Each nuc should weigh about 45 pounds by the time feeding is stopped (figure 5).
• Allowing the bees to “profile” the brood nest into a consolidated sphere, with honey stores overhead and to all sides. It is critical that the brood nest is situated as low as possible in the nucleus colony, with a ceiling of honey stores overhead. The brood nest will slowly move upward as winter progresses. The position of the brood nest is as important as providing adequate food stores.

To accomplish these objectives, begin feeding with heavy syrup made with two parts sucrose (sugar) to one part water in August or as soon as possible after the nectar flow ends. Early feeding gives the colony time to process the syrup, profile the brood nest and avoid additional moisture in the colony when the weather may be cold and wet.

Nucs may be fed through the feeder tops using jars with perforated lids (figure 6). Shelter the feeding jars from sunlight while they are on the nucs. Syrup will expand as it warms and could flow out of the jar and onto the cluster of bees. If inclement weather arrives when quart feeders are in place, shelter nucs to prevent water from running down into the hive through the feeder openings.

Nucleus colonies are smaller than standard colonies, whose bee cluster generates adequate heat, and need insulation from the cold temperatures. Insulation should not block bee movement, and should be easy to install, remove and reuse. For best results, use a combination of rigid foam insulation board and roofing felt to protect the colony from rain.

• Cut three pieces of insulation board a few inches longer than the length of the nuc box. Cut an additional piece to fit at the back on the nuc.
• Using duct tape, secure the boards around the top, sides and back of the nuc. The board should extend beyond the front of the box (figure 7).
• Cut a sheet of roofing felt to cover the front, sides and back. Use strapping or duct tape to secure the felt (figure 8).

These components can be easily removed from the nuc in the spring and stored for future years.

Swarm control

Because nucs are much smaller than standard colonies, they swarm with greater frequency. The bee population will reach its lowest point about five to six weeks after the swarm date. This extended period of decline can leave a nucleus colony with too few bees to survive the winter. Therefore, swarm control is an important component of caring for a nucleus colony.

Options for relieving congestion of the nucleus hive include:

• Removing frames of brood from robust nucs to give to weaker hives.
• “Supering” nucs during the nectar flow by placing a nuc-sized box and frames above the nuc hive.

Spring management

Each year is different in terms of weather. In years with warm, mild winters, nucs can consume above-average amounts of stores. Beekeepers must be vigilant in assessment of colony weight as spring approaches. Depending upon the intended utilization time of the nucleus hive, emergency supplemental feeding may be warranted. Beekeepers should regularly heft nucs to become accustomed to the proper heft weight in relation to calendar date.

References

Steinhauer, N., K. Rennich, M.E. Wilson, D.M. Caron, E.J. Lengerich, J.S. Pettis, R. Rose, J.A. Skinner, D.R. Tarpy, J.T. Wilkes, J.T., D. vanEnglelsdorp. 2014. A national survey of managed honey bee 2012–2013 annual colony losses in the USA: results from the Bee Informed Partnership. Journal of Apicultural Research 53 (1): 1–18.