Life After Dearth: Summer Management for Winter Survival

August 13, 2019

As summer starts to wind down, the colony must begin producing bees that have a lifespan of five months, rather than five weeks. Understand the process that results in development of the winter cluster to guide summer management.
 
Successful overwintering is a simple matter of longevity. Interestingly, honey bees do not age chronologically. Their lifespan is highly variable and depends not on the number of days that have passed since emerging from the brood cell but on the intensity of the specific tasks they perform. For example, foraging reduces lifespan because it is inherently dangerous and metabolically demanding. Rearing brood also significantly reduces lifespan because it depletes the bee of vitellogenin, the critical egg-yolk protein fed to larvae in the form of royal jelly. These two principal tasks: foraging and nursing, have the greatest negative impact on life expectancy. Just being present in the brood nest is enough to accelerate behavioral development (aging), as exposure to brood nest temperatures and C02 levels cause vitellogenin to decline, as does the presence of brood pheromone. There exists a very strong, positive correlation between lifespan and stores of this critical nutrient. 
 
Bees that remain inside the hive but outside the brood nest experience a remarkable lack of senescence and have many times the lifespan of nurses and foragers. These do-nothing bees are produced as a direct result of summertime dearth. As the pollen shortage causes brood area to decline in midsummer, more and more newly emerged bees find themselves displaced from the brood combs. Only a portion of new bees are required to rear the declining number of larvae. The other workers are relieved of such duty and experience a delay in transition to forager, such that the winter cluster is composed of surplus labor that gradually accumulates inside the hive from late summer onwards. 

 

With all that in mind, the consequences of artificially extending the honey flow with syrup and protein supplements becomes obvious. Recreating the springtime brood rearing environment produces workers with a springtime lifespan. Feeding protein results in a well-fed queen that lays like June and nurses that ooze copious amounts of royal jelly. Just like springtime, most new bees must soon become nurses, as demand is high when brood is plentiful. Winter bee production is delayed until protein becomes scarce and brood rearing finally declines. In the meantime, a large population of shortlived bees is produced that crowd the hive in November and consume stores. Those stores are wasted. Rearing large amounts of brood late into the fall results in large piles of dead workers outside the hive entrance come December.


Under normal circumstances, a good way to prepare a colony for winter is to allow dearth to happen. Plenty of long-lived bees, fat on vitellogenin, will gradually accumulate over roughly a two-month period to form the winter cluster. Newly emerged bees don’t have to be fed supplemental protein to become fat. They are born that way. They only must retain those stores by not transferring them to the brood. Feeding protein stimulates brood rearing and therefore does not produce winter bees. It produces nurses. The colony’s truly young bees are those that don’t rear brood and don’t forage. They will far outlive the mass of chronologically younger bees that nurse an overfed colony in the fall. We’ve often been advised to feed protein and grow massive populations of “young” bees, because that’s what the professionals do. Little thought is given to the very different challenges that lie ahead for the recreational beekeeper.  


Practically every commercial beekeeper in Utah and beyond is destined for the California almond groves in winter. First, they will move their hives into holding yards in warmer climates that better support brood rearing. They will continue to feed and keep colonies strong ahead of the February almond bloom, at which point their bees will be foraging natural pollen during a spring-like expansion. Meanwhile, the hobbyist has colonies under a foot of snow and clinging to life with the same workers that populated the hive back in the fall. It makes every bit of sense for commercial beekeepers to maintain brood rearing at high levels throughout summer by feeding protein. That same technique may be problematic for the backyard hive.  


Although there is a well-documented delay in the production of winter bees in colonies fed protein supplements, some areas experience a natural late-season flow. There are several scenarios in which the colony may produce large amounts of late season brood without beekeeper influence. Most these colonies are likely to also experience a natural dearth in summer. By the time any fall flow arrives, the colony has already produced a sizable portion of surplus bees as brood declined during the dearth period. 


To be sure, feeding protein sparingly to colonies in need is not likely to cause major problems in the development of the winter cluster. “In need” is key. Feed such colonies early so there is still time for a dearth period ahead of winter. In that way, lifespan of emerging bees can increase, because the gradual reduction in brood rearing as protein sources decline lowers demand for nurses. Regardless of how much protein is fed late in the season, brood area necessarily declines as temperatures drop. With all the protein in the world, bees can only raise as many bees as they can keep warm. But weather is unpredictable and highly variable, as will be the size of the winter cluster. Again, don’t be fooled by a massive population of springtime bees as winter approaches. They are only draining resources. It now becomes clear why we are also advised to leave a hundred pounds of honey on the hive for winter. 


This strategy of feeding protein appears to rely on continuous brood production. Grow the colony so large they continue rearing brood uninterrupted throughout winter. In this way, lifespan is not a concern. It sounds familiar. Granted, this technique can produce large post-winter populations; however, there is considerable risk associated with the strategy. It’s reasonable to assume the springtime performance of an unrested queen and colony is compromised. And feeding pollen substitutes has been shown to increase the occurrence of nosema disease, which may be part of the reason nosema becomes such a problem in winter. The most disastrous consequence is a matter of mite reproduction. Brood rearing is mite rearing, but treatment options are poor for the clustered colony that continues to rear brood in early winter. Not a problem for the commercial beekeeper who can treat normally in winter in preparation for almonds, but again the hobbyist is hung out to dry with a growing mite population and very little power to manage it.  


Understanding the role of dearth in creating winter bees also will help decide the timing and size of summer splits or when to replace a weak queen. If a small colony is having to grow their population in late summer and fall, winter bee production is delayed. It may be delayed too long. Most colonies need time to produce the winter population, and there may not be enough of it remaining for a small colony that must first expand. A big colony is in better position to abruptly bring about dearth by discontinuing feeding. A queen laying like spring could conceivably produce a sufficient winter cluster in a couple of weeks. Winter bee production is a difficult thing to calculate under all the possible scenarios. That’s why it’s not a bad idea to just let dearth happen whenever that option is available.  


What if only syrup is fed but not protein? It’s unclear how large-scale honey processing in fall affects longevity of bees. There has been some limited research. Enzyme production is needed to invert sucrose so that it can be stored like honey. Producing enzymes is metabolically taxing ahead of the long winter. Of likely far greater importance is the difference in gene expression of bees fed sucrose syrup compared to honey, particularly as it relates to disease resistance. Disease is what’s killing our bees, especially during winter. The value of nectar as a nutrient is another topic. 


Feeding is a fundamental pillar of basic animal husbandry, but know the costs and risks associated with that decision. You can do more harm than good. Don’t be afraid not to feed when colonies have plenty of food and a strong population. If you’re not inducing the colony to keep rearing springtime levels of brood, the amount of stores required is far less. Don’t worry about a large population consuming all the honey stores ahead of winter because population is going to decline considerably during a dearth and a large colony can still forage profitably when resources are low. Let dearth happen. Ever notice how reluctant bees are to uncap honey? Pour it on top of the frames and it’s a stampede as very hungry bees crowd around it. If feeding is required, feed early. Allow the colony to get what they need and still have time to experience a dearth period ahead of winter. Hives have a natural tendency to depopulate in the fall. It’s how bees learned to survive the long, cold winters. Focus should be on the quality, not quantity, of the winter cluster. 

 

REFERENCES:

Dwindling pollen resources trigger the transition to broodless populations of long‐lived honeybees. HR Mattila, GW Otis, 2007

The Nurse's Load: Early-life exposure to brood-rearing affects behavior and lifespan. Amdam, Rueppell, Fondrk, Page, 2009

Aging without functional senescence in honey bee workers. O Rueppell, S Christine, C Mulcrone, 2007

Manipulating pollen supply during the fall does not affect the performance of winter bees. Mattila, Otis 2007

Timing of production of winter bees in honey bee (Apis mellifera) colonies. HR Mattila, JL Harris, GW, 2001 

Autumn Invasion Rates of Varroa destructor into Honey Bee Colonies and… E Frey, P Rosenkranz, 2014 

Seasonal change of the honeybee worker longevity in Sapporo, North Japan H Fukuda, K Sekiguchi, 1966

The effect of the size of colonies on food consumption, brood rearing and longevity of bees during winter. PA Racey, 1968

Characterizing the impact of commercial pollen substitute diets on the level of Nosema. J Fleming, D Schmehl, J Ellis, 2015
 
 

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