Seasonal guide to healthy colony management

Maintaining healthy bees means encountering challenges that change during the bee season. Here are some of the seasonal issues that will determine if you have success with beekeeping.

Virtually all locations for beehives will present a seasonal cycle as illustrated below. Winter is a dormantdormant:
a state of suspended or slowed physical activity; in honey bees, a period of winter clustering behavior
period when reduced nectar and pollen resources means the bees raise less brood. The length and intensity of this period obviously varies between southern and northern locations. The population increase can be very rapid in the spring for northern colonies and is longer and more spread out in southerly sites. The colony population peak varies by location. Swarming, or colony reproduction, may modify peak population size and when peak size is reached.

Beekeepers seek to time the peak population to coincide with the time of year when flowering plants are abundant and the weather is excellent for bee flight. This is termed nectar flow – for pollinator bee colonies, peak population is manipulated by the beekeeper so optimal population size coincides with the bloom of the target plant needing pollinators. The fall season features a decreasing population of both brood and adults in the beehive. Like the spring buildup, it may be very abrupt in northerly apiariesapiary:
a place where beehives and beekeeping equipment are located; also called a bee yard. An out-apiary is a site away from the owner’s residence.
and more extended for southern beekeepers. During the fall, the colony needs to rear enough healthy new adults to survive several months of the dormantdormant:
a state of suspended or slowed physical activity; in honey bees, a period of winter clustering behavior
winter season.

Seasonal cycle of bee population size; illustration by Honey Bee Health Coalition

Dormant season (winter)

Apiary in winter; photo by Dewey M. Caron

Bees are clustered within the hive during winter to preserve a central-heated core brood area. Depending on external temperature, bees may be fairly mobile, even flying from their hive at temperatures above 55 degrees F (12.8 degrees C), to increasingly tightly clustered when it’s below 55 degrees F (12.8 degrees C). The cluster consists of an outer shell of bees adhering to each other while the center core is kept warm enough (90-95 degrees F; 32-35 degrees C) to rear brood. In more northerly areas, brood rearing ceases for a month or more, whereas in more southerly sites there may be a low level of brood rearing continuously during this dormantdormant:
a state of suspended or slowed physical activity; in honey bees, a period of winter clustering behavior

Colonies can die during the dormantdormant:
a state of suspended or slowed physical activity; in honey bees, a period of winter clustering behavior
period; this is called a winter deadout. Deadouts should be evaluated to determine possible cause. The major reason for winter colony loss are: (1) starvation (running out of stores), (2) freezing (too few bees to keep each other warm enough to survive) and (3) mites. Mites feeding on adults and reproducing in capped brood results in a decrease in longevity and colony death as a result of a virus transmitted by the mites. Decrease in the length of life of adults with a decrease in the amount of brood reared in the fall are the major reason bees die over the winter.

Confinement to the winter hive leads to increasing levels of Nosema disease and tracheal mites in worker adults and incubation of the spring brood diseases European foulbrood (EFB), chalkbrood, and viruses such as sacbrood. Colonies with American foulbrood (AFB) will succumb in the fall or in the spring. Pests such as mice making nests in the hive or skunks externally visiting the hive at night, disturb colonies and may lead to death of weaker colonies. Any accidental exposure of the overwintering bees (tops blowing off or hives toppled) may also result in colony non-survival.

Increasing population (spring)

Spring is a period of population increase that starts with increased brood rearing. In southerly sites this period is drawn out and occurs gradually while for more northern locations this period can be short and the increase very rapid. Feeding a dilute sugar syrup and/or protein patties will improve development. During this period, colonies may prepare to swarm, the bees’ method of reproducing the colony, starting by raising new queens. As the colonies expand in numbers, additional boxes for expansion of the brood and/or supers for nectar surplus are added to hives. Threats to bee health are both external and internal to the beehive during the spring population increase period.

It is important to do a specific disease inspection of spring colonies. Diseases such as chalkbrood and sacbrood seldom kill colonies but may weaken colonies during the critical spring buildup period , depending upon severity. Spring brings potential exposure to pesticides and poisonous plants, and foragers outside the hive face numerous predacious insects/spiders and other occasional bee predators that might eat foraging bees. Surviving female varroa mites begin their reproduction in the spring. Scavengers in debris increase as the debris level increases. Bee populations that slow to develop or colonies preparing to swarm resemble colonies with health issues. It is important to diagnose reasons for poor or less than expected colony development.

Large spring colonies become very populous and make it difficult to detect developing health issues. Varroa mites may increase reproduction within drone brood cells during this time. Drone brood removal can be used to assess this reproduction, and removal of cappedcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
drone cells can be used as a means of reducing varroa reproduction, flattening the mite growth curve. Weaker colonies or new colony starts need continued vigilance.

Is spring colony population development normal?

Determining which overwintered colonies are strong, weak, or just right in adult orbrood populations (the Goldilocks effect) is one of the hardest determinations to make for new and inexperienced beekeepers. Maintaining more than one colony plus experiencing several different seasons helps with determining weak vs. strong. Recognizing the difference determines management choice. Weak colonies can be stimulated with sugar syrup or supplemented with adult bees and/or frames of brood transferred from a stronger colony. Strong colonies may outgrow their hive space and need to be weakened, by removing brood and adult bees for example, or they may swarm. Media posts from local bee clubs can alert individuals to seasons when bees are developing more rapidly or are delayed, which is usually related to environmental conditions.

Strong colony in spring; photo by Michael Palmer
Weak colony in spring; photo by Charles vanden Heuvel

Strong or weak refers to the adult but also the developing brood population. Initially, the adult population is unbalanced with overwintered older-aged bees. Rearing of replacement bees takes 21 days and colonies rear brood more slowly with the aged adult population. There is variation in queen egg laying with younger-aged queens, that are more likely to be better egg layers. Availability of pollen and foraging weather appropriate for flight are major drivers of spring colony expansion. Locations where early pollen sources are reliable favor faster expansion. Early spring weather followed by a cooler, wetter spring may dampen spring colony expansion; colonies may starve if they expand too soon, too rapidly, and then the weather limits their continued foraging for several consecutive days. Overstimulation by early feeding of sugar syrup and/or protein supplementation may help mitigate poor spring weather but can also lead to colonies growing rapidly and then preparing to swarm.

A common method to determine if a colony is weak or strong is to split the two boxes (assuming the colony was overwintered in two boxes) and look both below and from below into the top box (see photo of strong colony below). If in doubt remove frames and count frames with active brood rearing. If brood occurs on more than half of the frames consider it a strong colony. A weak colony may have brood with barely enough bees to cover on less than half the frames of one box, sometimes on only two or three frames. Colonies just right will have brood in both boxes (likely more in top box) and roughly half the frames will have brood with bees to cover. This assessment of size will vary with time of season of course.

Frame manipulations may help both weak and strong colonies. Transferring frames from stronger to weaker colonies is one option. Reducing the space in hive boxes might help weaker colonies; use solid boards to bring outside walls closer to better confine weaker hives. Reversing hive bodies, moving top box down to bottom board, and then placing the lowest box on top, helps ensure stronger colonies are more efficiently using comb space. Adding frames of foundation to stronger colonies and moving the drawn comb frames to weaker colonies is often of benefit. Moving frames of stronger colonies to spread out (expand) the brood rearing area is often useful. Be mindful of how bees are organizing their nest; you can do more harm than good by pushing expansion too early when resource availability is limited or when weakening colonies negatively affect your harvestable surplus.

Spring dwindle or pollen dearth

Feeding protein patties to nuc; shown is a double nuc in a standard box with divider and the top insulation pulled back on one of two nucs; photo by Dewey M. Caron

Dwindling or collapse is a general catch-all term for the sudden disappearance of bees (either adult population or entire colonies), slow development of overwintered colonies, or spring loss of colonies that initially survive the winter. Other names for this condition include disappearing disease, May disease, or spring starvation. Spring dwindling is more common in colonies that may be very weak from winter or in colonies that may have issues with older queens or queen replacementqueen replacement:
removal of an old queen and installation of a new queen in a bee colony
. In these cases, there usually are too few bees to grow from their weakest point and take advantage of the flowering resources spring offers. Colonies may dwindle and develop slowly and are still expanding while other colonies, developing normally, are storing potentially harvestable, surplus honey.

Dearth of pollen may result in a reduction of brood rearing, depending upon the amount of previously stored bee bread. Beekeepers supplement the protein of bee bread by feeding pollen supplements, which are protein with some pollen for attraction of workers, or protein substitutes, which consist of protein and sugar but no pollen. Recent studies have compared the adequacy of different protein supplements or substitutes. It appears there is a difference in colony response to fall and spring pollens, indicating supplements might need to contain pollens collected locally in the proper season for maximum effectiveness.

Break in brood cycle

The growing spring colony may have a break in the brood cycle due to the colony replacing its queen via swarming or due to an external factor such as pesticide poisoning. The management option of dividing the growing colony by making a split will also create a break in the brood cycle. Treatment with a miticide such as formic acid might also create a brood cycle break that may reduce overall population size.

A break in the brood cycle may not reduce the potential for a colony to store surplus honey if it occurs close to or during the nectar flow of peak population (see next section). In fact, it may free bees from nursing duties and add to the potential forager population, enabling the colony to store a larger surplus. A brood break created for mite treatment would enable use of oxalic acid treatment for the portion of the colony that lacks or has reduced capped brood. The queenless portion of such a colony will have this break in capped brood following transfer of brood to the split, which will emerge as adults before the newly mated queen can lay enough eggs and the eggs develop to capped brood stage. The split will lack capped brood and can then be treated for mites using oxalic acid (all the mites will be on adult bees, there being no capped brood for them to reproduce). The key for the beekeeper is management timing.

A brood break created by the beekeeper can be effective management, whereas a brood break created by the colony via swarming may limit the beekeeper from harvesting a potentially larger amount of surplus.

Peak population (summer)

Backyard deck colonies (8 and 10 frame) with supers; photo by Dewey M. Caron

During the summer peak population, most brood chambers are not examined, as it is necessary to remove the supers to get to the brood chamber. Beekeepers seek to manage supers, adding more or moving frames at the beginning and then starting the harvest at the end of this phase. It is important to harvest only surplus honey to avoid stress in fall colonies as they prepare for the winter. Health issues may persist in weaker colonies or show up in colonies that have been started as splits, purchased bees in nucs, or packages.

The spring diseases, especially EFB and the adult fungal disease Nosema, disappear as colonies bring in abundant resources and foraging weather improves. Colonies around crops in agricultural areas are in danger of pesticide loss. With peak population, the loss of foragers is less of an issue. Toward the end of this period robbing of a weaker colony by stronger ones is a possibility. Queen issues occur as bees seek to replace their single queen. Replacement may not be successful, and queenless colonies then become susceptible to health issues. If not supered in a timely fashion, the need to store nectar will result in the bees backfilling brood cells for ripening nectar, filling cells the returning queen could use to lay eggs for another bee generation.

Population decrease (fall)

Fall is the critical time to raise bees with heavy, fat bodies. These worker bees need to survive winter confinement in a healthy condition in order to keep the developing brood warm as day length increases. The major health issue of concern is the varroa mite load . Mite numbers need to be reduced to 2% or less of adult population to avoid an epidemic of Deformed wing virus (DWV) or other virus. Varroa control to flatten the mite growth curve should start early in the spring season. If mite populations are high at super removal, it will be extremely difficult to lower the mite numbers. The colony may look strong for a while into the fall but eventually will have a high probability of dying as mites interfere with the colonies ability to successfully overwinter. The colony may die in late fall or be revealed as winter deadout in the spring.

Fall colonies; note reduced entrances and slatted rack below the brood boxes; colonies have rain shield above entrance; photo by Dewey M. Caron

In addition to mite issues, a decreasing population might display signs of AFB. Thus, a second seasonal disease inspection should be done as the colony becomes smaller in brood and adult populations. Look for capped brood that doesn’t emerge, discolored cells, and cappedcapping:
the covering that bees add over comb cells containing fully ripened honey or to cap brood that has reached the pupal stage; bee bread cells are not capped
cells with tiny pinholes. The brood pattern may appear spotty. High mite numbers will also appear as spotty brood patternspotty brood pattern:
capped worker cells that are not uniformly solid within the brood sphere; numbers of cells lacking brood of the same brood age; indicative of poor colony queen or poor health 
, so spotty, inconsistent brood patterns must be closely examined. Queenless or weak colonies might have infestations of wax moth or small hive beetles. Yellowjacket predation increases in the fall, and foragers also face increasing populations of predacious insects/spiders or other animals.

The term for the bees reared in the fall is fat fall bees. The bees don’t look fatter in appearance; rather, bees reared in the fall have more fat bodies and larger quantities of vitellogenin, a protein found in blood and stored in their fat bodies. Such bees do relatively little brood rearing or other hive tasks and do not become foragers, but they do live longer. The fat fall bees need to live 5-6 months in northerly locations to enable a colony to survive the winter period. If a colony rears too few fat fall bees or the bees reared in the late season do not live this longer period, usually as result of mites feeding on them and spreading viral disease, then the colony will likely become a winter deadout.

Colony Collapse Disorder

In 2005-2006 colonies in several regions of the U.S. and Europe started suddenly collapsing. Apparently healthy, robust colonies lost their adult population in 2-4 weeks. All that remains are a queen with a very small adult population of mainly young bees and stores of honey and bee bread. Other names applied to similar conditions early on included autumn collapse, fall dwindle, and/or fall collapse. Colony Collapse Disorder (CCD) was different in that it apparently was more widespread. It certainly got more attention and publicity. No specific pathogen was found; after many studies, the likely causes are considered to be a mixture of mite-vectored viruses and perhaps Nosema disease.

Currently the fall demise of colonies is termed bee parasitic mite syndrome (PMS). Apparently healthy colonies collapse rapidly. No specific pathogen has been found as a causative agent in either the sudden spring or fall colony demise. Brood diseases such as snot brood, EFB, idiopathic brood disease syndrome, and spotty brood patternspotty brood pattern:
capped worker cells that are not uniformly solid within the brood sphere; numbers of cells lacking brood of the same brood age; indicative of poor colony queen or poor health 
), plus adult diseases and problems such as Nosema, chronic pesticide exposure, poor nutrition, varroa, and several bee viruses (deformed wing virus, Varroa destructor virus, Kashmir bee virus, acute bee paralysis virus, Israeli bee paralysis virus) are all possible interacting factors that can worsen with stressed bees or colonies and can lead to heavier-than-expected winter losses or poor colony performance in spring buildup.

Yearly seasonal cycle example

Here is a specific example of a bee season in the Willamette Valley of Oregon. There is an initial increase in the bee population (solid yellow line), then a dearth (when starvation might occur), then the sharp increase in population. The driver for the bees is the flowering period of nectar sources, which are shown below the population estimate as ranges when normal bloom occurs. This is an extremely diverse area for bees, with foragers visiting up to 200 different floral sources in a one year period. The second graphic shows the major management features of the bee season.

The graphic below is offered as an example. You should seek to determine the major plants driving your colony’s growth and eventual decline and the beekeeping tasks you need to do to ensure healthy seasonal cycles.

Different floral sources; photo by Dewey M. Caron
Yearly seasonal cycles for both honey bee forage and feeding and for beekeeping; illustration by George Hansen
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