Swarming bees are healthy bees!

How to use the self-healing capacity of bees

When bees are left alone in a favourable environment with low bee density and good food provision, they will survive for years without help from a beekeeper. This surprising observation in times of the Varroa mite has already been frequently confirmed all over the world, including in Europe. Swarming has been identified as one possible factor for their good survival. Why is this the case and how can it be integrated into our own beekeeping practice?

Dr Wolfgang Ritter Bees for the world

OIE, World Organisation for Animal Health, Freiburg, Germany

ritter@beehealth.info

What happens during swarming?

Only strong, vigorous colonies swarm. As a rule, a swarm consists of 2 kg i.e. around 14,000 bees together with the old queen, which together form the first, ‘prime’ swarm. Subsequent ‘after-swarms’ with young virgin queens are smaller in size. Some late swarms with only a few thousand bees are rarely able to survive.

A natural swarm consists mainly of worker bees over 18 days old, forming the cluster of bees crowding around the queen and scout bees. Only a few younger bees take care of the queen and the subsequent first brood. Before emerging from the hive, the bees have filled their honey stomachs so that they can survive for the days before new resources are available at their new nesting site. Swarms search for nesting places at a good distance from their original nest to minimise possibilities of subsequent transfer of diseases. And only healthy bees succeed in reaching the entrance holes of nests at great height.

In Africa the collection of swarms in trees has been an integral part of local style beekeeping methods. This is one of the reasons why Varroa mites and foulbrood do not stand a chance in Africa

Photo and illustrations © W Ritter

Collecting a swarm

How to collect a swarm

When collecting a swarm, one’s own health has priority. Better to leave the bees than to take dangerous risks!

• Take care that the ladder stands safely – ask a friend to hold it.

• Spray the swarm cluster with water.

• Put a swarm box underneath. If nothing else, a bucket will do.

• Jolt the bees into the container.

• Place the swarm box on the ground to allow the remaining flying bees to join it.

• The swarm has now ‘forgotten’ its origin and can be sited in a new place.

*The original article shows a diagram on how to collect a swarm which is not available on this mobile friendly version.

It is not easy to spot even a large swarm high in an oak tree – can you see it?

Photo ©s Bees for Development

Often it is the bees wings glimmering against the sun that catch your eye

Does swarming make bees healthier?

Bee swarms are generally carriers of the ubiquitous pathogens, i.e. those pathogens that are present in every bee colony. Among these there are fungal spores of the chalkbrood pathogen that is present in the bee’s cuticle (coat), and the Nosemosis pathogen in the bees’ intestines. Both of these pathogens can be found also in the food stored in their honey stomachs which have been fully filled before swarming. There are also viruses like the Sacbrood Virus and Chronic Paralysis Virus. Among the ubiquitous parasites are the Varroa mite and its specific viruses like the Deformed Wing Virus (DWV). During swarming the number of bees infested by mites and viruses is reduced. Moreover, most of the mites remain in the brood.

Swarming bees can spread the pathogens that cause American Foulbrood (AFB) and European Foulbrood (EFB). However, compared with infested brood, only in very small numbers. It is true for all honey bee diseases – that massively infested bee colonies – rarely reach a sufficient strength to enable them to swarm. Therefore, the transfer of pathogens nearly always happens from bee colonies that are only slightly infested, showing a healthy outer appearance.

What happens to pathogens and parasites inside the swarm?

The digestion of food carried with the swarm already starts during take-off for the flight, and continues during the time that the swarm is artificial swarm method or ‘shook swarm’ method. In the case of very strong infestation, or near to the focus of a large outbreak of foulbrood, the pieces of comb built during the first three days are destroyed in order to eliminate the spores that they contain.

Swarming limits multiplication of the Varroa mite, because of the interruption of brood rearing, both in the parent colony and in the swarm. Similar to the extraction of drone brood, this early reduction of the mite population leads to a considerably lower infestation rate later in summer.

When does a swarm get sick?

The honey bee colony’s selfhealing capacity is weakened when the swarm (or anticipated swarm) is collected and transferred directly on to comb foundation or ready-constructed combs. In this case, worker bees and the queen can immediately start breeding and the colony’s self-healing effect is greatly reduced. Foulbrood can break out, and the Varroa mite can continue to multiply without interruption. Using brood combs to create nuclei reduces or even inhibits the self-healing effect. Fortunately, most of the pathogens imported by a swarm do not cause the outbreak of a disease. An outbreak of those diseases may happen only in the case of unfavourable conditions occurring later. How well the honey bee colony survives disease – disregarding whether it was a swarm or not – will essentially depend upon the subsequent management and the infection or infestation pressure from the surroundings.

How to attract a swarm into a swarm box

An empty hive is successful as a swarm trap only if it has the aroma of a bee nest. However, in some countries it is not allowed to deploy a used hive for this purpose, and only new hives are allowed to be used as swarm traps.

To catch a swarm, the swarm box should:

• have a volume of 30 to 60 litres,

• have an entrance hole towards the south with a diameter of 10 to 15 cm 2 ,

• be treated inside with bee balm or a pheromone to attract a swarm,

• be hung in a tree, around 5 m above ground, or on a flat roof,

• be placed at a distance of at least 800 m from the mother colony, in order to catch its own swarms.

To anticipate swarming

There are different possibilities to artificially imitate the swarming process, as far as possible:

• Brush around 1-2 kg of bees into a new hive with frames or top-bars and starter strips.

• Add the old queen (if you are anticipating a primary swarm) or a virgin queen, or a queencell ready for emerging.

• Cut out all queen cells in the mother colony, except one, or anticipate more after-swarms.

• Place the artificial swarm nucleus around 2 km distant from the mother colony.

*The original article shows a diagram on anticipating swarming which is not available on this mobile friendly version.

Checklist

Only swarms that are easy to reach are collected. YES/NO

Swarms are trapped only in new hives. YES/NO

Colony multiplication is done either by natural swarming or anticipated swarming. YES/NO

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Even during an outbreak of American Foulbrood (AFB) disease, bees carry far less foulbrood spores than the infested brood. The bees can heal themselves only in swarms or in created nuclei without brood (anticipated swarm).

The same is true regarding Varroa mites. At the start of the spring season in Germany more than 90% of the Varroa mites are located in the brood. By the interruption of breeding, the number of mites in the swarm or the nucleus can be reduced considerably. Moreover, mite multiplication is also interrupted for some days in the mother colony.

Varroa mites on unsealed larvae

Photo © Vita (Europe) Ltd

A queen and worker bees. When a colony swarms, it is the old queen that takes the risk of leaving with half the workforce, to fly to a new nest site and to establish a new colony. They run the risk of the journey, of the new nest site being suitable, and of being able to find adequate forage over subsequent days and weeks to begin successful brood rearing.