The Management and Prevention of Swarms

BBKA Magazine April 2017, By Dinah Sweet, MSc, MB, Dip. Apiculture (Cardiff University)

The ‘swarming months’ will soon be upon us and to help us prepare Dinah Sweet explains how to identify potential swarm triggers and how to respond appropriately.

You will see plenty of information on ‘swarm control’ in books and magazine articles, but I do not believe that even the most skilled beekeeper can always control a colony of bees. We just try our best to manage the bees’ natural instinct to increase themselves by swarming. There are many reasons to prevent our colonies from swarming, the main one being that we do not want to lose our best queen. We do not want to frighten our neighbours or the public by allowing our colony of bees to swarm. We also do not want to diminish the amount of honey collected or let the bees deplete themselves so much by swarming that they are too weak to survive the following winter.

Why swarming can happen

Swarming is a frequent occurrence in most races of Apis mellifera and the factors that predispose a colony to behave in this way are many, some of which can be managed. One trigger for swarming is congestion in the colony; either too many bees are crowded in the brood chamber with not enough space for the queen to lay, or there is not enough room for the bees to unload pollen and nectar.

An old queen producing low amounts of queen pheromone or a damaged queen with poor quality queen substance may also cause a colony to prepare swarm or supersedure cells in order to replace her. It can be difficult to tell the difference between these two types of cell, but supersedure is when a colony produces a new queen without swarming. It is said that supersedure cells are few and tend to be placed in the centre of a brood frame whereas swarm cells are more numerous and are found along the side or bottom bar of brood frames. They look so similar that you cannot tell them apart and both are vertical elongations of queen cups with an egg or larva inside. They are easily missed as bees often totally cover them up or they may be hidden in a crack between the wax and side bar of a frame. Beekeepers often panic when they see queen cups but until they are loaded with a larva floating in royal jelly, nothing needs to be done.

The third type of queen cell is an emergency cell, produced at the sudden loss of the queen and not built in response to the swarming impulse. Emergency queen cells look different as they are made from converted worker cells that already contain a very young larva, being part horizontal and part vertical, looking like a broken nose from the side. When these are present the colony will not swarm but it will allow only one queen to survive.

It is important not to panic when you see a queen cell; being able to recognise the different cell types will make this easier for you. Whatever type they are, stop and plan what to do next and on no account destroy them as it will only frustrate a swarming colony and render a colony with no queen totally queenless, with no eggs or larvae of the correct age to turn into a queen.

You can help mitigate swarming by following good beekeeping practice, such as:

  • Adding drawn comb to the brood chamber when needed.
  • Replacing old and mouldy frames.
  • Timely addition of supers just as a honey flow has started, because this may also delay swarming.

A few beekeepers say that not using a queen excluder, especially with Carniolan bees, prevents swarming. However, even with a young queen heading a colony, it may still decide to swarm especially if the weather confines the bees to the hive for a few days or if the forage stops suddenly.

Signs that a colony is preparing to swarm

There are few signs that a colony is preparing to swarm as even the odd egg in a queen cup may not lead to anything and be eaten by the worker police bees. Knowing local conditions and seeing the bees progressively expand in number will give the beekeeper an idea of when to start weekly inspections. These can be extended to ten-day inspections if the queen is clipped, but it will not prevent swarming. The appearance of drones in the colony also indicates peak build-up and so the beekeeper may do a pre-emptive split early in the year to prevent swarming. However, this may only delay them and they still may decide to swarm!

The queen is starved for a short while before a swarm emerges from its hive, as she needs to be light enough to fly with the prime (initial) swarm, but this makes her a lot more difficult to find. She leaves the hive with anywhere between 20% to 60% of the bees, usually as soon as the first queen cell is sealed, so the beekeeper must inspect regularly even if it is cold or raining. This must be done quickly without chilling the unsealed brood and will become a smooth operation with experience.

Measures to help prevent swarming

Many books advocate cutting out queen cells at first, but this only frustrates the colony and the bees will soon produce more cells from older larvae. The old queen may have already gone with the swarm that you have missed, although the colony may seem to have just as many bees in the hive as before, leaving an inferior queen or no queen at all. It is really important to have collected or made plenty of spare equipment early on in the year and work with the bees, so as soon as queen cells are seen, you do not go into panic mode but have a sensible plan of what to do next.

What to do when swarm cells are found

By engaging with the bees and using their swarming impulse as a positive factor, an artificial swarm method can be put into action when unsealed ‘swarm’ queen cells are found. If the queen cells are already capped, there are no eggs and the queen cannot be found, it is probably too late. However, she may still be around and if marked, she is much easier to spot. It is always a good idea to have a nucleus box on hand when doing an inspection so that if you do find the queen, put her with the frame she is on, in the nucleus for safe keeping. It is now that you need spare equipment and the excuse that you have not managed to put anything together yet will not do as the bees cannot wait.

The old hive with the majority of bees, brood and queen cells should be placed about five feet from the original site, with the entrance at right angles to its original position and it should be made smaller. A new hive comprising a floor and brood chamber with frames mostly of foundation, should be placed on the original site. The frame with the queen on in your nucleus box can now be moved to the middle of the new brood chamber and if there are any swarm cells on it, these should be removed. Perhaps put another drawn frame next to this containing some pollen and honey just in case the weather is poor for a few days. A queen excluder and old supers plus new supers (when needed) can then be put above this new hive. Flying bees will join the old queen in the new boxes on the original site and as there is very little brood here, the colony will resemble a swarm. As there is plenty of room in the new hive, queen pheromone will spread around quickly and the colony is unlikely to swarm again that year. At first the bees will soon pull out the foundation and put honey in the supers, but as the queen gets down to laying again the normal division of labour will continue.

Ensure varroa is controlled in the original hive

As most of the brood is in the old hive on the new site, if this has a varroa problem, then it could be treated with a miticide, such as Apiguard or MAQS. You must follow the instructions carefully on each medicine packet. There will be no honey present to contaminate with the treatment.

The old colony containing queen cells may still decide to swarm if it is too strong. If this is the case it could be split into two, making sure each part is a viable unit and contains at least one queen cell. They may also need feeding as most of the foragers will have returned to the new hive on the old site. That is why it is best to wait a few days before feeding as some of the bees flying back to the original site may tell the others and ‘silent’ robbing may take place. It will take up to four weeks for the new queen to mate and start laying. Allow only a quick look inside to check that the queen cell has hatched but otherwise do not disturb it. If you want to return to just one colony later in the season, then you can remove the old queen and unite the two through newspaper, keeping the queen-right colony on the bottom. A week later rearrange the frames or overwinter the colony on a double brood.

“By engaging with the bees and using their swarming impulse… an artificial swarm method can be put into action when unsealed ‘swarm queen cells are found”

I have found this artificial swarm method, often called the Pagden method, using separate hives, to be the simplest and most successful. If the new colony tries to swarm again the procedure can be repeated. There are many adaptations to this where the part with the swarm cells is placed above the new hive on a floor with the entrance facing a different way, e.g., Demaree method, Snelgrove method. Although these methods save on some equipment, I have witnessed many problems with them, from overheating in the top box to starvation of the bees in the lower box. They are often too complicated for beginners and the beekeeper is confused as to what is happening in each box.

It may be that however frequently you inspect your bees, queen cells are not recognised or hidden by the bees and you see a swarm departing over the hedge. You can still prevent cast swarms by going through the colony carefully and leaving just one open queen cell, removing all others using a bee brush to check in those awkward places. A bait hive in the apiary, containing frames with at least one old but clean frame that really smells strongly of beeswax, may also lure a swarm to settle down, if regular inspections are difficult. For more information about bait hives turn to page 125 in this issue where Bridget Beattie describes these in detail. When I first started beekeeping I followed advice from old books and tried banging a dustbin lid to get a swarm to settle. This really did not work! A hose held over the swarm making them soggy but not too wet will be more effective.

May and June are the months of the year that a colony is most likely to swarm, so avoid going off on holiday then, have plenty of spare equipment ready, keep your hive records up-to-date so you know the age of each queen heading a colony and make sure your queen is marked so that she is easy to find. A swarm can happen at any time from April to September, but regular inspections should help you to ‘read the hive’ and come up with the best action plan.