It is totally presumptuous to say we know what’s going through a colony’s mind, but it seems that bees swarm for two reasons: the colony is crowded or the colony wants to reproduce.
If the colony wants to reproduce, the “plans and preparations” have been going on for quite a while before it actually happens. It is very difficult to stop a swarm with the reproductive urge. Most steps you take will delay—rather than prevent—the eventual swarm.
Requeening in the early spring can help reduce swarming because young queens tend to produce more pheromone than older queens. As the amount of queen pheromone decreases the urge for swarming increases.
Cutting swarm cells is popular among beekeepers, but this often becomes a battle of wills: you keep cutting cells and they keep producing new ones. The beekeeper usually loses because if he misses a single cell or cuts a day too late, the swarm will issue anyway. Worse, if he unknowingly cuts the cells from a hive that already swarmed or is just about to swarm, he may leave the old hive queenless.
If swarming is imminent, one of the best things to do is split the colony in two. By splitting you are essentially initiating an artificial swarm during which you (try to) control when and where the bees go. By taking the old queen and some brood and nurses and putting them in a new hive, both parts seem to “think” they have swarmed and, if you’re lucky, they will both grow into strong colonies. Both colonies together won’t produce as much honey as one big colony, but you were going to lose them anyway so it doesn’t much matter.
If a colony has an urge to swarm due to overcrowding, anything you do to reduce congestion will help.
- Slatted racks give bees more room to cluster in the brood nest
- Follower boards between the brood box and frames give bees more room to cluster
- Screened bottom boards not only separate mites from the colony but provide better ventilation
- An upper entrance improves ventilation and decreases congestion at the lower entrance
- Reversing hive bodies keeps the brood nest lower in the hive and provides room above the brood nest to store honey
- Empty supers provide room above the brood nest to store honey
- Burr comb built between the frames should be cut away. Not only does the queen need lots of room to lay, but she needs to be able to get there easily.
If you do all these things you may be able to prevent a swarm—or not. In spite of all we know about bees, we are not bee psychologists. The best we can do is note what has worked in the past and experiment in the future.