Swarming is an instinctive habit in a beehive, but through careful maintenance you may be able to prevent a swarm.
Watch for overpopulation. The brood nest must contain plenty of empty cells in which the queen can place her eggs.
Relieve congestion by removing full frames of brood and replacing with frames of wax foundation that need to be built into comb. This will give the queen new places to lay her eggs.
Separate the brood and the queen.
Place the queen with unsealed brood eggs and bees in the lowest brood box.
Place another brood box with foundation above the lowest box.
Place a super filled with capped brood and the rest of the bees on the next level up.
Check for poor ventilation. Provide some shade and stagger the supers for ventilation.
Provide access to an abundant source of water to help keep the hive cool.
Remove the entrance block.
Prop the corner of the top cover open using twigs or small blocks of wood.
Split the hive, or create a false swarm. If the hive has queen swarm cells, you can remove the old queen, a few frames of brood and food, and start a split or NUC, a smaller hive. A new queen will emerge and take over the old hive.
Signs of Swarming
Check to see if the worker population is increasing rapidly.
Watch for drone rearing to begin as the workers' number increases.
Beware of the situation where the brood nest holding eggs, larvae and pupae cannot be expanded because combs are already occupied with brood or honey.
Look for queen cup construction to begin at the lower frame edges.
See if the queen has deposited eggs in the queen cups; the number of young brood has decreased; and the queen appears restless.
Examine the hive for queen cells that are capped or sealed; queen cells containing larvae that vary somewhat in age; and field bees becoming less active and beginning to congregate at the hive entrance.