In another thread it has been debated that Swarming is a planned activity verses a reaction to the local conditions.
I would say it is a reaction to the conditions, such as:
Excess incoming nectar
|Insufficient overhead storage space AND/OR a band of capped honey above the brood nest
----- Causes backfilling of the brood nest with nectar
----- Causes reduction of space for the queen to lay, so ovaries shrink
----- Causes less open/uncapped brood
----- Causes excess Nurse bees, unable to feed sufficent brood
----- Causes extra feeding of larvae
----- Causes Queen cells
----- Causes house bees to be used as nectar storage tanks
----- Causes wax makers to develop
- Swarming can be stopped by giving a few frames of uncapped brood, early in the process.
- Getting wax makers to build comb before swarm season starts and keeping them building wax helps to use up excess nectar and allow the queen to keep laying.
- Obviously, ensuring there is plenty of empty comb to fill with nectar, also helps to stop the brood nest from getting filled with nectar in the first place.
The amount of space needed to rippen nectar is often underestimated by the novice beekeeper. The bees will try to spread it out as thin as possible to gain the highest amount of surface area.
Temperature is also a factor to consider. It has to be warm enough.