Even with the best of prevention methods you will get a swarm. Earlier this year I had done a walkaway split to a hive to prevent it from swarming. Still a couple of weeks ago I walk outside only to find a swarm on a cedar tree next to the hive. We quickly set up another hive to put the swarm into. The swarm is doing well although it is not likely to build up enough this year to produce honey.  The property still has blooms all over blooming strong.