Test done in germany by sraying syrup/thymol mix onto combs and bee's caused .
Carnica was very good against chalkbrood. It bursted at once when I returned to Italians.Did you get much chalkbrood when you had carnica,or were they not in the hives long enough before they swarm.
Change the queen. You cannot clean it. You may handle stores and comps with ice acetic but diseases are among living bees and combs in use.Is Chalkbrood easily transferred from one hive to another and what is the best way to clean the hives so it is not spread around?