Drone frame, one style = 2 inch from foundation is clipped away, or better, you put Farrar foundation into Langstroth frame. Bees make drone cells and when broo are capped, you cut them away and catch 50% mites from hive.
Also drone cell building is in better order when bees have place to raise drones. Otherwise cells are everywvere.
So, how many of your use this method to kill mites?