A week ago I relocated a few hives too over winter in a warmer area, two weeks before that the hives had been pushed down and mats installed. When I was picking the hives up, two of them had chalk brood, one quite bad, the pile below the hive was an inch or more deep. I removed the mats. Inspection yesterday after a week in the warmer weather, no chalk brood, also looks like they have decided to increase in numbers with full deeps covered in eggs. The question is, the mats or just the weather becoming damper and colder caused the chalk brood? Also, they now have access to tea tree which is starting to flower, don't know if that would help?