I had four strong hives going into this winter. Three had the beetle buster bottom boards. I treated all four hives for mites prior to winter and the three with the beetle busters are now dead. I treated with Oxalic acid vaporization with a heated wand. On the beetle buster hives, I made a metal sheet to replace the diatomaceous earth board and put the wand on this sheet, below the corrugated sheet. I am wondering if maybe the holes in the corrugated sheet did not allow enough vapor to get into the hive to kill the mites. Has anyone else had this problem?