Tom's suggestion of adding a frame of open drone brood to queen rearing colonies should solve the problem of Varroa infestation. However, the drone larvae will have to be fed and they will be competing with the queen larvae for a share of a finite quantity of royal jelly/ brood food. Without human interference the normal hive will produce only a few queen cells but a few hundred drones. It is likely therefore that the drones may be fed preferentially although this is an untested hypothesis. Perhaps the drone brood should be added when it is fully fed and ready for sealing. Chris Slade