Note up-turned head. A partly uncapped cell containing a diseased larva. A recently-dead larva. An old, non-infective larva. Colonies showing symptoms of sacbrood disease will often recover if moved to pollen and nectar flow conditions.
Evidence suggests that some lines of bees are resistant to the disease.
Each year, two to four of the oldest brood combs should be replaced with foundation. Old black combs are less efficient for brood rearing and are more likely to harbour disease organisms. Requeen annually using queen bees from a reputable supplier. Management of mild infections Requeening infected colonies is a recognised form of control. It is not practicable to requeen every colony which displays only a few larvae infected with sacbrood.