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The specialist international beekeeping organisation
There are a number of minor diseases and difficulties that can make the beekeeper wonder about the cause of the problem. Sometimes the symptoms can be confused with more serious diseases.
Chalkbrood is a common brood disease with a wide geographical distribution caused by the fungus Ascosphaera apis. It affects only sealed brood. The vegetative phase of the fungus infects the larval tissues with thread like 'hyphae' killing the larva inside the capped cells. The diseased larvae become hard, chalky-white or mottled grey 'mummies'. Where the adult bees detect the larvae have died they tear down the cappings to remove the larvae. These are frequently found on the floor of the hive or at the entrance. Chalkbrood is rarely serious although the sticky spores can be found even in apparently unaffected colonies. Some writers consider it to be a stress related disease and it is certainly most likely to affect colonies that are unable to care adequately for the brood so it is most prevalent in weak colonies. For instance, in colonies infected with varroa mites the effects of chalkbrood are frequently magnified and it has been observed that the fungus grows first on injured brood.
As with so many diseases, transfer of chalkbrood can be by any means that allows bees or combs to move between colonies. The use of pollen patties, especially where imported pollen is used, also aids the spread of fungal diseases. There is no specific treatment for chalkbrood so the best way to control it is to avoid conditions that allow it to develop. Strong colonies and bees that show hygienic behaviour are helpful while in serious cases, re-queening with a queen from a chalkbrood-free colony is recommended.
Pollen can become mouldy if infected by the pollen mould Bettsia alvei which renders the pollen useless for bees. Stone brood, a rare disease caused by the fungus Aspergillus flavus, transforms larvae and the abdomens of adult bees into stonelike mummies. It renders honey unfit for human consumption.
Both the lesser wax moth (Achroia grisella) and the greater wax moth (Galleria melonella can lead to a condition called bald brood. This occurs when the wax moths damage the cell walls and the bees remove the cell caps exposing the head of the developing pupae. Pupae have normal appearance but occasionally malformed adults can result. In rarer circumstances this condition can be caused as a genetic characteristic of the queen.
In some cases eggs, larvae and pupae can die for reasons that are never established. This may be part of a wider serious, but undiagnosed problem such as Colony Collapse Disorder (CCD or be a minor, unexplained individual problem. Sometimes the cause may be physical rather than something infectious. For instance, although young larvae can survive for several hours below the brood nest temperatures of 35°C brood can become chilled and die of cold and starvation when adult bees neglect them. A patchy brood pattern might result form a poor queen or one with a genetic defect in some of her eggs. Generally, these types of conditions are insignificant and rarely noticed by the beekeeper.