Chalkbrood is a mycosis (a disease caused by a fungus), which affects bee brood.
It is an infectious disease of the larvae, and is caused by a fungus called “Ascosphaera apis”. It looks like pieces of chalk in the comb and is chalky-white initially, but some become dark blue-grey or almost black as in the picture to the right.
The disease mostly occurs in the spring and worsens in the summer, generally disappearing in the autumn when the queen slows down laying. It causes the death and mummification of sealed brood (see the picture to the left) and seriously weakens the colony, affecting honey output and the general health and well-being of your bees. Fortunately, it only very rarely kills a colony.
The larvae in the comb ingest the spores of the fungus with their food, allowing the fungus to get into the intestine of the larvae. The young infected larvae do not usually show signs of disease, but they usually die within two days of being sealed in their cells or die as prepupae. The spread of chalkbrood within the colony is very limited, and the fungus only seems to thrive on honeybee larvae and does not appear to affect the adult bees.
Pieces of Chalkbrood
The fungus grows best when the brood is chilled, so keeping a constant temperature within the hive is a major factor that can help to keep infection at bay. The spread is usually due to the accumulation of mummies (the white chalky remnants of infected bee larvae) and the bees being unable to remove the dead bodies from the hive fast enough.
It is mostly spread between colonies through the activity of the beekeeper, on clothing and tools – another reason why good sanitary practise and careful beekeeping husbandry is essential. The spores can remain dormant for more than 3 years anywhere in the colony, including the wax foundation and frames, this means that the disease can return in previously infected colonies.
Chalkbrood is not just a problem in the UK, but is present on nearly all continents. The only place chalkbrood is not a problem is in Antarctica, and that’s only because there are no bees there! Some beekeepers are lucky enough that their colonies never suffer from chalkbrood, but it can be a harsh and serious problem if one of your colonies does!!