The spores germinate in the gut of the larvae and grow throughout the entire bee body as mycelium (fungal, thread-like filaments), turning the larva into a white mummy. If male and female mycelia merge, they produce sphere-shaped sporangia, enclosures in which spores are formed, and the chalkbrood mummy turns grey-green. The sporangia contain bundles of male and female spores, which are set free once these structures explode.
If only the female or male fungus is found in a larva, the mummies remain white, as no sporangia are formed. At first, individual larvae are infected by the spores. Larvae and prepupa are vulnerable to the spores. Open, infested brood members are removed rather quickly by the bees at the beginning. If the fungus is able to produce spores, it will rapidly infect more and more bee larvae. The brood combs will become spottier and the strength of the colony will subsequently decrease.
The colony could regain its strength and heal itself, if environmental conditions improve.
The disease is transmitted from colony to colony (landing at the wrong hive, robbery), but also by beekeepers (adding of brood combs with infected larvae, adding of contaminated combs and bees, contaminated equipment and hives, feeding of pollen or honey with contaminated with spores).
Strict selective breeding and due care when raising queens: use only chalkbrood free colonies for breeding or raising or filling mating nucs.
Young, strong queens; do not feed honey or honeycombs from colonies infected with chalkbrood; ensure sufficient food supplies; avoid moist, cool locations; keep varroa infestation as low as possible.
There is no licensed drug available on the Austrian market.