Ascospharea apis aka…Chalkbrood

Although chalk brood has a global distribution, little is

Culturing A. apis
Culturing A. apis

known about Australian strains of A. apis and its virulence toward honey bees.  We are working to rectify that!  Here are some pictures of culturing A. apis from chalk brood mummies last month.

Ascosphaera apis is the fungus that causes chalkbrood disease in honey bees.  The spores of this fungus are extremely hardy and can stick around in honey, wax, pollen, bee bread and the hive architecture for up to 15 years!  Bee larvae are fed the spores at about 3rd instar and if the conditions are right in the larval gut, the spores dormant and begin to grow hyphae.  These hyphae puncture the larval gut lining and eventually the larval cuticle.  The hyphae then grow all over the outside of the larva causing death about 3-5 days later during the 5th install- just as the larva is being capped over,

A. apis in culture
A. apis in culture

elongating in the sell and preparing to pupate.

If a larva succumbs to chalk brood infection the dead body will dry up and become a chalk-like white mummy in the brood cell.  This type of fungus needs two mating types to reproduce.  When hyphae of opposite mating types come onto contact, ascocarps are formed which is essentially a big spore cyst that contains smaller balls that contain spores.  These ascocarps turn the mummy black and when they rupture distribute spores through the colony further spreading disease.

Ascocarps of A. apis
Ascocarps of A. apis
Hyphae of A. apis
Hyphae of A. apis

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