Chalkbrood is a disease of honey bees (Apis mellifera), caused by the fungus Ascosphaera apis. It is widespread and found in colonies which seemingly appear healthy. The disease is most prominent in spring when colonies are building up populations. What initiates the disease is not completely understood, there are theories which suggest that high levels of carbon dioxide in the brood nest, which occur if there are insufficient bees to ventilate the colony, could be the trigger. Other ideas have been deficiencies of pollen or a genetic factor, in which case re-queening may be the cure.

Infection begins when A. apis spores are ingested by larvae and germinate in the gut. After larvae cells have been capped by house bees the infected larvae will die from strands of fungus which invade their tissue. Next they are covered with cotton-like mycelium which will fill the entire cell. The dead larvae will then appear chalky white, but quickly become hard and loose in the cell, at this stage they are known as mummies. Mummies are removed by house bees and can be seen outside the hive or on the floor.

Chalkbrood is not usually fatal to honey bee colonies, but can cause substantial production losses.

There are no medical treatments for this disease, but it can be controlled by bee breeding and good management.

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References:

Sanford, M.T. 2003. Chalkbrood recommendations. Unpublished manuscript, Entomology and Nematology, University of Florida, Gainsville, Florida. Retrieved from http://edis.ifas.ufl.edu/aa138

Honey bee disorders: fungal diseases. 2010. Unpublished manuscript, Entomology, University of Georgia, Athens, Georgia. Retrieved from http://www.ent.uga.edu/bees/disorders/fungal-diseases.html

Taxonomy:

Kingdom: Fungi

Phylum: Ascomycota

Class: Eurotiomycetes

Order: Onygenales

Family: Ascosphaeraceae

Genus: Ascosphaera

Species: apis