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Insect ID Clinic


Honey Bee Diagnostic Services

American Foulbrood

Causative Agent: Bacillus larvae (Bacteria)

Range: Worldwide

Life cycle:

  • Young larvae can be fed as few as 10 spores to be infected.
  • As larvae become older they have to consume more spores to be infected. Full grown larvae rarely become infected.
  • Death occurs after the cell is capped.
  • The larva or pupae within the capped cell will decay in place and the tongue is often left attached to the top of the cell.
  • Progression of color: white→light brown→coffee brown→dark brown/black.
  • Cadaver, including the head, deflates uniformly, dries into a “scale” and strongly adheres to the bottom of the cell.
  • Consistency of dead brood is soft and becomes sticky and stringy
  • A single dead pupa can produce approximately 2.5 billion spores.
  • Spores can remain viable for up to 50 years.


  • Frequent inspections of the hives often reveal this disease before it becomes damaging.
  • When the infestation is low uncapping infected individuals will result in the hive removing the infected material.
  • Treatment with Oxytetracycline can kill this disease but several precautions must be taken to prevent the contamination of honey and other products.


Odor is not a reliable method of distinguishing this disease.

Irregular brood pattern can be a sign of a problem (but not necessarily American Foulbrood)

Other Useful Sites:

Information and Pictures of American, European and Sac brood Diseases

Mid-Atlantic Apiculture Research & Extension Consortium Disease Control

References used:

Root, A. I. (1990) The ABC & XYZ of bee culture 40 th ed. A.I Root Co. Medina, OH.

Morse, R.A. & R. Nowogrodzki (eds). 1990. Honey bee pests, predators and diseases . Cornell University Press Ithaca , NY .

printable pdf version


April 3, 2008