American foulbrood

American foulbrood is a notifiable disease. If you suspect a case of American Foulbrood report it immediately. See the reporting animal disease page for instructions.

American foulbrood is caused by the bacteria paenibacillus larvae. Bacteria infects larvae and kills it. American foulbrood will eventually kill a colony. There is no treatment for the disease.

Age of brood affected

Larvae 24 hours old are most easily infected. Larvae up to 10 days can still be infected.

Infection method

American foulbrood is spread by:

  • spores carried by adult bees
  • queens laying eggs in cells that are infected
  • contaminated honey.


Symptoms of American foulbrood are:

  • Discoloured larvae. Colour change will occur from 10 days after eggs have hatched. Larvae colour changes from glistening pearly white to:
    • yellow
    • light brown
    • dark brown.
  • Loss of segmentation in larvae. The segments on the larvae body will disappear.
  • Scaly larvae remains. Infected larvae will dry out to a dark scale and stick to the wall of the cell after 30 days.
  • Pepperbox appearance. Cappings on the cells develop holes and are slightly sunken.
  • Odour. A ‘gluepot’ odour may develop in the advanced stage of infection.

Basic testing

You can carry out basic tests for American foulbrood:

  1. Push a matchstick or twig into larval remains. A brown fluid will be drawn out and stretch between 3-4 cm. This indicates American foulbrood may be present.
  2. Check for dried scaly larvae. If a dried scaly larva cannot be removed without damaging the cell walls American foulbrood may be present.

Treating hives

A hive affected with American foulbrood must be closed immediately. Make sure the hive is sealed and remove it for destruction and sterilisation.

Diagnosing American foulbrood

American foulbrood can be diagnosed by sending us:

  • smears of diseased larvae on a microscope slide
  • sections of comb.
Send comb samples in a waterproof container.

Send samples to:

Apiary Unit
Primary Industries and Regions SA
33 Flemmington Street
Glenside SA 5065

Page Last Reviewed: 22 Feb 2018
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