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American Foulbrood 2: Identification and Management

Identifying and managing American Foulbrood is essential to control it’s spread.

Last week on The Buzz we took at what American Foulbrood (AFB) is and how it spreads. In part 2 we take a look had how to identify AFB and distinguish it from the many other brood diseases, and what you can do to manage an outbreak.

Identifying American Foulbrood in a Honey Beehive

American Foulbrood does not always develop quickly but early detection is very important.

  • Both strong and weak colonies are susceptible to AFB and colonies can be infected at any time of the year
  • Brood combs should be thoroughly examined for AFB at least twice a year (Spring and Autumn)
  • Early infections may only have one or two cells showing disease signs
  • At this stage you won’t see much effect on the adult population, so you must inspect all brood combs closely.

Remove each brood frame from the colony, clear away bees and examine the brood frame for the following symptoms:

  • Irregular and patchy brood pattern
  • Sunken, darker coloured or greasy cell caps
  • Perforations in cappings (from bees trying to remove the dead brood)
  • A sulphurous smell

As the disease advances:

  • You will notice larvae changing from a healthy pearly white to a dark brown
  • Dead larvae will become tough but brittle scales that are difficult to remove from the cell
  • If you hold the comb to sunlight the scales will reflect it and become visible
  • In AFP, the scale is impossible to remove without breaking the cell walls
  • Other brood diseases can cause scales in cells, but these will readily separate from the cell wall
  • In infected pupae, the mouthpiece or ‘tongue’ may become stuck to the top of the cell wall
  • As more brood is lost to the disease, the number of adult bees will significantly drop over a period of two to three months or more

The ‘tongue’ symptom it is almost a 100% confirmation of AFB, but tongues are not always present in in every AFB infection.

Beekeepers should try to detect AFB before the disease reaches the scale stage. This can be done with a “Ropiness Test”:

  • Find a cell showing AFB symptoms i.e. discoloured, greasy, perforated or sunken cappings
  • Push a matchstick into the infected cell
  • Slowly withdraw the match
  • If the contents of the cell can be drawn out in a thread, i.e. if it is ‘ropey’, you have a brood infection
  • AFP will usually form a thread of at least 2.5mm and can form a fine ropey thread of around 3-5cm.
  • The ropey thread of AFB is generally a dark brown and quite elastic
  • AFP will be accompanied by a sulphurous odour
  • If the drawn-out cell contents only form a short (usually less than 1.5cm long), grey semi-liquid mass, then the disease may be European Foulbrood.
  • Sometimes EFB can resemble AFB, but unlike AFB, larvae will die before capping
  • It’s essential to monitor the brood closely to identify these patterns early on
  • Note that the only accurate means 100% confirm EFB or AFB is a lab test

Management of American Foulbrood

American Foulbrood is a reportable disease. If you think you have an infection contact your local state or territory Department of Agriculture.

Good hive management practices will help prevent the spread of undetected infection:

  • Always clean tools between inspecting hives
  • After winter shutdown, always return supers to the original hive in spring
  • Numbering both the hive and the super can ensure there is no mix up
  • Brood combs should be replaced every 3 to 4 years

If American Foulbrood is detected in a colony, it must be destroyed:

  • Kill the colony (including the frames) and irradiate all box parts to destroy the AFB spores
  • If irradiation is not possible, place all hive components in a deep pit to be burned
  • Ensure that the hive entrance and any other openings are closed so that bees cannot escape
  • Once the hives have been burnt, bury the remains in the pit
  • If you are unable to do this yourself, contact your Department of Agriculture for help

As heartbreaking as it may be to destroy your bees in this way, it is the only way to stop the spread of this horrible disease. You will be protecting your other hives, and those in your surrounding community.

Sources:

BeeAware – American Foulbrood

Rural Industries Research and Development Corporation – Australian Beekeeping Guide

Drawing of a honeycomb infected with American Foulbrood. Everett Franklin Phillips [Public domain].

Read more from The Buzz.

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