Agriculture Reference
In-Depth Information
American Foulbrood
American foulbrood (AFB) is caused by the bacteria
Paenibacillus larvae
. This disease
is by far the most destructive one honey bees get, and it requires the most drastic actions
by beekeepers to avoid or eliminate it. AFB is spread by spores that are consumed by
larvae during their first couple of days in the cell. After that, they become immune to
the disease, but have already had ample opportunity to become infected.
You will probably never encounter this disease in your colonies. It is rare and well
policed, but it is so very serious we need to spend some time with it, first, so that you
can recognize it if it does show up, and second, so that you can efficiently deal with it
so that it doesn't spread.
Spores enter colonies in a variety of ways:
• Workers rob a wild colony, another apiary, or another colony in your apiary, and
bring home spores inadvertently through contact or in the honey they stole.
• Equipment previously contaminated is sold and reused.
• Frames are moved from a colony with AFB to one without it.
• Gloves and hive tools used when working a colony with AFB are not cleaned before
use in another colony.
A spotty brood pattern is always a sign of trouble, and is a first, best sign of American
foulbrood disease. This is your most obvious clue that a disease is present.
Spores are fed to larvae fifty or so hours old or younger—a very small window—and
the infection begins. Older larvae have a built-in resistance and are not affected. Once
ingested the spores germinate and begin consuming the larvae, much like the other dis-
eases mentioned. The larvae eventually die after the cell is capped. Before they die,
the larvae turn a brownish/yellow color. This is a sure sign that something is wrong in
a colony. Larvae should always be a stunning, nearly neon white. And they should be
shiny and glistening, not dull.
