American foulbrood
Updated
On this page7
Why this one is different
eXtension is blunt about why AFB is singled out: virulent pathogenicity, ease of spread, and limited control measures. It is rare, and it is treated as a regulatory matter rather than a husbandry one because a single infected colony can seed an apiary and everything a beekeeper carries between hives can move it.
The spores are the reason. They survive in equipment, in comb and in honey for decades, which is why the disease outlives the colony it killed and why second-hand equipment is how it usually arrives.
What it looks like
- Sunken, greasy, perforated cappings rather than the dry domed cappings of healthy brood.
- A scattered brood pattern, because dead larvae leave gaps.
- Coffee-brown larvae collapsed along the lower cell wall.
- A smell that people describe as glue-like and do not forget.
- Scale: a hard dark deposit stuck to the cell wall that cannot be removed.
The rope test
Push a matchstick into a suspect cell and withdraw it slowly. AFB-killed larvae draw out in a brown rope an inch or more long. European foulbrood does not rope the same way, and the difference matters enormously because one of them is reportable and the other is not.
Confirming it
Field diagnostic kits for AFB and EFB are available from the major beekeeping supply companies at around $14, with step by step directions, and eXtension describes them as easy and reasonably reliable. That is a small amount of money against the consequences of guessing in either direction.
What happens next
Contact your state apiary inspector. In most states this is not optional, and inspectors are generally helpful rather than punitive because containment is their whole purpose. The standard outcome is destruction of the colony and burning of the frames and comb.
Prevention
Do not move comb between colonies casually. Be careful with second-hand equipment, which is the usual route in. Never feed honey of unknown origin back to bees, because spores travel in honey.