American Foulbrood is extremely contagious and even though it only affects worker, queen and drone larvae less than 2 ½ days old, that’s sufficient to wreak total devastation on a hive.

The bee larva is unknownly fed the spore-forming bacteria by infected worker bees. The infection then multiplies inside the larva causing death. The dead larva will then harden into a black scale inside its cell. This scale is full of new foulbrood spores.

American Foulbrood can be recognized by a spotty mix of capped and uncapped brood cells. The capped cells having punctured or sunken tops while the uncapped cells will show the remains of rotting pupae hanging out of the tops of cells. You can also insert a piece of wood into a dead brood cell, you retrieve a sticky, gluey consistency, your hive is probably infected with American Foulbrood.

American Foulbrood spores can remain viable in beekeeping equipment for many, many years and the thing you can do is to destroy the colony and burn the equipment.


Terramycin can be fed to your bee population monthly to prevent the appearance of the disease. If you choose to use it, check with your state to see if its use is legal.