American Foulbrood in Honeybee: Symptoms and Management The spore-forming bacterium Paenibacillus larvae causes American foulbrood (AFB), a deadly bacterial disease of honey bee brood. It is not a stress-related illness and can infect colonies ranging from the strongest to the weakest in an apiary. Adult bees are immune to infection and only the immature larvae … Continue reading American Foulbrood in Honeybee: Symptoms and Management