Brood combs in an infected colony have a scattered and irregular pattern of capped and uncapped cells. Infected cells have dark, sunken, perforated cappings. Dead prepupae/pupae within the cells change gradually from a healthy pearly white color to light brown and then to a dark coffee-brown. This color change is uniform over the entire body. The dead brood dry down into brittle black scales that adhere tightly to the cell walls. The scales lie flat along the lower walls of the cells with the rear portion curving partway up the bottom of the cell. During the early stages of decay—up until about 3 weeks after death—the dead prepupae/pupae have a glue-like consistency. The cell mass may string out when a toothpick is inserted and withdrawn; this is known as the “ropy stage.” When death does not occur until the pupal stage, a pupal tongue may stick up from the remains toward the top wall of the cell. This is one of the most characteristic symptoms of American foulbrood but may not always be present. In the early stages of the disease, only a few infected cells will be seen.

- Clarence Collison, Mississippi State University

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