Cause: A virus.

    Effect: Sacbrood is a widely distributed disease, but it usually does not cause serious losses. However, the beekeeper should learn to recognize Sacbrood so it will not be mistaken for the more serious foulbrood diseases. Sacbrood may appear at any time during the brood-rearing season, but it is most common during the first half of the season. Usually it subsides after the main honey flow starts.

    Symptoms: Scattered among the healthy brood are cells containing dead brood. Their cappings are dark and may be punctured or partly removed by the adult bees. About the time the cell is sealed, the larva dies. When it does, the head end turns up like the end of a gondola and remains in that position; also the pearly white color begins to darken, and the skin then becomes tough and the contents watery. At that stage, the larva, which resembles a liquid-filled sac, can be removed from the cell intact; hence, the name Sacbrood. The dead larva then continues to dry and harden until the dried-down scale is almost black. The head end is usually the darkest. Scales of larvae dead of Sacbrood can be removed from the cell easily.

    Transmission: The virus is probably fed to the young larva by the nurse bees in the brood food. It multiplies rapidly within the larva until it causes death. Then the house bees cleaning out the cells probably distribute the virus to other larvae within the hive. The disease is usually limited to one or a few colonies in an apiary.


American Foulbrood
European Foulbrood