Unhealthy larvae with yellow streaking leading to brown or blackish discoloration; dead, dying larvae twisted in cell rather than forming the normal C-shape.
European foulbrood (EFB) is a non-spore-forming bacterial brood disease caused by the bacterium Melissococcus plutonius. EFB is considered a stress disease and is most prevalent in spring and early summer, usually disappearing with a nectar flow. Occasionally, the disease remains active throughout the entire foraging season. All bee castes are susceptible to EFB.
EFB needs to be distinguished from American foulbrood (AFB) so colonies or equipment are not needlessly destroyed (only AFB requires destruction of adults and frames).
EFB is characteristic of open brood cells. When dying or dead remains are stirred with toothpick or stick, they do not rope out (although they may be sticky and gooey). The EFB scale does not tightly adhere to the lower cell surface. The odor is a rotting odor which is different from AFB odor but easily confused with the odor of dead and dying brood. These signs are very distinct from AFB disease, which is also caused by a bacterium.
It is possible to confirm an EFB diagnosis with an EFB test kit. If in doubt, consult a local expert for help with diagnosis or send a sample to the USDA Beltsville Bee Lab or to a local bee lab. EFB is treatable; colonies frequently recover as weather improves, resources become more abundant, and colony population grows.
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MAAREC. 2005. Bee diseases & their control. Mid-Atlantic Apicultural Research & Extension Consortium Publication 4.9. https://canr.udel.edu/maarec/wp-content/uploads/sites/18/2010/03/Diseases_of_Honey_Bees_PM.pdf
Mueller CM, Jack CJ, Mortensen AN, and Ellis J. 2020. Identification and Treatment of European Foulbrood in Honey Bee Colonies. University of Florida/IFAS Extension. Accessed 2023. https://edis.ifas.ufl.edu/publication/IN1272
Wilson M and Skinner J. 2019. European Foulbrood: A Bacterial Disease Affecting Honey Bee Brood. Bee Health. Accessed 2023. https://bee-health.extension.org/european-foulbrood-a-bacterial-disease-affecting-honey-bee-brood/
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