Submitted to: Compendium on Alfalfa Diseases
Publication Type: Book / Chapter
Publication Acceptance Date: December 5, 2012
Publication Date: N/A
Technical Abstract: Cylindrocarpon root rot of alfalfa has been found sporadically in Canada and the northern United States. The etiology of this disease is not fully understood, but the priority for research has not been high because of its infrequent occurrence. The infected area of the root initially has a water-soaked appearance, usually just below the crown, but soon turns light brown and finally dark brown. The entire root system may rot as a result of severe infection, but often the infected area extends only a short distance below the crown and the remainder of the root appears sound. Sclerotium-like stromata develop in cracks in the root bark and, when mature, give the root a dark, rough appearance. Cylindrocarpon ehrenbergii was initially reported to be the causal agent; however, the identity of the pathogen is unclear because this name was not supported in taxonomic revisions of the genus. At present, C. ehrenbergii is a synonym for C. obtusiusculum (teleomorph Nectria ramulariae). Several other Cylindrocarpon species have been described as causing root rot of alfalfa, all of which appear to be weak pathogens.