Page Banner

United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING ALFALFA AND OTHER FORAGE CROPS FOR BIOENERGY, LIVESTOCK PRODUCTION, AND ENVIRONMENTAL PROTECTION

Location: Plant Science Research

Title: Violet root rot

Author
item Samac, Deborah

Submitted to: Compendium on Alfalfa Diseases
Publication Type: Book / Chapter
Publication Acceptance Date: December 5, 2012
Publication Date: N/A

Technical Abstract: The fungus causing violet root rot, Helicobasidium brebissonii (anamorph Rhizoctonia crocorum), is widely distributed in Europe and North America but is rarely of much economic importance on alfalfa. The disease has also been reported in Australia, Argentina, and Iran. The disease is characterized by yellowed and dying plants in circular to irregular patches. Infected roots have a compact felt cloak of mycelium that is bright violet to cinnamon colored that often extends 20 cm or more below the soil line and is also abundant in the crown. As the root rots, its bark loosens and the central cylinder becomes soft and shredded. Minute black sclerotia just visible to the naked eye are often present on dying roots. The disease is most common after midsummer. Gramineous plants are highly resistant and can be grown safely where the disease is a problem.

Last Modified: 10/1/2014
Footer Content Back to Top of Page