|MALVICK, DEAN - UNIVERSITY OF MINNESOTA|
|Samac, Deborah - Debby|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/10/2017
Publication Date: 2/1/2023
Citation: Malvick, D.K., Samac, D.A. 2023. Diseases of alfalfa (Medicago sativa L.). In: Hollier, C. A., Padgett, G. B. and Draper, M. A., editors. Diseases of Field Crops. St. Paul, Minnesota: APS Press. p. 9-23.
Technical Abstract: Many different factors influence establishment and productivity of alfalfa stands, and diseases are often very important. Diseases of alfalfa result from the interactions between susceptible alfalfa varieties, pathogens, a conducive environment, and improper crop management practices. Alfalfa diseases can reduce yields, reduce forage quality, thin or destroy stands, decrease stand persistence, and increase susceptibility to winterkill, other diseases, and environmental stresses. The major seedling diseases of alfalfa are: Aphanomyces root rot, Phytophthora root rot, and Pythium seed rot and damping off. Both Aphanomyces root rot and Phytophthora root rot can affect mature plants. Major diseases principally occurring on crowns and roots are: bacterial wilt, Fusarium wilt, Verticillium wilt, and crown rot complex. Root-knot nematodes and root-lesion nematodes cause serious damage in some locations. Brown root rot and Phymatotrichopsis root rot are major diseases in locations where the pathogens occur. The major diseases that occur on lower stems and crowns are: anthracnose, Rhizoctonia crown and bud rot, stem canker, and foliage blight, and Sclerotinia crown and stem rot. The major foliar diseases are: alfalfa mosaic, common leaf spot, downy mildew, Leptosphaerulina leaf spot, rust, spring black stem and leaf spot, Stemphylium leaf spot, and summer black stem and leaf spot. The stem nematode is a serious pest in western states causing stunting of alfalfa stems. This chapter provides information on disease symptoms, pathogen characteristics, and disease management practices for the major diseases of alfalfa that occur in the U.S.