Infections occur anywhere along the tap root, but lesions tend to be more abundant on the upper third of the root and are often found where lateral roots emerge from the taproot.
Lesions begin as pinpoint, sunken spots and generally enlarge as roots mature.
Pythium violae also causes lesions on alfalfa roots. Infections of other hosts such as celery, blackeye beans, wheat, cucumber, and beets may not result in symptoms. Nonhosts include tomato, cotton, watermelon, corn, and potato. Practice 3-year crop rotations with crops other than alfalfa or carrots. Do not overirrigate.