Plant death quickly proceeds across a field. Acremonium causes corky bands on primary and secondary roots.
Infected roots are straw colored or slightly darker than healthy roots.
Rhizopycnis causes a reddish tinge to the upper tap root. Infected tissue may be corky. All pathogens are soilborne. The disease usually occurs just before harvest, and the foliage and roots in affected fields may appear healthy for the majority of the season. The disease is unpredictable.