DISEASES OF ALFALFA - CROWN ROT

Of the pathogens mentioned previously, Phoma medicaginis, cause of Phoma crown rot (shown in this photo), has received the greatest attention. P. medicaginis not only causes crown rot, but also causes an alfalfa stem and leaf disorder called Spring black stem. Initial infections by the fungus are thought to occur aboveground, then spores produced in these infected areas wash into the crown leading to the crown rot phase of the disease. Decay proceeds down the crown and into the root system.