The most common hosts are the legumes, crucifers, and cucurbits. The fungus persists in many weed hosts as well. Following this, the fungus produces abundant white, fluffy mycelium on infected tissues and the soil. Mature sclerotia resemble mustard seed.
Seedlings are very susceptible and die quickly once they become infected.
Older plants that have formed woody tissue are gradually girdled by lesions and eventually die. Invaded tissues are pale brown and soft, but not watery. S. rolfsii grows, survives, and attacks plants at or near the soil line. Before the pathogen penetrates host tissue it produces a considerable mass of mycelium on the plant surface, a process which can take 2 to 10 days. Penetration of host tissue occurs when the pathogen produces an enzyme which deteriorates the hosts' outer cell layer.