In the most common form of germination, a sclerotium produces one or more dark germ tubes, or stipes, that grow upward from a depth of two inches or less in the soil. When it reaches the soil surface, the germ tube is triggered by light to produce a small, flesh-colored structure much like a mushroom, called an apothecium. One sclerotium can produce numerous apothecia simultaneously or sequentially throughout the growing season. Each apothecium produces millions of spores beneath the plant canopy, which are periodically released and spread to the plants. Spores are not able to invade plants directly, but rather, must colonize dead plant tissue before moving into the plant.
Dead flowers provide a ready source of tissue for preliminary colonization.
The fungus then spreads from these flowers to healthy tissue. Plant damage is incurred as tissue rot and formation of sclerotia inside the stem result in rapid wilting and death of the upper part of the plant. As the disease progresses, premature death of the entire plant can occur. Management and environmental conditions that enhance the occurrence of white mold Sclerotia germinate under high soil moisture and cool temperatures. After establishment, the disease flourishes in cool, humid conditions, which are more prevalent with narrow rows, high residue, high populations, or good stands with dense canopies and in soybeans under irrigation.