White mold White mold is caused by the fungus Sclerotinia sclerotiorum. In most cases the sclerotia will form inside the stems of diseased plants. The sclerotia remain in the soil until they germinate and produce small fruiting structures, which look like small tan colored mushrooms. The fruiting bodies in turn produce spores, which are carried by the wind and infect the soybean plant through its flowers. Once established, the fungus invades the developing pod, node, and stem.
Infected plants have lesions with white cottony growth near the base of the stem.
This leads to wilting and death of the upper leaves and finally premature death of the infected plant. The development of the disease requires wet cool conditions during flowering. The sclerotia germinate to produce fruiting bodies after 7 to 14 days of high soil moisture. Once spores are released from the fruiting bodies, a wet surface for 12 to 16 hours recurring daily or a continuous wet surface for 42 to 72 hours is required for infection. Temperatures below 85 degrees favor disease development.