The pathogen persists in the soil as sclerotia, which can remain viable for up to 12 years. Infection occurs through two pathways: via soil-borne mycelium, which causes basal stem rot, and via ascospores, which are air-borne and typically infect the plant through the flowers.
Symptoms of the disease include the appearance of light-brown lesions on the stems, which become covered with white, cottony mycelial growth under high humidity conditions. Inside the infected stems, the pith is destroyed, turning into a decayed mass containing black sclerotia. When pods are affected, the valves lose color and disintegrate, leaving only the vascular strands, while the seeds may rot or become covered in mycelium.
No specific resistance genes have been identified in soybean; therefore, protection relies on the use of varieties with quantitative (polygenic) resistance. This trait is closely linked to plant architecture, particularly an open canopy type, which improves air circulation and reduces the likelihood of infection development.
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White mold.