Brown stem rot of soybean

Brown stem rot (BSR) is a destructive fungal disease of soybean caused by the soil-borne pathogen Cadophora gregata. The fungus invades the vascular tissue of the host plant, effectively blocking the translocation of essential nutrients and moisture, which leads to the collapse of the plant's hydraulic system.

The primary crop affected by this pathogen is soybean (Glycine max). The disease is distributed globally in major soybean-producing regions. Because the fungus survives in crop residues buried in the soil, it poses a recurring threat to fields where soybean is grown in frequent rotations.

Disease symptoms typically become visible during the mid-to-late stages of soybean development, often triggered by the onset of pod filling. The most diagnostic symptom is the internal browning of the stem pith. Foliar symptoms appear as interveinal chlorosis and necrosis, with leaves often remaining attached to the stems even after the plant has died.

The development of BSR is strongly influenced by environmental conditions, particularly cool, moist weather during the early vegetative stages. The pathogen enters the plant through the roots and progressively colonizes the xylem. Spread is facilitated by the movement of contaminated soil, infected seeds, and wind-blown or rain-splashed fungal spores.

Economic damage caused by brown stem rot includes significant yield loss, ranging from moderate reductions to total crop failure in highly susceptible varieties. To manage the disease, agronomists recommend a combination of strategies:

• Planting resistant or tolerant soybean cultivars as the most effective control method.
• Implementing long-term crop rotation (at least 3 years) with non-host crops like corn or wheat.
• Ensuring proper soil drainage to avoid moisture stress.
• Reducing soil compaction to promote healthy root growth.
• Applying adequate fertilizers to ensure balanced crop nutrition and vigor.