Fighting White Mold in Soybeans Through Vigilance and Research

August 9, 2023

Recent rains have brought much-needed moisture to soybean farmers, but at the same time, raised concerns about increased disease pressure. White mold is one such disease which has long been a concern for soybean producers, not only in South Dakota but across many soybean-growing regions.

The white mold disease-causing fungal pathogen Sclerotinia sclerotiorum, thrives in cooler, moist conditions. The rain in the past few weeks, especially after the canopy closed has created favorable conditions for white mold development. Initial symptoms typically develop from R3 to R6 growth stages. Farmers might observe a white, cottony growth on the lower stem nodes (Figure 1a). As the disease progresses, it can spread to other parts of the plant, including pods and seeds, leading to wilting, lodging, and even plant death.

The fungus produces hard, black, resting structures known as sclerotia (Figure 1b). These sclerotia resemble rat droppings and fairly hard structures (Figure 1) and can survive in the soil for many years. They may also be found mixed with the seeds. Regular scouting, early detection of white mold (Figure 1c), and research on pathogen diversity can help mitigate its impact on the varieties grown in the state.

If you notice white mold symptoms in your fields, please consider contacting SDSU pathologists to collect pathogen samples, field survey, share sclerotia mixed seeds to aid in research, which can lead to better prevention and treatment methods in the future. Your vigilance and collaboration can make a significant difference in our collective fight against white mold.

Contact information:

Dr. Shyam Solanki

Plant Pathologist, SDSU

251 Berg Hall


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