By Scout Nelson
White mold, also called Sclerotinia stem rot, is a fungal disease that affects soybeans during the flowering stage. The disease is caused by the fungus Sclerotinia sclerotiorum, which survives in the soil as black structures called sclerotia. These structures can live for years and reappear in the same field areas every season.
Soybean plants are most vulnerable from R1 to R3 growth stages. White mold infection begins when the weather is wet and humid, especially in fields with a full canopy. Mushrooms called apothecia grow from the sclerotia and release spores that infect flowers and injured tissues. Once infected, plants may show wilting, brown stem lesions, and cotton-like fungal growth. Black sclerotia often form inside hollow, brittle stems.
To manage this disease, farmers should choose soybean varieties with resistance to white mold and avoid highly susceptible ones. Wider row spacing can help by reducing humidity in the plant canopy. If possible, farmers should avoid irrigation during flowering. Rotating soybeans with non-host crops like corn also reduces disease risk.
Maintaining healthy soil is important. Manganese levels in soil affect the plant’s ability to resist white mold. Applying foliar manganese before flowering may improve plant defence.
Fungicides work best if applied early during flowering when weather conditions support disease development. Late fungicide application will not help already infected plants. Farmers are advised to check the latest local crop protection guides for effective fungicide options.
White mold is common in areas with cool, wet weather, such as northern and central Nebraska. Early action is necessary to prevent losses.
Photo Credit: istock-ds70
Categories: Nebraska, Crops, Corn, Soybeans