By Scout Nelson
ool temperatures and consistent rainfall across Nebraska have created ideal conditions for white mold (Sclerotinia stem rot) to spread in 2025. The risk is highest in eastern and central parts of the state.
History is key. Fields that have had white mold before are the most likely to be affected again. The fungus survives in soil and tends to reappear in the same hot spots.
Timely fungicide application is still possible in soybean fields currently in the flowering stage (R1 to R3), but this critical window is closing fast.
“Preventative fungicide sprays are only effective before infection occurs — they won’t reverse established disease.”
Disease development has been fueled by two recent days of low temperatures that followed significant rain, especially in eastern Nebraska. Although short bursts of high temperatures may briefly slow the disease, favorable conditions are likely to return.
White mold begins when hardened sclerotia in the soil grow into small mushroom-like structures during moist, cool weather. These release spores that infect soybean flowers. Once infection starts, it cannot be reversed.
To manage effectively, focus on high-risk fields. Areas with a history of white mold may still benefit from fungicide applications. Fields without a history are less likely to see major diseases, even with widespread risk.
Other management strategies include:
- Genetic resistance: Use varieties rated against white mold.
- Cultural practices: Use wider row spacing, reduce irrigation during flowering, and rotate crops.
- Chemical/biological control: Apply recommended fungicides at the right stage in at-risk fields.
Proper disease identification is important. If unsure, send samples to the UNL Plant and Pest Diagnostic Clinic. Additional support is available through Nebraska Extension and the Crop Protection Network.
Photo Credit:pexels-ron-lach
Categories: Nebraska, Crops, Soybeans, Weather