Soybean Disease Overview
For some diseases, there are in-season management strategies that can help, and unfortunately, for others, there is not much that can be done. Below is an overview of key soybean diseases to monitor in season.
- Sclerotinia Stem Rot (White Mold): Estimated $ lost over the last 2 seasons in NE was $51,702,788
(Credit Tristan Mueller, InnerPlant)
White Mold, caused by Sclerotinia sclerotiorum, is responsible for the most yield loss by a fungal pathogen over the last two years in Nebraska. The fungus typically infects the plants through the senescing flowers and symptoms will show up in July and August. The plants will start to turn gray and brown, white fluffy mycelium will start growing, and eventually, the sclerotia will form.
The good news with white mold is that there are options for controlling this disease during the season. A well-timed fungicide spray with efficacious active ingredients can be effective. Also, avoiding watering during flowering can help. If you have fields that are at risk of white mold, you should avoid planting narrow row soybeans.
- Sudden Death Syndrome (SDS): Estimated $ lost over the last 2 seasons in NE was $46,847,570
(Credit Tristan Mueller, InnerPlant)
SDS, caused by Fusarium virguliforme, is a significant concern in Nebraska. Symptoms typically appear in mid to late July, characterized by interveinal chlorosis and necrosis on leaves. The disease thrives in cool, wet soils and is exacerbated by the presence of Soybean Cyst Nematode (SCN).
Currently, there is no known control of SDS in-season, but in fields with a history of disease outbreaks seed treatments can be applied, avoid early planting, and more resistant varieties can be planted.
- Phytophthora Root and Stem Rot: Estimated $ lost over the last 2 seasons in NE was $29,610,161
(Credit Dylan Mangel-UNL)
Cool, wet soils favor seedling diseases like Phytophthora. Symptoms include seed decay, preemergent seedling rot, and seedling damping-off. the stem rot phase is easily identified by the dark brown color on the exterior surface of the stem and lower branches.
Selecting resistant varieties, using fungicide seed treatments, and improving drainage and soil health can help mitigate these issues.
- Brown Stem Rot (BSR): Estimated $ lost over the last 2 seasons in NE was $5,921,403
(Credit Tristan Mueller, InnerPlant)
Caused by Cadophora gregata, BSR leads to browning inside the stems and interveinal chlorosis on leaves. Symptoms are more apparent during the reproductive stages. Foliar symptoms are often mistaken for SDS, so it is important to split the stem to diagnose.
Management involves rotating out of soybeans, selecting resistant varieties, and improving drainage and soil health.
SOURCES:
Disease loss estimates are from the Crop Protection Network Soybean Disease Loss Calculator.
Cropwatch was also used to source some disease information.
https://cropwatch.unl.edu/plant-disease/soybean/