Cool Conditions May Lead to White Mold in Soybeans

Cool Conditions May Lead to White Mold in Soybeans

Soybean stems with Sclerotinia;

Figure 1. A white, cottony fungal growth on soybean stems is one indication of Sclerotinia Stem Rot.

Most of Nebraska's soybean crop is flowering, ranging from the early to late stages of bloom. With this week's cool temperatures, conditions are right for white mold (Sclerotinia Stem Rot) to start the infection cycle. Those growers with fields with a history of this disease should be aware that it may be more severe this year with the current weather trend. General information on Sclerotinia Stem Rot of soybean can be found in a regional Extension publication or in the Plant Disease section of CropWatch at Schlerotinia Stem Rot

We do not typically see Sclerotina Stem Rot in Nebraska as temperatures during flowering are usually warmer than this year. Therefore, we do not have any consistent fungicide trial data to evaluate products. I recommend you look at the University of Wisconsin Fungicide Test Summary to compare treatments.

Application during bloom is critical if you're targeting Sclerotinia Stem Rot. If you're not targeting a specific soybean disease, applications are typically at the R3 stage for the added yield boost and crop health response.

Management for Sclerotinia Stem Rot is difficult, but fungicide sprays at flowering are the most effective timing if fungicides are used.  If you're considering a fungicide application to manage this disease, now is the time. Once flowers are infected, the disease will spread slowly, so stopping the initial infection is critical.

Loren Giesler
Extension Plant Pathologist

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A field of corn.