Early Season Soybean Diseases
BY Dairyland Seed Agronomy Team
As soybeans continue to emerge across the Dairyland Seed footprint, there are several early season, yield and income robbing diseases that often appear in our area. The most common of these diseases are phytophthora, pythium, and rhizoctonia. Properly identifying these diseases now can help us manage them in the future.
Phytophthora
Phytophthora is a soilborne disease that can impact soybeans at any growth stage, but early season infection is common once soil temperatures reach 60 degrees F and soils become saturated. Phytophthora-infected seedlings will have brown/black and shriveled hypocotyls (necks) and discolored cotyledons, but the roots will often be intact. As the soybean plants mature into VC and through vegetative growth, brown lesions can be found on the stem at the soil line and extend from the tap root. When the area affected by the lesion is split, the cortex and pith of the root and stem will be brown and often water soaked.
Pythium
Pythium, also a soilborne disease, often appears in the north when planting conditions are cool, soil temperatures between 50- and 60-degrees F, and soils are wet. We often refer to pythium as “dampening off.” Seedlings will often emerge, and the hypocotyl and cotyledons will be brown and soft, and the young plant can be pulled from the soil easily due to a rotten root system. Dampening off will most often occur in a similar environment to phytophthora, saturated soils in low areas or areas where crusting seals in the soybean in a saturated environment.
Dean Mavlick.” Soybean seed and seedling diseases. University of Minnesota Extension, University of Minnesota, https://extension.umn.edu/pest-management/soybean-seed-and-seedling-diseases. Accessed 6 June. 2021.
Rhizoctonia
Rhizoctonia is a very common early season, soilborne disease in the Dairyland Seed footprint. Impacted plants will occur in singles or small groups in a field, most often on light or sandy slopes. The identifying characteristic of rhizoctonia is a sunken, reddish-brown lesion on the soybean seedling hypocotyl and, in more mature soybean plants, the lesion can be found on the stem at the soil line. The lesion of rhizoctonia will remain in the epidermis or outer layer of the stem tissue. When the plant is split, the tissue inside the plant will be white and healthy.
Dean Mavlick. “Rhizoctonia Root and Stem Rot on Soybean.” University of Minnesota Extension, University of Minnesota, https://extension.umn.edu/pest-management/rhizoctonia-root-and-stem-rot-soybean. Accessed 6 June. 2021.
Environmental factors that are out of our control impact early soybean disease infection, but we do have tools to help give us the best chance possible. Seed treatments, proper variety selection and placement are our best defense against these early season issues. If you have further questions, contact your local Dairyland Seed District Sales Manager or Regional Agronomist.
Brian Weller
Western Region
507.456.3034
Rod Moran
Western Region
507.456.3034
Dan Ritter
Central Region
219.863.0583
Branden Furseth
Northern Region
608.513.4265
Mark Gibson
Eastern Region
260.330.8968
Amanda Goffnett
Eastern Region
989.400.3793
Ryan Mueller
Eastern Region
989.400.3793