Source: University of Missouri
This is the time of year when late season soybean diseases may show up in Missouri soybean fields. Symptoms of late season Phytophthora root rot, sudden death syndrome (SDS) and Cercospora leaf spot/blight might be evident in fields. In addition to Phytophthora, SDS and Cercospora, Septoria brown spot has moved up in the canopy of some fields. This is also the time of year when anthracnose and pod and stem blight may show up on maturing soybean plants. Losses from soybean cyst nematode continue to be a problem. This would be a good year to sample fields for SCN. In areas of the state which have experienced recent hot, dry conditions, charcoal rot could become a problem.
Yield losses from these various late season diseases will vary depending on when symptoms began to occur, number of plants infected, severity of disease in infected plants and weather conditions from now to harvest. In some cases although yellowing of the upper nodes may be quite widespread and spectacular in a field, damage is limited to the uppermost leaves and pods so yield loss should be minimal. In other cases, especially with sudden death syndrome, the entire plant may have been killed prematurely. If large areas of a field are thus affected, yield losses will be greater. Although it is too late in the season to do much to control these diseases this year, there are some management strategies to prevent or minimize these diseases next season.