Sudden death syndrome plays by its own rules

Soybean Corner: When and where SDS shows up can be difficult to predict.
Jul 04, 2019
We’ve had issues with sudden death syndrome before. If it’s going to show up, where will I most likely see it? How can I determine if it will impact yield? What can I do if I find it?
The Indiana certified crop adviser panel answering this question includes Jamie Bultemeier, A&L Great Lakes Labs, Fort Wayne; Troy Jenkins, agronomist with Ceres Solutions, Rochester; and Marty Park, Great Lakes Seed Service, Rensselaer.
Bultemeier: SDS is most likely going to show up in continuous soybean fields. The more frequently soybeans are planted, the greater the chances of seeing SDS, since it resides in soybean residue. Cold, wet springs like 2019 increase severity of the infection. SDS tends to appear in areas that remain wet due to poor drainage and in compacted areas. These areas often coincide in the same parts of the field.
Impact on yield is very difficult to predict, as the severity of the infection in often weather-dependent. There’s no curative action once the disease appears. Management is focused on planting varieties that express SDS resistance and practicing crop rotation.
Jenkins: SDS fungi overwinter in plant residue, and infect and grow in soybean roots within days of planting. Brought on by wet and cold soil conditions, this disease becomes worse on tight or compacted soils. It’s also believed soybean cyst nematode can increase SDS severity due to weakened, disease- susceptible roots.
After infection, early-season root deterioration occurs, and the growing disease sends a toxin through the plant, causing leaflets to die and fall off the petioles after flowering. High rain events around flowering increase the incidence of leaf drop. The petioles remain on the soybean plant like sticks.
Depending on the year, it’s hard to know if or when SDS will show up. If it’s seen later in the season, nothing can be done to combat the disease at that time. Depending on infection, yield reductions can vary from minimal to almost 100%.
The use of resistant varieties is the best method of control. Other ways to reduce incidence is eliminate soil compaction, wait until soils are warmer and drier to plant, use new seed treatment fungicides to help control infection, and reduce nematode populations.
signs of sudden death syndrome on soybean leaves
Steve Gauck, Beck’s [signs of sudden death syndrome on soybean leaves]
WATCH FOR SYMPTOMS: Be on the lookout for symptoms of SDS. The infection occurs when beans are small, although symptoms appear later in the year.
Park: Sudden death is most likely to show up in early-planted soybeans in poorly drained, compacted areas. Be sure to check fields that have had a history of sudden death in the past. Yield impact can vary quite a bit from this disease. Some years it shows up in isolated spots of the field, while other years it just seems to take out large areas depending upon the tolerance in the soybean variety and the weather. 
Unfortunately, there is no “cure” for sudden death once you see it. The next time you raise soybeans in the problem field, make sure you choose a soybean variety with good tolerance to sudden death, use a seed treatment such as Ilevo, and delay planting that field until the soil is warm and dry.