|Brown stem rot|
No brown stem rot has been spotted yet, as it usually shows up after SDS; however, split the stem and check to see if the center of the stem is dark. If the center of the stem is brown, it is brown stem rot.
|Rhizoctonia root rot|
Even root rots, often found earlier in the season, can cause leaves to have similar foliar symptoms to SDS. The soybean symptoms above are foliar symptoms and reddish cankers on the base of the plant caused by Rhizoctonia.
|Rhizoctonia root rot|
We have not spotted any stem canker on soybean yet, but it too can be confused with SDS. Check the stem of the plant for cankers with tiny, dark specks (signs of the fungus) near stem nodes and at the base of the plant.
Here are the first signs of SDS foliar symptoms showing on soybean leaves. Symptoms will begin to appear after a heavy rain, when the fungal toxin of this disease is carried up the vascular system of the plant to the leaves.
Foliar symptoms of SDS. Picture taken by
Austin Kocher, Burrus Intern
There are no foliar fungicides that can be used as rescue treatments for SDS. The SDS pathogen favors soils that are cooler, compacted, or not as easily drained. Depending on soil types, compaction can be reduce by practicing no-till, because there are less passes over the field with equipment. On the other hand, significant tillage can also help to break up field compaction and allow vertical drainage to occur. Improving soil drainage and eliminating compaction will also help to reduce risk of the onset of SDS.
Ultimately, soybean yield loss will depend on SDS onset and severity. SDS is usually more severe when symptoms appear before soybean podfill. When symptoms occur this early, yield loss occurs by way of reduced seed number, because flowers and pods can be aborted. Unfortunately, SDS symptoms can become more severe over time, and soybeans stressed by SDS can be more vulnerable to other root, stem, and seed diseases. Soybeans that show symptoms after podfill can suffer yield loss due to reduced seed size, reduced pods, and seed weight, because seed quality could be at risk. As soybeans reach the later growth stages, such as R6, the final yield loss can be observed.
For now, if soybeans are showing SDS symptoms, we can focus on future disease management. Many, like Burrus/Hughes are evaluating the new ILeVO seed treatment in soybean side by sides across the country. More information on the observations and soybean yield results of the Burrus/Hughes PS SDS (PowerShield seed treatment with ILeVO) will be coming in the future. Some consider planting soybeans later into warm, dry soils to help reduce SDS risk; however, if you need to plant early, consider using PS SDS treated soybeans. All soybeans are susceptible to SDS, but, planting soybeans with higher level of resistance to SDS and SCN will also prove to be helpful. A rotation from soybean to corn will not help to combat SDS, because the fungal pathogen that causes SDS has also been found to survive on corn roots.