Sudden Death Syndrome Developing In Soybeans

 

Sudden death syndrome (SDS) was found in two fields in Minnehaha County and one field in Miner County. One field in Minnehaha had moderate symptoms in a small section of the field (Figure 1), while the other fields had very few scattered plants with SDS symptoms.

 

 

Sudden death syndrome is fungal disease caused by Fusarium virguliforme. This pathogen survives in infested soybean residue and soil for several years. Infection is promoted by planting in wet, cool soils in spring. The SDS pathogen infects soybean seedlings early in the growing season but symptoms appear and develop at the early reproductive stages under cool temperatures and frequent rainfall.

 

 

SDS symptoms start as small chlorotic spots on leaves. These quickly expand leading to large yellow blotches that eventually become necrotic (dead) between the leaf veins, leaving green veins (Figure 2). Infected plants have rotted roots and splitting the stem lengthwise reveals the browned cortex and white pith.

 

To distinguish SDS from other root and stem rots such as brown stem rot, Phytophthora root and stem rot and others, split the stem and look for the discolored cortex near the tap root as well as white pith. Brown stem rot does not cause root rot and the pith is brown, while Phytophthora root rot causes a dark brown lesion that starts from the tap root and continues up the stem above the soil line.

 

 

 

There are no in-field treatments for SDS. Since the SDS pathogen infects soybeans at planting, managing SDS should begin before planting. SDS is favored by planting in cool wet soils in spring. Therefore plant when soils are warm and not excessively wet. Some fungicide seed treatments are effective at protecting seedlings from infection. The active ingredient fluopyram has been tested and found to be effective against SDS. See the 2016 Soybean Pest Management Guide for other soybean seed treatment products.