Plant Health Initiative

Sudden Death Syndrome - Symptoms

Figure 1. Scattered yellow spots are the early leaf symptoms of SDS

Figure 2. Late-season foliar symptoms of SDS Photo credit: Dean Malvick, University of Minnesota

Figure 3. Root rot occurs on plants infected with the SDS pathogen. This symptoms distinguishes SDS from brown stem rot and stem canker. Note blue discoloration on this sample. Click on image to view a larger version. Photo credit: X.B. Yang, Iowa State University

Symptoms of SDS are fairly easy to recognize. SDS begins as small, bright, pale green to yellow circular spots on the leaves during late vegetative or early reproductive growth stages (Figure 1).

As the disease progresses, the tissue in these spots starts to die and enlarges to form brown streaks between the veins (Figure 2). Symptoms are more pronounced on top leaves. Flowers and pods may abort or not fill.

Root rot symptoms

Another key symptom of SDS is substantial amounts of root decay and discoloration of roots and crown (Figure 3). Diseased plants are easily pulled out of the ground because the taproots and lateral rots have deteriorated. Symptoms present on both the leaves and roots is diagnostic for SDS.

Look-alikes

SDS may be mistaken for brown stem rot (BSR) and stem canker because these diseases show similar leaf symptoms. It is important for growers and crop advisors to be able to distinguish between these diseases because the control measures are different.

SDS has symptoms on both leaves and roots. The outer tissue of SDS- infected stems can be rotted, but the stem’s pith remains white. Brown stem rot infection does not result in root rot, and infected plants have a distinct brown center (pith). Stem canker results in a brown canker on the main stem and stems become brittle. Stem canker is not associated with root rot.

If you suspect SDS, send whole infected soybean plants (tops and roots) to a plant disease clinic for identification.