What to look for when scouting for sudden death syndrome in soybean fields

Sudden death syndrome can impact yields significantly if left unnoticed. Know what symptoms to look for when scouting your soybean fields for SDS.

Soybean sudden death syndrome (SDS) is beginning to show symptoms in some irrigated soybean fields in southwest Michigan. Most of the fields where I have seen SDS in 2011 are irrigated sandy fields with high yield potential. While the more severe symptoms are easy to spot in fields, the initial leaf symptoms can be subtle, making the disease hard to identify. The patterns of infection often seem to coincide with pockets of high soybean cyst nematode (SCN) activity in the fields. Often, the infected plants also look to be stunted in growth. The initial leaf symptoms are yellow spots on the leaves. These yellow spots begin to coalesce into a more significant yellowing pattern with time.

Progressing disease symptoms
The leftmost leaf is non-infected. Continuing to the right is a progression of SDS
symptoms, leading to the rightmost leaf that is severely infected.
To see a larger version of the image, click here.

Finally, the more easily identifiable interveinal yellowing with brown necrosis begins to become visible on the more severely infected plants (See below photo).

Leaves with SDS symptoms 

When scouting, look for areas within fields that are exhibiting premature drying and appear a “crispy” brownish-yellow color. These areas often appear as though the plants are being severely impacted by drought. In heavier-textured soils or where soybean cyst nematodes are not a significant problem, areas that have been stressed by excess moisture, compaction or drought often are where SDS symptoms first occur in fields.

Infected leaves
Click here to view larger version of image.

Sudden death syndrome can impact yields significantly, especially when the leaf symptoms begin to occur early in the growing season. In looking at the MSU Variety Trial and Research Plots at the SDS Research Center near Decatur, Mich., this season, there are tremendous differences between varieties in their ability to tolerate SDS infection. Read previous MSU Extension article Sudden death syndrome beginning to show symptoms in southwest Michigan soybean fields to learn more about SDS.

Differences in plant height
Plant height differences of a more SDS-tolerant variety (background) compared
to a more SDS-susceptible variety (foreground) at the MSU Southern Michigan
Soybean Disease center SDS Research Trial in 2011.

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