Agronomic Bulletin


Sudden Death Syndrome

Sudden Death Syndrome (SDS) is a fungal disease. The fungus is soil borne and infections occur early in the plant’s development, in the vegetative stage. We don’t observe the symptoms however, until reproductive stages of growth, usually after the R2 stage. There are no completely resistant cultivars, but there are levels of partial resistance. Partial resistance is inherited from multiple genes with varying levels of susceptibility among cultivars. Historically, SDS was thought of as a problem in river bottom fields or at least in highly fertile fields with high yield potential.

Symptoms of SDS include: Yellow, interveinal leaf chlorosis usually after the R2 plant growth stage. (1) Symptoms may occur before flowering in severe cases but they are more pronounced later. The soybean leaflets turn brown and fall off, leaving only petioles. The cortex of the lower stem has brown or gray streaks, but the pith is normal. (Purdue Corn & Soybean Field Guide, ID-179) The fungal pathogen that causes SDS is Fusarium virguliforme. (2)

This disease was first identified in southern states but it has been identified in recent years in northern Illinois, Iowa & Minnesota. It can occur in oval to circular patches within a field or in severe cases the majority of a field will exhibit symptoms. Some factors that favor disease development of SDS are years with high levels of soil moisture with cooler temperatures.

The key for infection is the weather pattern that occurs in the early vegetative growth stage. Periods of wet weather, especially saturated soils during early vegetative growth are correlated with a higher incidence of SDS. In years with dry weather patterns until flowering, symptoms of SDS will rarely be seen. Fields with higher levels of soybean cyst nematode will also contribute to the severity of the foliar symptoms.

Click this thumbnail to see the full size picture of a field with severe Sudden Death Syndrome. Notice how the leaf has fallen off the petiole.

Management Options

  • Plant soybean varieties with good tolerance ratings for SDS and/or that have performed well where SDS has been a problem.
  • Improve drainage in poorly drained fields & avoid compacting soils
  • Delay planting until the soil is warm & dry. Fields with a history of SDS problems should be planted later, when that is an option
  • Rotate crops; especially avoid continuous soybeans
  • Manage toward reducing soybeans cyst nematode populations
  • Maintain a good fertility program to reduce the severity or incidence of SDS

Credits
  1. Purdue “Corn & Soybean Field Guide”, ID-179, 2009 edition
  2. University of Missouri “Soybean Diseases”, IPM1002, 2008
  3. The Ohio State University, Extension Fact Sheet, AC-44-98
  4. Pictures courtesy of Iowa State University

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