Sudden Death Syndrome

Over 80 people attended the 15th annual Sudden Death Syndrome (SDS) Fall Meeting in St. Paul. View the summary and presentations» Researchers reported that the 2011 SDS Regional Variety Trial was one of the largest trials ever conducted.

Leaf symptoms and root rot on soybean infected with sudden death syndrome. Photo credit: Dean Malvick.

Sudden death syndrome (SDS) is a late-season soybean disease characterized by leaf spots and root decay. The name sudden death syndrome is descriptive in that normal-appearing plants turn yellow and die rather quickly. The disease is of major concern because of its potential ability to reduce yields — from a slight yield loss to 100%, depending on the soybean variety. SDS is now considered one of the top four yield-robbing diseases in soybean.

Infections occurring at the seedling stage produce symptoms late in the summer

New research suggests that the critical stage for the SDS pathogen to infect soybean plants is before emergence of the germinated seed. Soybeans planted early in cool soil are susceptible to SDS infection when slow germination and emergence prolongs the contact period between pathogen and soybean. Although infection has occured, no symptoms are generally seen until the early reproductive stages..

The SDS pathogen

Sudden death syndrome is caused by the soil fungus, Fusarium virguliforme. The fungus is closely related to another soybean pathogen, Fusarium solani form B, that causes seedling disease and root rot of soybean.

The SDS pathogen produces a toxin that is translocated throughout the plant and interferes with the vascular system of the plant. Sudden yellowing and death of the leaves occurs as the water supply is cut off. The pathogen also causes a root rot.

Fusarium virguliforme has a blue pigmentation, and a blue coloration is sometimes found on the tap roots of plants that are severely infected with the pathogen. The coloration is due to the large number of conidia (spores) produced on the root surface.

SDS: Finding solutions for farmers NCSRP has put together a 12-page report on SDS, packed with current research-based information about this complex disease and how to manage it. Order your free print copy by calling 1-800-383-1423 (orders for mailing within the U.S. only, please), or read online (pdf)»

The fungus also produces thick-walled survival structures called chlamydospores in soybean root tissue. Chlamydospores can survive for several years in the soil.

SDS is commonly associated with the soybean cyst nematode

The SDS pathogen spreads from field to field with the movement of soil on equipment, field activity, birds, animals, and wind or water erosion. SDS is also found in the cysts of soybean cyst nematode (SCN) , and is likely spreading north with the movement of SCN. Because of this close association with between SDS and SCN, assume that if you have one or the other, you probably have both. Test for SCN and make management decisions based on both.