Sudden Death Syndrome

SDS: Finding solutions for farmers Update for 2010 NCSRP has put together a new 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)»

Sudden death syndrome (SDS) is a 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 significantly. Yield losses due to SDS range from slight to 100%, depending on the soybean variety.

There’s a lot going on with sudden death syndrome (SDS), now one of the top four yield-robbing diseases in soybean and spreading fast. On the positive side, scientists are breeding varieties with better resistance, and learning more about how and when SDS infects soybean plants.

Critical infection stage is soon after planting

New research suggests that the critical stage for the SDS pathogen to infect soybean plants is before emergence of the germinated seed. Infections occurring at early growth stages are more likely to produce foliar symptoms late in the summer. Soybeans planted early in cool soil have slow germination and emergence, which prolongs the contact period between pathogen and soybean, promoting infection.

SDS spreads with the movement of soil, and in association with soybean cyst nematode

SDS is caused by a soil-borne fungus that is spread mainly with the movement of soil on equipment, human and animal feet, birds, and wind and water erosion. SDS is found commonly 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.

The SDS pathogen

Sudden death syndrome is caused by the soil fungus, Fusarium virguliforme. The fungus produces a toxin that is translocated throughout the plant and interferes with the vascular system of the plant. This can cause sudden yellowing and death of the leaves as the water supply is cut off. The pathogen also causes a root rot.

Root rot occurs on plants infected with the SDS pathogen. A blue discoloration is visible on this infected root. Click on image to view a larger version. Photo credit: X.B. Yang, Iowa State University

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, due to the large number of conidia (spores) produced on the surface.

The fungus also produces a thick-walled survival structure, called chlamydospores, in the cortical tissue of soybean roots. The chlamydospore can overwinter and can survive for several years in the soil.

The SDS pathogen is very closely related to another soybean pathogen that causes seedling disease and root rot of soybean, Fusarium solani form B.