Sudden Death Syndrome

Leaf symptoms of sudden death syndrome. Photo credit: Dean Malvick, University of Minnesota

Sudden death syndrome (SDS) is a soybean disease causing leaf spots and root decay. The disease is of major concern because of its potential ability to reduce yields significantly.

Sudden death syndrome is caused by the soil fungus, Fusarium solani f. sp. glycines. Root infection can occur very early in the growing season, within 2 to 3 weeks after planting. 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.

How SDS spreads

SDS is a soil borne disease and is spread mainly when soil is spread: equipment, human and animal feet, birds, and wind and water erosion. Cysts of soybean cyst nematode have been found to carry the SDS fungus.

The pathogen

SDS is caused by blue-pigmented strains of Fusarium solani f. sp. glycines. This blue coloration is sometimes found on the tap roots of plants that are severely infected with F. solani f. sp. glycines due to the large number of conidia (spores) produced on the surface. This fungus also produces a thick-walled survival structure, a chlamydospore, in the cortical tissue of soybean roots. The chlamydospore can overwinter and can possibly survive for several years in the soil. This fungus is very closely related to another soybean pathogen that causes seedling disease and root rot of soybean, Fusarium solani form B.

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