Most damage to soybeans results from infection by AG-4. Conditions which promote continued wet soils promote Rhizoctonia damage. Sudden Death Syndrome emerged in the South and Midwest during the 1980's. The pathogen causes a premature dying of plants at midseason. Disease has been associated with highly productive fields which undergo sudden heavy rainfall which floods fields for at least a day.
Infection occurs through roots.
Pathogen particular biotypes of Fusarium solani which produce characteristic blue pigments when grown in culture. Koch's postulates have been fulfilled. Symptoms gradually developing interveinal chlorosis proceeding to necros is upper roots and lower stem cortical tissues have a greyish-blue case pith remains white, distinguishing this disease from brown stem rot. It is known, however, that disease is favored by conservation tillag e, cool, wet weather or irrigation.