Sudden death syndrome (SDS) is a soilborne disease of soybeans caused by the fungus Fusarium virguliforme. This disease infects soybeans during the seedling stage during prolonged periods of cool, moist weather, resulting in root rot. Rains at the reproductive stage of growth cause the fungus to deeply colonize the roots and produce a toxin, resulting in the characteristic interveinal necrosis.
A leaf with interveinal chlorosis characteristic of SDS
If you are lucky, you will see blue growth around the soil line, which is indicative of SDS.
Blue growth (within circle) on the roots or soil line indicates the presence of SDS.
SDS has become a yield-limiting disease in high input fields in the Midwest, and is present at low levels in the mid-Atlantic. Glyphosate-resistant soybeans are commonly planted because they facilitate weed management. Over 90% of soybeans planted in the United States contain glyphosate resistance. There have been reports of glyphosate related issues with diseases in soybeans, including SDS, with some studies showing an increase in disease, and others indicating a reduction of disease when glyphosate is used.
A paper recently published in Plant Disease examined the effects of glyphosate on SDS severity, grain yield, and plant nutrition in studies conducted across five states in the US and one site in Ontario, Canada from 2011-2013. What did they find? There were no effects of herbicide on disease, and treatments with glyphosate tended to yield more than treatments with non-glyphosate containing herbicides. In addition, there were no effects of glyphosate on plant nutrition.