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Life cycle, symptoms, and control measures of sclerotinia stem rot of soybeans is discussed.
Sclerotinia stem rot of soybeans is caused by the fungus Sclerotinia sclerotiorum. This pathogen has an extremely wide host range and can affect more than 400 plant species, including oilseed, vegetable and forage legume crops. S. sclerotiorum has caused a disease known as white mold on dry edible beans in western Nebraska for 40 years, but it did not become a problem in soybeans until the 1990s. This fungal pathogen can be found on soybeans in Illinois, Iowa, Michigan, Ohio, Minnesota, Wisconsin, and North Dakota.
Stem rot outbreaks in soybeans recently have become more frequent in eastern Nebraska. In other states, outbreaks usually occur in fields which have previously been rotated with a susceptible crop such as sunflower, dry bean or potato. Cereals such as corn and wheat and other monocots are not hosts for this fungus, but weeds such as pigweed and wild sunflower can become infected. In Nebraska the current increase in disease severity can be explained by the recent cool, wet summers which favored disease development in susceptible crops and weeds, leaving more inoculum to infect the soybean crop. Continuous soybeans would enhance inoculum and subsequent infection.