Source: University of Illinois
Symptoms of charcoal rot, caused by the soilborne fungus Macrophomina phaseolina, are beginning to appear in dry areas of southern Illinois. Symptoms in affected fields appear as individual plants or patches of wilted and dead plants.
In affected plants, gray to black "specks" will be apparent on the lower stem when the epidermis is shaved off with a knife. These "specks" are the survival structures of Macrophomina known as microsclerotia. Charcoal rot thrives in hot and dry weather, and it may exist in other areas of the state where these conditions prevail.