Sclerotia are spherical, tan or brown in color, and about the size of a mustard seed. Soybean is generally tolerant to this disease and economic losses are rare in North Carolina. Charcoal Rot Macrophomina phaseolina is a fungus which is widely distributed in soils and may be either seedborne or soilborne. This fungus attacks a wide variety of plants, including cornsoybean, cotton, grain sorghum, and numerous weeds. It can attack soybean plants at any stage of development, but is most evident following periods of hot, dry weather.
Infected plants have smaller leaves and grow slowly.
Leaves of older plants turn yellow and wilt, but remain attached to the plant. A grayish or silvery discoloration of tissue under the bark of the upper tap root and lower stem are symptomatic on older plants. The distribution of infected plants may be scattered or uniform. This disease should be suspected if previous corn crops were also poor. The key to managing this disease is alleviation of plant stress.