Charcoal Rot of Soybean

Charcoal rot is caused by the soilborne fungus Macrophomina phaseolina. Initial symptoms of charcoal rot are patches of stunted or wilted plants. Leaves remain attached after plant death. The fungus produces numerous tiny, black fungal structures called microsclerotia that are scattered throughout the pith and on the surface of taproots and lower stems. These microsclerotia give the lower stem and taproots a discolored light gray or charcoal-like appearance. Although infection can occur very early in the season, symptoms usually appear after flowering. Charcoal rot is most yield-limiting when weather conditions are hot and dry. Stunted or wilted plants in patches are the initial symptoms of charcoal rot. Image: D. Mueller

Charcoal-like, gray discoloration from numerous microsclerotia characteristic of charcoal rot. Image: D. Mueller

Charcoal rot disease cycle.

The fungus survives in soil or soybean residue as microsclerotia. Growing small grains, such as wheat or barley, can reduce microsclerotia numbers. Because corn is a host, it will not reduce levels of the fungus when grown in rotation with soybeans. Fields with minimal or no tillage may have fewer symptoms because of lower soil temperatures and greater water-holding capacity. Avoid excessive seeding rates so that plants do not compete for moisture, which increases disease risk during a dry season. 

For more information see the Charcoal Rot publication. 

Gallery Images: D. Mueller, C. Bradley, M. Chilvers, T. Mueller, and A. Robertson

Related Publications

An Overview of Charcoal Rot of Soybean

Related Articles

Taproot Decline of Soybean

Taproot decline (TRD) of soybean was fir...

Anthracnose Stem Blight of Soybean

Anthracnose stem blight is generally a l...

Thielaviopsis Root Rot of Soybean

Thielaviopsis root rot, also called blac...

Other Nematodes of Soybean (Sting, Lesion, Reniform, and Lance)

Many species of nematodes that feed on s...

Stem Canker of Soybean

The first symptoms of stem canker are of...