Plant Health Initiative

Charcoal Rot - Scouting

Soybean plants damaged and killed by charcoal rot. Click on image to view a larger version. Photo credit: J.A. Wrather et al. Plant Management Network.

Symptoms in affected fields appear as individual plants or patches of wilted and dead plants. Charcoal rot symptoms can be evident in soybean plants of all ages.

Gray to black "specks" will be apparent on the lower stems of affected plants when the epidermis is scraped with a knife. These specks, known as microsclerotia, are the survival structures of M. phaseolina.

Hot, dry weather is optimal for charcoal rot development. Scout fields during these conditions.

Charcoal rot symptoms can be mistaken for brown stem rot (BSR) because both diseases are characterized by a discoloration in the pith. Look closely for evidence of mcirosclerotia to diagnose charcoal rot. Discoloration caused by BSR can occur higher in the stem than the discoloration caused by charcoal rot, which is more limited to the first few nodes.

The small, black microsclerotia produced on soybean roots, stems and pith are released into the soil as these tissues decay. Click on image to view a larger version. Photo credit: Chris Little, Kansas State Universi

References

Be on the Lookout for Charcoal Rot in Dry Areas. The Bulletin, University of Illinois. September 2011

Charcoal rot -- a dry weather disease. Integerated Crop Management. Iowa State University.