Charcoal Rot

Tiny dark fungal structures on stem, pith and root tissue look like charcoal dust. Click on image to view a larger version. Photo credit: Chris Little, Kansas State University

Early death due to charcoal rot infection during drought conditions Click on image to view a larger version. Photo credit: Chris Little, Kansas State University.

Charcoal rot is a root disease caused by the soil fungus Macrophomina phaseolina.

The fungus causes a general root rot in soybean, infecting the roots and lower stems. It was named from the fact that infected tissues look as if they have been dipped in charcoal dust.

Although the initial infection occurs in the spring when soil moisture is high, symptoms of charcoal rot develop in the hottest, driest part of the growing season.

The pathogen is extensively distributed in soils worldwide. In the U.S., it is more prevalent in southern states, but can occur anywhere when hot, dry conditions prevail.

The pathogen can infect over 500 different kinds of plants, including important agronomic crops such as soybean, corn, grain sorghum, sunflowers and alfalfa.