Brown Stem Rot

Brown stem rot (BSR) is a major disease of soybean and is widely distributed in soybean fields throughout the North Central region. The increase in the incidence of BSR is thought to be a result of shorter rotations between soybean and corn, which encourages a build-up of the brown stem rot pathogen.

Brown stem rot is caused by the fungus Phialophora gregata. The fungus survives mainly on crop residue left on the soil surface. In the spring, spores are produced that infect soybean roots.

The pathogen eventually reaches and invades the vascular system of soybean plants, and impedes the movement of water and nutrients needed for growth. Internal browning of the stem (see photo) is diagnostic for brown stem rot.

Internal browning, seen on the stem on the left, is diagnostic for brown stem rot. Photo credit: Craig Grau, University of Wisconsin

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