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Brown stem rot (BSR)

© Iowa State University

Pathogen(s) causing disease:

Cadophora (Phialophora) regata


The most common symptom is the brown to reddish brown discoloration of the stem pith. When disease is severe, the discoloration is continuous throughout the stem from the base of the plant upwards, and the outside base of the stems has a “greasy” appearance. Foliar symptoms, when present, consist of wilting, chlorosis, and browning of the tissue between the veins. Best way to identify brown stem rot of soybean is to split the lower stem of affected plants to check for brown discoloration. Healthy plants will have white pith.


Brown stem rot is more prevalent in no-till ?elds compared with tilled ?elds. No-till ?elds contain higher levels of crop residue, which allows for increased fungus survival and therefore higher inoculum levels.


Growing varieties with resistance to BSR is the most effective management option. Soybean varieties with resistance to both soybean cyst nematode (SCN) and genotype A of the BSR fungus can provide adequate protection. Rotation to other crops such as corn, alfalfa or small grains is an effective means of decreasing population levels of the pathogen and therefore reducing BSR severity. Since tillage promotes decomposition of infested crop residue, it is an effective method for inoculum levels and thereby reducing the risk of BSR disease. In addition, no-till ?elds tend to have lower soil temperatures and higher soil moisture levels, which favor the development of BSR. Also, research at Iowa State University has demonstrated that the presence of soybean cyst nematode (SCN) increases BSR disease in numerous soybean varieties. Therefore, SCN management should play a crucial role in BSR disease management.


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