Soybean stem canker
scouted Aug. 25, 2025
- Scientific Name
- Diaporthe sp.
- Background
- Soybeans in Franklin County were being scouted, and it was observed that 40% of the field is affected by damping off, dieback, wilting, and blackening/browning after yellowing. Stems also appear hollow after plants turn from green to yellow. A sample was submitted to the PDIC for diagnosis.
- Conclusion
- The cause was identified as soybean stem canker, caused by the fungus of the genus Diaporthe. The first symptoms are often dead plants with dried leaves that remain attached to the petioles late in the season. The diseased plants usually occur in patches within the field. Lesions start as small reddish-brown spots at the base of a branch and then expand to form sunken cankers. In some cases, it can cause top dieback by forming a dark brown canker on the upper internodes, which kills only the top of the plant. Unfortunately, there are limited management practices to implement, as it is best managed with resistant varieties and crop rotation to non-host crops such as corn or wheat, as the pathogen survives in soybean residue. There is no data currently on fungicide efficacy for management.
- Resources
