Soybean stem canker, Cercospora leaf spot and anthracnose
scouted Aug. 5, 2025
- Background
- Soybeans in Camden county were scouted by grower and it was observed that the lower half of the pods seems to be necrotic and like the pods are dying off. About 70 % of the field is affected, this field is a sunny site and soybeans planted 3 weeks later in the same field are not showing symptoms as of yet. A sample was submitted to the PDIC for diagnosis.
- Conclusion
- Three issues were identified affecting this field, Soybean stem canker, Cercospora blight of soybean and anthracnose. Soybean stem canker is caused by 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 field. Lesions start out 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. Cercospora blight of soybean is caused by the pathogen Cercospora kikuchii and although it's common in soybeans it rarely causes significant yield losses in North Carolina. Chemical management and cultural practices are both options to control it. Anthracnose is caused by Colletotrichum. While usually a disease that shows in the stem, and the petioles it can also cause leaf curling and reddening of the veins. . Warm, wet weather favors infection and disease development. Crop rotation and tillage can reduce inoculum while foliar fungicides will reduce disease but it's usually not profitable.
