Soybean stem canker
scouted Sept. 26, 2024
- Scientific Name
- Diaporthe sp.
- Background
- Soybeans in Cumberland County were scouted, and it was observed that about 30% of the field was affected by randomized browning. The previous year (2023), the field was planted with tobacco and treated with Command 3E as well as Spartan herbicides. In 2024, soybeans were planted after a burndown of the ryegrass cover crop in May. Velum was applied at planting (4 oz/acre), along with Gromolone and Envive herbicides. Follow-up herbicides included Roundup and Liberty. The first insecticide application consisted of bifenthrin and boron, while the second insect spray was Beleaf. The soybean seed was untreated. Issues were present during early season but began to look better. After Tropical Storm Debbie, issues progressed and continued to worsen following heavy rainfall in late September. The field is very sandy, yet still held a large quantity of water. Samples submitted include plants from multiple locations, including both healthy and affected areas.
- 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 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.
- Resources
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- No resources have been added.
