Brown spot of tobacco
scouted Oct. 2, 2026
- Scientific Name
- Alternaria alternata
- Background
- A tobacco field in Lee County was being scouted, and it was observed that 15% of the field was affected by spots in patches throughout the field, with some galling on plant roots, suspected to be a nematode issue. Brown spot and target spot were observed in the field, with the grower finding some angular spot as well. A sample was submitted to the PDIC for diagnosis.
- Conclusion
- The issue was identified as brown spot of tobacco. This foliar disease is caused by Alternaria alternata or Alternaria longipes and survives in soil and crop debris. Moisture is required for spore germination and infection of host tissue, and disease development is favored by warm, wet conditions. Symptoms include small circular to irregular lesions that begin small and expand as the disease progresses. Lesions are dark brown and often surrounded by yellow halos. Brown spot may continue to develop during curing, resulting in moldy growth on cured leaves known as barn rot. Management of brown spot relies on cultural practices that reduce fungal inoculum and delay disease development, as there are no effective registered chemical controls for this disease in tobacco.
- Resources