• By Lindsey Thiessen •
Cercospora leaf spot of cotton (Fig. 1), caused Cercospora gossypina (syn. Mycosphaerella gossypina), has been observed across North Carolina cotton growing regions. Foliar symptoms include reddish lesions that enlarge to have white to light brown centers.
These symptoms may also be similar to other foliar diseases, like Stemphylium leaf spot or Alternaria leaf spot. Symptoms may also appear similar to target spot due to the presence of concentric rings.
For accurate identification, contact your Cooperative Extension agent and/or submit a sample to the Plant Disease and Insect Clinic.
This disease is usually associated with nutrient-deficient or stressed cotton. While it seems counter-intuitive to our experiences with other leaf spots that are more severe with wet conditions, this disease is often found associated with drought-stressed plants.
Plants that are unable to take-up potassium due to insufficient soil moisture or poor-root development are most prone to injury.
Significant losses may be observed from premature defoliation or when multiple foliar diseases are found. Fungicides alone are not an effective control for this disease.
Maintaining plant vigor with adequate soil fertility and preventing drought stress through irrigation where possible helps delay the onset and severity of outbreaks.
For more information regarding cotton disease management, see the 2019 Cotton Information book.
Dr. Lindsey Thiessen is an assistant professor and Extension specialist, Entomology & Plant Pathology, North Carolina State University. She may be reached at firstname.lastname@example.org.