Caused by: Cercospora gossypina, Mycosphaerella gossypina
Foliar Symptoms: Reddish lesions will occur during the early stages. As the disease progresses, the lesions enlarge and turn white to light brown in the center. The lesions are circular and vary in size. Concentric zones are often present with a red color at the margins.
Diagnostic Note: In the field it is often difficult to differentiate Cercospora Leaf Spot from other foliar diseases. The spots appear concentric, like those of Target Spot, and the general distribution of spots on the plant may be the same as Stemphylium Leaf Spot and Alternaria Leaf Spot. Correct diagnosis often requires viewing the long, thin whip-like, septate spores. Caution should be taken as C. cassiicola spores can appear similar to Target Spot, but typically are broader and may have a basal scar.
Range and Yield Loss: Cercospora Leaf Spot occurs in all cotton producing areas within the U.S. When Cercospora Leaf Spot occurs while plants are under stress, or in a disease complex with Alternaria or Stemphylim Leaf Spot, premature defoliation, reduced yield, and lower fiber quality have been documented.
Maintaining plant vigor by having proper fertility and preventing drought stress through irrigation helps delay primary infections and reduce the severity of disease outbreaks.