Stemphylium Leaf Spot

By  Wade Parker

Stemphylium leaf spot is a common cotton disease that impacts our lighter coastal plain soils. Stemphylium is typically associated with a severe potash deficiency. Given the right conditions, light leaf spotting can progress to heavy premature defoliation several weeks prior to harvest. Late season drought conditions along with a heavy fruit load will trigger this leaf spot disease. 

Stemphylium can not be controlled with fungicides, only pre-plant potash applications will greatly reduce the level of leaf spotting as well as premature defoliation. Usually, post-plant foliar potash applications do little if anything to slow this disease.

Severe defoliation from Stemphylium leaf spot.

Source:uga.edu