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Cercospora Leaf Blight (Cercospora kikuchii)
University of Arkansas
Cercospora leaf blight is a late season disease that is often mistaken for early senescence. Symptoms are first observed at the beginning of seed set. Extensive losses from the disease have been reported in some years. While this fungus also attacks pods and causes purple seed stain, there is no consistent relationship between the occurrence of leaf spot and purple seed stain.
Symptoms are first observed at the beginning of seed set. Small, reddish-purple, angular to irregular lesions occur on the upper leaves which become leathery and dark purplish-red with bronze highlights. This discoloration may extend to the upper stems, petioles, and pods. Heavily infected leaves rapidly turn yellow and fall, mimicing senescence. Lower leaves remain green.
Although some cultivars possess resistance, control is primarily achieved by application of foliar fungicides starting at early pod set.