In general, leaf spots are first visible on older leaves at the bottom of the plant then spread upward toward the top of the plant. Initial spots are purple and small with a circular shape. As spots enlarge, they often become irregular or angular in shape and develop a tan or gray center surrounded by a purple or brown border. Leaves that are severely spotted often become a yellow-green color.
Initial infection usually occurs during May, but symptoms don’t become apparent until later in the season. Midsummer environmen tal conditions contribute to disease severity. Rainfall and overhead irri gation are major factors that play a pivotal role in symptom expres sion and intensity. Late summer rainfall can be a major contributor to defoliation and decline.
