Cercospora Leaf Spot on Pansy By Dr. Steve Nameth Department of Plant Pathology, The Ohio State University Columbus, OH 43210 Cercospora leaf spot is a common disease of pansy. The disease is caused by a variety of species within the Cercospora genus. However, all of the species cause similar symptoms on the affected host. Leaf spots tend to be first noticed on the older leaves or leaves that are close to the soil or media surface. Initially leaf spots are 1-3 mm in size with a sunken center (Figure 1) and (Figure 2). The leaf spots appear to be purple in color with a web-like growth pattern (Figure 3). If left unchecked the leaf spots will continue to expand, coalesce, and may cover the whole leaf. These leaves may turn yellow and drop off the affected plant. If not controlled this leaf spots can cover the entire plant and cause premature death. The best way to control Cercospora Leaf Spot is to keep the leaves free of moisture for extended periods. Water early in the morning. This will allow the leaves to dry going into the coolness of the evening. There are a variety of fungicides that are labeled for this disease on pansy. These include Cleary's Protect T/O, Daconil, and Medallion. Products containing Mancozeb tend to be the most effective.