Cercospora Leaf Spot

Identification

Initial symptoms are narrow, dark brown leaf spots. Over time, these spots enlarge into oblong to irregularly shaped lesions with dark tan centers and dark brown to purple margins.
This disease is very similar in pattern on the lawn and symptoms to that of gray leaf spot.

Environment

This disease is observed between the late spring and summer seasons, especially during periods of frequent rainfall. Areas of St. Augustine Grass that are under cultural or environmental stresses are more susceptible to disease development. For example, low soil fertility or sub-optimal light conditions are conductive to the development of this disease.

Threats

St. Augustine Grass.

Treatment

The disease can be prevented by fertilizing adequately, using slow-release nitrogen sources balanced with potassium. Irrigation should only occur in the early morning hours (between 2:00 and 8:00 a.m.) when dew is already present. Daily, frequent irrigation cycles can promote foliar disease and should be avoided. If Cercospora leaf spot is already present, the disease can be managed with the application of quick-release nitrogen in a fertilizer blend balanced with potassium.