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Publication #SS-PLP-57

Cercospora Leaf Spot1

M. L. Elliott and P. F. Harmon2

Cercospora Leaf Spot

Pathogen: Cercospora fusimaculans

Turfgrasses Affected: St. Augustinegrass

Occurrence: This disease is observed between the late spring and summer seasons, especially during periods of frequent rainfall. Areas of St. Augustinegrass that are under cultural or environmental stresses are more susceptible to disease development. Areas of turf under low fertility or suboptimal light conditions seem to develop this disease.

Symptoms/Signs: Initial symptoms are narrow, dark brown leaf spots that enlarge over time into oblong to irregularly shaped lesions with dark tan centers and dark brown to purple margins (Figure 1). Under humid conditions, the abundant sporulation of the pathogen in the lesion centers may confer a whitish sheen to the spots. Numerous spots on multiple leaves can cause extensive yellowing and withering of the canopy.

Figure 1. 

Cercospora leaf spot symptoms on St. Augustinegrass.


Credit: G. W. Simone
[Click thumbnail to enlarge.]

This disease is very similar in pattern on the lawn and symptoms to that of gray leaf spot, but management is very different.

Cultural Controls: Prevent the disease by fertilizing adequately, using slow-release nitrogen sources balanced with potassium (preferably, a slow-release potassium form). Examine the irrigation cycle for timing, frequency, and amount. Time irrigation so as not to extend the dew period (between 2:00 and 8:00 a.m.). Water only when the turf exhibits moisture stress. Avoid daily, frequent irrigation cycles that promote foliar disease. 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 (N:K ratio of 1:1). Apply 1/2 lb N per 1000 sq ft, using an ammonium nitrate, ammonium sulfate, or quick-release urea formulation. Where Cercospora leaf spot is persistent, St. Augustinegrass cultivars derived from 'Bitterblue' types offer more resistance to this disease.

Chemical Controls: None available.

Refer to the "Turfgrass Disease Management" section of the Florida Lawn Handbook (http://edis.ifas.ufl.edu/lh040) for explanations of cultural and chemical controls.

Footnotes

1.

This document is SS-PLP-57, one of a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date April 2001. Revised February 2011. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

M. L. Elliott, professor, Plant Pathology, Fort Lauderdale Research and Education Center; and P. F. Harmon, associate professor, Plant Pathology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.