|  |
Cercospora Leaf Spot1
M. L. Elliott and G. W. Simone2Cercospora Leaf Spot
- Pathogen: Cercospora fusimaculans
- Turfgrasses Affected: St. Augustinegrass
- Occurrence: This disease is observed between late spring and the 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 sub-optimal 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 ( Plate 9 ). Under humid conditions, the abundant sporulation of the pathogen in the lesion centers may confer a whitish sheen to the spots.
CREDITS: G. W. Simone
Plate 9. Cercospora Leaf Spot symptoms on St. Augustinegrass.
- Numerous spots on multiple leaves can cause extensive yellowing and withering of the canopy. 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 and 8 AM). 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 ½ pound N per 1000 square feet utilizing an ammonium nitrate, ammonium sulfate or quick release urea formulation.
- Where this disease is persistent, choice of St. Augustinegrass cultivars derived from bitter blue types offer more resistance to this disease.
- Chemical Controls: chlorothalonil, mancozeb, myclobutanil, thiophanate methyl, or triadimefon.
- Mancozeb can be applied to a residential lawn only by a professional pesticide applicator. Chlorothalonil cannot be applied to a residential lawn, but it can be applied to turfgrass in a business or industrial landscape.
- Refer to "Turfgrass Disease Management" section of the Florida Lawn Handbook for explanations of cultural and chemical controls.
Footnotes
1. This document is SS-PLP-57, a series of the Plant Pathology Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. This information is included in the Florida Lawn Handbook, SP-45. For a copy of this handbook, request information on its purchase at your county extension office. First published: April 2001.2. M. L. Elliott, Associate Professor, Plant Pathology, Fort Lauderdale Research and Education Center, and G. W. Simone, Emeritus 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 extension publications, contact your county Cooperative Extension service.
U.S. Department of Agriculture, Cooperative Extension Service, University of Florida, IFAS, Florida A. & M. University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Larry Arrington, Dean.
Copyright Information
This document is copyrighted by the University of Florida, Institute of Food and Agricultural Sciences (UF/IFAS) for the people of the State of Florida. UF/IFAS retains all rights under all conventions, but permits free reproduction by all agents and offices of the Cooperative Extension Service and the people of the State of Florida. Permission is granted to others to use these materials in part or in full for educational purposes, provided that full credit is given to the UF/IFAS, citing the publication, its source, and date of publication.