Yellowish chlorosis, then turns brown; numerous oblong, gray to ash-brown leaf lesions with purple margins; grayish spore producing bodies may be noticable on these lesions; leaves sometimes appear twisted; death of infected leaves; yellowing turf that appears drought stricken
HOST GRASSES:
Major hosts: St. Augustinegrass, Perennial ryegrass
Others: Bermudagrass, Fescues, Centipedegrass
DISEASE CYCLE:
Foliar attacking fungus; symptoms of general melting out occur on cool season grasses while symptoms on warm season turfgrasses involve lesions and blights of leaves; Pathogen overwinters as dormant mycelia and free spores in older infected leaves and debris-new infections occur during warm moist weather in spring and continue into the summer and fall months; phenomenal rate of spore production-“blast”; leaf spots enlarge and girdle and kill the grass;
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
High nitrogen fertilization; high humidity; 80 to 90 degree days and above 70 degree nights; shaded areas; herbicides that weaken turf; compacted soils; thatch problem; drainage problems
CULTURAL CONTROL:
Moderate to low nitrogen applications-especially in shady areas; adequate drainage and irrigation; do not water in late evening; control thatch and compacted soils; catch and remove clippings where problem exists
CHEMICAL CONTROL:
Intensive use of fungicides may be required if fungus appears.
| Specific Fungicide Recommendations | |||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
| Azoxystrobin | Excellent | 14 to 28 days | Heritage |
| Myclobutanil | Fair to good | 14 days | Eagle, Immunox |
| Propiconazole | Good | 14 days | Banner Maxx |
| Thiophanate-methyl | Good | 7 to 14 days | Cleary 3336, Fung Flo, Cavalier |
REFERENCES:
Duble, R. L. 2001. Turfgrasses-Their Management and Use in the Southern Zone. Second Edition. Texas A&M University. College Station, Texas.
Emmons, R. D. 2000. Turfgrass Science and Management. Third Edition. Delmar Thomson Learning. Albany, New York.
Turgeon, A. J. 2002. Turfgrass Management. Sixth Edition. Prentice Hall. Upper Saddle River, New Jersey.
Beard, J. B. 2002. Turfgrass Management for Golf Courses. Second Edition. Ann Harbor Press. Chelsea, Michigan.
Taylor, G. R. - Editor. 2000. Turfgrass Pesticide Recommendations 1999-2000. Extension Publication SCS-1991-01. Texas A&M University. College Station, Texas.