Circular patches .5 to 3 ft. diameter; initially yellowish; gradually turning brown and thinning; roots darkened; chlorotic leaf blades may develop next to green shoots at margins of diseased area; roots brown and without feeder roots and root hairs; root surface appears as dark brown hypal runners; runner hyphae may be visible during microscopic examination.
HOST GRASSES:
Major hosts: Bermudagrass, St. Augustinegrass
Other hosts: Zoysiagrass, Centipedegrass
DISEASE CYCLE:
Symptoms most evident in late summer (hot, wet periods) and early fall-fungus organism most active during fall, winter and spring in moderate temperatures and abundant moisture; root attacking fungus; spread by mechanical means and plant-to-plant contact; fungus grows on the surface of roots, stolons, rhizomes, crown and leaf sheaths-and then penetrates and infects the tissues; pathogen survives on infected debris and infected perennial parts of living grass plants
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
Cool, moist weather are conditions which favor growth of the fungus; symptoms increase in summer months; stressed turfgrasses-low mowing heights, water stress, excessive thatch, excessive fertilization, compaction, alkaline soils, etc.. promote the disease.
CULTURAL CONTROL:
Raise cutting height; maintain moderate nitrogen; control excessive thatch; positive plant water balance, soil acidifiers in alkaline soils; use of ammonium sulfate to decrease pH; aerification program; some research has been done using higher rates of ammonium sulfate and moderate aerification on bermudagrass greens-Dr. Richard White.
CHEMICAL CONTROL:
Fungicide applications are not very effective; proper cultural practices, especially in the infected areas, are a must.
| Specific Fungicide Recommendations | |||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
| Fenarimol | Moderate | 30 days | Rubigan |
| Azoxystrobin | Fair | 28 days | Heritage |
| Propiconazole | Fair | 30 days | Banner Maxx |
| Myclobutanil | Fair | 28 days | Eagle |
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.