Circular patches up to 2 ft. diameter; light-brown to straw colored; may form a ring as result of turf recovery in center or invasion of off-type species; patches grow after few years; yellowing of leaves with often die; turf becomes thin as roots, nodes and stolons become infected and die; roots become rotted so damaged stolons easily pulled from the ground, similar to white grub damage; regrowth very slow; during summer months, weakened infected turf will continue to decline
HOST GRASSES:
Major hosts: Bentgrasses, Bermudagrasses, St. Augustinegrass
Others: Zoysiagrass, Centipedegrass, bluegrasses, Fine fescues, Perennial ryegrass
DISEASE CYCLE:
Pathogen overwinters as dormant mycelia in living and dead plant tissues; fungus forms dark brown to black ectotrophic runner hyphae on roots and stems of host plants; infection results where fungus penetrates subterranean plant tissues and spreads to adjacent plants by growing along roots and lateral shoots; most active in cool wet periods, but symptoms become more noticeable during drier conditions in early to midsummer; root and crown attacking fungus; soil and seed borne; most severe in 3rd and 5th years after planting and then declines; infection thought to occur more in fall and progressing in winter months
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
Poor drainage; low nitrogen; excessive irrigation; excessive thatch; soil compaction; alkaline soils above 6.3; moist cool conditions of 50 to 76 degrees; stressed turfgrasses
CULTURAL CONTROL:
Reduce soil pH to 5.5 to 6.0; avoid use of alkaline soil amendments; improve soil drainage; maintain water balance; aerification program; use of acidifying fertilizers; balanced fertility program; raise mowing height; do all you can do to prevent stress on turfgrass
CHEMICAL CONTROL:
Fungicides may or may not be effective; difficult disease to control; use a preventative program in fall and spring; fall applications probably more effective; very important to water fungicides in as deep as you can; replacing the turfgrass without applying a fungicide will only result in the infection of this disease to the new sod.
| Specific Fungicide Recommendations | |||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
| Fenarimol | Fair to Good | 30 days | Rubigan, Patchwork |
| Myclobutanil | Fair to Good | 28 days | Eagle, Immunox |
| Azoxystrobin | Fair | 28 days | Heritage |
| Propiconazole | Fair | Fall, spring | Banner Maxx |
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.