DISEASE SYMPTOMS:
Silver dollar size circular spots that are straw color and looks sunken-finer textured turfgrasses; dead spots are larger and more diffuse in courser textured turf; light tan spots with reddish brown borders radiate form the edge of the leaf blade; spots may cover width of blade; hour-glass shaped lesions on leaves; individual leaf blades may show both damaged and healthy sections; delicate mycelium stretching from leaf to leaf may be present in early morning when dew is present; small bleached spots appear on turf
HOST GRASSES:
Major hosts: Annual bluegrass, Creeping bentgrass, Colonial bentgrass, Bermudagrass (hybrid especially), Kentucky bluegrass, Perennial ryegrass, Zoysiagrass
Others: Fine fescues, St. Augustinegrass, Centipedegrass, Bahiagrass Tall Fescue
DISEASE CYCLE:
The pathogen is a facultative saprophyte, overwinters as mycelia in previously infected plants and as stromata on foliar surfaces; survives in local soils and infected turf residues; major problem on golf course greens; foliar and stem attacking fungus; spreads in plant debris via mechanical means-water , shoes, mowers, equipment; In the presence of moisture on leaves and favorable conditions, fungus grows and infects leaves-apparently does not infect roots, although fungal toxins produced may affect root formation; disease most severe in late spring and early summer and again in early fall.
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
Excessive thatch; low soil fertility; inadequate soil moisture; compacted soils; heavy prolonged dews; uncontrolled infection from previous year; continual use of one fungicide will allow fungus to develop resistance; temperatures between 70 and 80 degrees-moist, warm days and cool nights (60 degrees) in the spring, summer and fall.
CULTURAL CONTROL:
Removal of thatch; adequate soil fertility (nitrogen especially) program; deep infrequent waterings; aerification program; removal of dew in the mornings with water, mowing, etc..; good soil drainage; free air movement; remove clippings that may carry infection; raise cutting height.
CHEMICAL CONTROL:
Fungicide applications are very effective against this disease; alternate systemic and contact fungicides-systemics will give longer residual.
| Specific Fungicide Recommendations | ||||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
|
| Chlorothalonil | Good to excellent | 7 to 14 days | Daconil, Manicure, Thalonil, Chlorostar, Echo | |
| Iprodione | Good to excellent | 14 to 28 days | Chipco 26019, Chipco GT, Fungicide X | |
| Myclobutanil | Good to excellent | 14 to 28 days | Eagle, Immunox | |
| PCNB | Fair to good | 21 to 28 days | Terraclor, Turfcide, Defend | |
| Fenarimol | Good to excellent | 14 to 21 days | Rubigan, Patchwork | |
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.