DISEASE SYMPTOMS:
Formerly cottony blight, damping off, or greasy spot; one to six inch diameter patches of irregular shape or even streaks; leaves initially water soaked to greasy, then turn tan; white to gray, cottony mycelial growth may be evident in early morning on green leaves; patches sometimes develop into diffused streaks that follow water drainage patterns or mowing patterns; pythium kills grass right down to the crowns; the centers of the patches are matted down usually with a brown or tan color; leaf lesions white and hour-glassed shaped but lacking reddish-brown margins; infected turf appears flat or matted
HOST GRASSES:
Major hosts: Annual bluegrass, Creeping bentgrass, Colonial bentgrass, Tall fescue, Perennial ryegrass
Others: Kentucky bluegrass, Fine fescue, Bermudagrass (especially hybrids), Zoysiagrass
DISEASE CYCLE:
Very destructive pathogen that destroy turf in a matter of hours under right conditions; particularly destructive to new seedlings; fungi survive winter as soil saprophytes or as dormant mycelia in plants infected the previous winter; most active with temperatures of 85 to 95 degrees, high humidity, and warm nights; has been reported with temps of 60 degrees when overwatering for rapid germination of seedings has resulted in high humidity; cause more root rot and injury to crown of plants-infection results in slower growth, poor color and general thinning of turfgrass; one of major causes of a poor transition from overseeded grasses to bermudagrass in late spring; under right conditions, mycelium resumes growth and spores germinate; disease development occurs rapidly from center of origin by a cob-web like mycelial growth from leaf to leaf; rapid spread occurs when strands or spores are moved by water or equipment across the turf; spores may survive indefinitely in soil or by themselves or associated with infested residue.
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
Poor drainage; excessive nitrogen-lush green growth; poor air movement; high pH soils; weather conditions of temperatures 85 to 95 degrees-humid, warm nights; excess thatch; overwatering
CULTURAL CONTROL:
Improve soil drainage; aerification program; moderate use of nitrogen; maintain soil pH in acid range below 6.5; minimize periods of leaf wetness; avoid excess irrigation; improve air movement; use treated seed; water deeply in morning; do not mow wet grass in hot weather
CHEMICAL CONTROL:
During extended periods of warm humid weather, a preventative fungicide program may be needed; applications need to be made where there is a history of the disease or when conditions are favorable; fungicide treatment may be needed 7 to 21 days after planting to protect seedlings; effective systemic fungicides may be needed
| Specific Fungicide Recommendations | |||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
| Azoxystrobin | Good to excellent | 10 to 14 days | Heritage |
| Ethazole | Good to excellent | 5 to 10 days | Koban, Terrazole |
| Fosetyl-Al | Good to excellent | 14 to 21 days | Signature, Aliette |
| Metalaxyl | Fair to excellent | 10 to 21 days | Subdue |
| Propamocarb | Fair to excellent | 7 to 21 days | Banol |
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.