Infected leaves seem to be stiff, upright, and stunted in growth; appear as long yellow green streaks along the leaves; as disease progresses, the streaks become dull gray in color; cuticle and epidermis covering the streaks soon rupture and expose the blackish brown spore masses; leaf subsequently splits and curls from the tips downward, turns brown, and withers; in summer, infected plants often lack stress tolerance and die in irregular patches; black streaks on leaves
HOST GRASSES:
Major hosts: Kentucky bluegrass, Creeping bentgrass
Others: Colonial bentgrass, Annual bluegrass, Tall fescue
DISEASE CYCLE:
Attacks the meristamatic buds on crowns, rhizomes, and stolons; behaves as a systemic, perennial pathogen; Fungus overwinters as dormant mycelia in infected plant parts or as spores in the soil or on seeds; primary site of infection is through young seedlings or tillers; symptoms are not very obvious until spores rupture the epidermis of mature leaves; spores disseminated by wind, rain, mowing, irrigation, and other cultural practices; after infecting host, mycelia grow systemically throughout the plant.
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
Dry moderate cool temperatures of 50 to 60 degrees; high nitrogen fertility; excessive thatch; typically occurs in late spring or early fall; diseased plants very susceptible to high temperatures or dry conditions and often die in hot summer months; frequent irrigation
CULTURAL CONTROL:
Reduce nitrogen in summer but sustain moderate shoot growth; control excessive thatch; positive water balance-infrequent deep waterings; use seed treated with fungicides; use resistant cultivars
CHEMICAL CONTROL:
Properly timed fungicides will also help suppress smut development; systemic fungicides are effective in limiting new infections and systemic spread of pathogen; however, fungicides will not eradicate the fungus in plants already systemically infected; apply early spring, late summer and early fall when vigorous growth occurs-especially if there is a history of disease there.
| Specific Fungicide Recommendations | |||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
| Fenarimol | Fair to excellent | Fall, spring | Rubigan, Patchwork |
| Myclobutanil | Fair to excellent | Fall, spring | Eagle, Immunox |
| Propiconazole | Fair to excellent | Fall, spring | Banner Maxx |
| Thiophanate-methyl | Fair to excellent | 7 to 21 days | Cleary’s 3336, Cavalier, Fungo |
| Triadimefon | Fair to excellent | Spring | Bayleton, Accost, Granular Turf |
REFERENCES:
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.
Decker, H. F., Decker, J. M. 1988. Lawn Care-A Handbook for Professionals. Prentice Hall. Englewood Cliffs, New Jersey.