White to gray, dusty patches of fungal growth on leaves and stems and leaf sheaths; areas enlarge; chlorotic lesions may develop; entire leaf turns yellow and eventually dies; surviving plants weakened; when growth is dense-looks like lime spread over it
HOST GRASSES:
Major hosts: Kentucky bluegrass, Fine fescues
Others: Ryegrasses, Bentgrasses, Bermudagrasses, Zoysiagrasses; on annual grasses used for overseeding
DISEASE CYCLE:
Fungus present during most of growing season; most active in cool, humid, cloudy weather with temperatures of 60 to 70 degrees-spring and fall mostly; especially active in shady areas where air circulation is poor and humidity is high; prevalent on overfertilized bluegrass and fescue under these conditions; cycle is very rapid-spores that land on susceptible plant germinate quickly and spread in few days; overwinters as dormant mycelium or as spores contained in small black fruiting bodies in the turf debris; spores are disseminated by the wind and quickly infect new leaves, producing germ tubes that grow directly through the cuticle and epidermis into the interior of grass leaf; when germ tube comes in contact with cell in grass leaf, it produces a specialized absorptive structure (haustorium) and sets up a parasitic association, living off the grass leaf without killing it-can be quite damaging to grass plant; shoot attacking fungus
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
Shady areas; poor air circulation; temperatures 60 to 70 degrees; cool humid conditions; close mowing; high nitrogen fertility
CULTURAL CONTROL:
Reduce shaded area; improve air circulation; increase mowing height; use moderate nitrogen; use shade tolerant cultivars
CHEMICAL CONTROL:
Fungicides can be used successfully if disease persists.
| Specific Fungicide Recommendations | |||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
| Fenarimol | Good to excellent | --- | Rubigan, Patchwork |
| Myclobutanil | Good to excellent | 14 to 28 days | Eagle, Immunox |
| Propiconazole | Good to excellent | 14 to 30 days | Banner Maxx |
| Triadimefon | Good to excellent | 14 to 30 days | Accost, Bayleton, Proturf |
REFERENCES:
Duble, R. L. 2001. Turfgrassed-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.
Decker, H. F., Decker, J. M. 1988. Lawn Care-A Handbook for Professionals. Prentice Hall. Englewood Cliffs, New Jersey.