DISEASE SYMPTOMS:
Small circular patches less than a foot in diameter; above ground damage are result of root injury in the spring and in previous fall; roots and rhizomes turn black and dark brown hyphae can sometimes be seen growing on them; injury most likely in spring and fall; older patches often have a healthy green center surrounded by a ring of dead brown grass-“frog eyed” appearance; some plants survive and grow back after fungus stops feeding in the center of the patch; infected leaves appear reddish-purple; similar to summer patch but more active in cooler weather; because roots, crowns, and rhizomes are rotted, plant are easily removed from turf
HOST GRASSES:
Major hosts: Kentucky bluegrass
Others: Annual bluegrass, Fine fescues, Creeping bentgrass, Rough bluegrass, Colonial bentgrass
DISEASE CYCLE:
Root, crown and rhizome attacking fungus; soil borne pathogen; spread by mechanical means; fungus more active in cool wet weather of spring and fall; unlike summer patch, the disease appears to be more prevalent on drought stressed turf and on soil that is organic rather than mineral
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
Low to deficient nitrogen level; compacted soils; plant water stress; alkaline soils; cool wet weather conditions - 58 to 82 degrees; excess thatch
CULTURAL CONTROL:
Use of moderate to low nitrogen levels-slow release types; prevention of drought stress; aerification program; reduce pH to below 6.5; light daily irrigation, maybe applied midday, cools turf and allows infected plants with depleted root system survive late afternoon heat stress; overseeding with perennial ryegrass if needed; replanting more resistant turf variety
CHEMICAL CONTROL:
Early spring applications of fungicides reduces severity but may not completely control disease. Fungicides need to be drenched into the soil before they dry on foliage because this is a root disease. Some fungicides like fenarimol and propicaonazole at hight rates slow down plant growth-so while you may control fungus, recovery of turf is not evident.
| Specific Fungicide Recommendations | |||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
| Azoxystrobin | Fair to excellent | 14 to 21 days | Heritage |
| Fenarimol | Fair to excellent | 7 to 21 days | Rubigan, Patchwork |
| Myclobutanil | Fair to excellent | 14 to 28 days | Eagle, Immunox |
| Iprodione | Fair to good | 14 to 28 days | Chipco 26019, Chipco 26GT |
| Propiconazole | Fair to good | 14 to 28 days | Banner Maxx |
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..
Decker, H. F., Decker, J. M. 1988. Lawn Care-A Handbook for Professionals. Prentice Hall. Englewood Cliffs, New Jersey.