Circular patches up to 2 ft. in diameter, with whitish-gray leaves matted together; light gray mycelia may be visible; brownish of black sclerotia may be imbedded in leaves and crowns; grass blades usually dead-but crowns and roots usually survive
HOST GRASSES:
Annual bluegrass, Creeping bentgrass, Colonial bentgrass, Perennial ryegrass
Others: Kentucky bluegrass, Tall fescue, Fine fescue
DISEASE CYCLE:
Fungus that inhabits most soils; pathogen becomes active in cold temperatures-only under snow cover ; special structures are produced by the fungus to ensure its survival during summer months; first noticeable in early spring-after snow melt is complete; commonly occurs in areas where snow accumulation is greatest; fungus survives summer as sclerotia, and it is ready to germinate and produce mycelia in late fall or winter under the reduced light of a snow cover and unfrozen ground; it coexists with pink snow mold and is separated visually by the presence of dark sclerotia from gray snow mold; pathogen a facultative saprophyte; under snow cover and temps just above freezing, mycelia overgrow the grass and produce infections; disease is quickly checked by increasing temperatures and sunlight, and decreasing moisture
FACTORS THAT MAY PROMOTE DISEASE DEVELOPMENT:
Occurs in cool temperate and subarctic climates; normally develops under a deep and prolonged (over 90 consecutive days) snow cover at temperatures of 30 to 45 degrees; poor soil drainage; high nitrogen fertility; excessive thatch; spread via wind and rain
CULTURAL CONTROL:
Use low to moderate autumn nitrogen to avoid excessive shoot growth; ensure rapid soil drainage; control thatch; mow to normal height in winter; rake grass in early spring to break up matting and promote drying; eliminating snow accumulations; don’t allow turf to get too high prior to and during winter-gets matted down and harder to dry
CHEMICAL CONTROL:
Some fungicide use may be required to control gray snow mold; not always practical or necessary.
| Specific Fungicide Recommendations | |||
|
Fungicide (chemical name) |
Efficacy |
Application Interval |
Example of Products (trade names) |
| Azoxystrobin | Good to excellent | 14 to 28 days | Heritage |
| Fenarimol | Good to excellent | 10 to 21 days | Rubigan, Patchwork |
| Iprodione | Good to excellent | 14 to 28 days | Chipco 26019, Chipco 26GT |
| PCNB | Good to excellent | 21 to 28 days | Terraclor, Turfcide, Defend |
| Propiconazole | Good to excellent | 14 to 28 days | Banner Maxx |
| Triadimefon | Good to excellent | 14 to 30 days | Bayleton, Accost |
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.