Snow mold can be a problem during cold, wet autumn and spring weather and under the snow in winter. As snow melts, patches of grey, white or pink fuzzy mold appear on the grass. The grass blades may turn yellow or brown. Circular to irregular patches of turf may die and occasionally form large areas of dead grass.
Turf is most at risk when snow falls on unfrozen, wet ground. Heavy snow accumulation that lasts late into spring allows the disease more time to develop. Excessive nitrogen fertilizer forces the turf to grow late into autumn and so the turf does not "harden-off" for winter and is more susceptible to these fungi.
To manage snow mold, use slow-release nitrogen fertilizers earlier in the season, reduce fertilizer application and irrigation in late summer to allow the turf to harden off. For the last mowing of the season, adjust mower cutting height to about two inches, so grass does not mat' under snow. Rake up fallen leaves and other moisture-holding debris. In the spring, break up piles of snow, if feasible, to speed melting. Pick up grass clippings and manage thatch, keeping thatch layers less than 3/4" thick. If soils are compacted, aeration and improving drainage may help. When the lawn has dried in spring, use a stiff broom to break up the patches of mold.
In home lawns, chemical control is rarely required. If chemicals are used, apply flowable sulfur fungicide or other labeled fungicide to the infected areas every three to five days until the symptoms disappear.
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