As snows depart each spring, lawns often show damage that occurred during the winter. In particular, vole (mice) and snow mold (fungus disease) damage can be very destructive to lawns. There are preventative measures that can be taken to keep damage to a minimum.
Voles will make runways under the snow in lawns as they feed on grass blades and roots and are protected from predators. Voles, or meadow mice, are about 4 to 6 inches long and brownish-gray in color. Damage is frequently mistaken as mole damage, but moles are not active during winter and actually tunnel below the soil surface. Vole damage appears as runways or winding trails of damaged grass.
Lawns usually fill-in as conditions warm in spring. Severe damage may require some overseeding, however. Help prevent damage from occurring by continuing to mow lawns until grass is completely dormant in fall. Mow lawns at a final height of about two inches. Also clean up any excessive vegetation near lawns, as this provides cover for voles.
Snow mold damage can also be very visible on many lawns as snows recede in spring. Both gray (Typhula blight) and pink snow mold (Fusarium patch) may occur in northern Illinois. During the wet, cold weather of early spring, snow mold may be highly visible as matted, crusty looking areas. As conditions dry out, snow mold will gradually disappear but infected areas may remain in the form of weak or even dead turf.
Snow mold severity may vary from year to year, but certain turf areas seem to be frequently affected. Conditions which may contribute to snow mold include excessive use of fast-release (water soluble) nitrogen fertilizer in early to mid fall, excessive thatch, excessive shade, poor drainage, and excessive debris (such as leaves or straw) on the turf. Areas receiving drifting snow or piles of deposited snow are also prone to snow mold.
There are ways to avoid snow mold from becoming a severe problem. Follow sound fertilization programs, using fertilizers containing slow-release or controlled-release nitrogen. Adequate levels of phosphorus (P) and potassium (K) should be available in the soil. Manage thatch via aerification, or removal from vertical mowing (dethatching). Surface drainage should be adequate. Improve air circulation by pruning or removing dense vegetation bordering problem lawn areas. Mow lawns until completely dormant in fall.