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Battling Gray Snow Mold in Cold-weather Lawns

by Sue Booth, All About Lawns Columnist

Lawns in snowy climates can fall prey to Typhula blight, more commonly known as gray snow mold. Affected lawns can look healthy at the end of the growing season as the lawn goes dormant. Then, under the top-pack of winter snow, the fungi that cause the blight begin growing in the grass thatch. Once the snow begins to melt in the spring, the tell-tale, matted spherical patches of mold appear on the lawn.

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Typhula blight can begin as small in circumference as a pinhead, but can swell to discs of dead grass as wide as two feet across. The best way to fight this particular blight is to prevent it from occurring in the first place. If you live in a climate with heavy snowfall, avoid heavy nitrogen fertilizing each fall and mow your lawn a little lower as winter comes. Keep your thatch under control and spread new fallen snow across the lawn, avoiding large drifts that can foster mold growth below the surface.

Treating Blight with Fungicides

According to experts at the University of Massachusetts Extension Turf Program, PCNB is one of the more effective fungicides in treating Typhula blight. Other combinations, including fludioxonil and propiconazole or iprodione and chlorothalonil, can help stem off the mold. Fungicides vary in effect according to climate, so it pays to consult a local lawn care expert before treating blight in your region.

Another preventative measure, U Mass researchers found, is in slowly cutting back on your watering regimen in the fall. The heartier the lawn, the less vulnerable it is to the fungus. Once your lawn dries out in the spring, the fungus typically abates. But by then, you may have to reseed large sections of grass that were killed by the spring blight.


University of Massachusetts Extension Turf Program

About the Author
Sue Booth is a consumer products freelance writer and a former product analyst for Good Housekeeping magazine. Sue holds a B.S. in Mechanical Engineering.

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