Snow Mold And What To Do About It In Winter

Some preventive work may help prevent its formation. When that first heavy blanket of snow falls onto your unfrozen lawn and stays, the conditions for snow mold are perfect. Mold loves the high humidity and temperatures just above freezing. The mold has been sitting there on your lawn just waiting for the opportunity to prosper, and it jumps at the chance as soon as the snow melts.

Snow mold appears as a patch of dull yellow to grayish-white grass, sometimes with a pink cast. Spots vary in size, but if you look closely, you’ll see the weblike mold weaving its way through the strands of grass. Pink mold is technically Microdochium nivale and more circular. Gray mold is usually Typhula incarnata and appears patchy.

For the most part, a healthy lawn will clear this up on its own, but you can do a few things when it thaws to help:

 Rake the grass and mats in the circles, removing what comes out, so the area dries out faster.
 If the grass is long, cut it again to help dry it out and let the sun get to it.
 Sow seeds if you don’t see new grass appearing in the area this spring.

In areas where snow mold is common, autumn preventive measures are wise. Make that last mowing about an inch or so lower than usual, but don’t go overboard. Suppose you’re already cutting your grass very short, good enough. Remove piles of leaves or thick grass clippings from the lawn. Use a fall fertilizer containing potassium and nitrogen, but don’t go overboard on the nitrogen. Mold loves nitrogen. You just want to give the grass the nutrients it needs to defend itself. After the last mowing and before it snows, look for a lawn fungicide like thiophanate-methyl and apply that per instructions.

The University of Massachusetts Cooperative Extension says these fungicides are effective against snow mold:

 Aromatic Hydrocarbon (contact): chloroneb
 Benzimidazole (penetrant): thiophanate-methyl
 Carboximide (penetrant): flutolanil
 Demethylation Inhibitor, DMI (penetrant): fenarimol, metconazole, myclobutanil, propiconazole,
tebuconazole, triadimefon, triticonazole
 Dicarboximide (penetrant): iprodione
 Nitrile (contact): chlorothalonil
 Phenylpyrrole (contact): fludioxonil
 Strobilurin (penetrant): azoxystrobin, fluoxastrobin, pyraclostrobin, trifloxystrobin

Premium, on-demand lawn-care services can factor these preventive measures into their annual fee, so proper lawn fertilization and fungicide are applied when needed. Leaves are removed to help ensure thick, green grass for the summer.