How to get rid of Grey Snow Mold
Winter is melting away, the sun is shining, the air is warming up and it feels like spring has finally sprung in your garden. You watch in eager anticipation as the snow retreats from your lawn, impatient to get out there and revel in the new season. But what’s this? Ugly circles of dead-looking brown patches and matted grass? Congratulations you have Grey Snow Mold. It usually occurs when heavy snow cover sticks around until the start of spring before thawing and you’ll probably find it in areas where the snow has been particularly dense or has accumulated in drifts. Don’t panic – it’s totally treatable and you can also prevent it returning next year.
How did it get into my lawn?
Your lawn was infected last fall when the microdochium nivale fungus started to incubate in the grass. During the warm weather the fungus produced sclerotia which, as winter arrived, in turn produced the spores that created the infection. It used the cover of a deep and lasting snowfall to cheerfully grow and spread, undetected by you.
How do I recognize it?
The first thing you’ll notice as the snows recede will be circular or irregular patches of yellowish grass that turns brown as the weather warms up. Grey Snow Mold only kills the blades of the grass, not the roots or crown so your lawn isn’t dead. But if left untreated, any individual patches will grow, spread and merge together. If the lawn stays wet due to a prolonged damp spring, a white or pinkish cotton-like pinhead fungus will also appear at the edges of the patches.
How do I get rid of it?
You could just leave it alone – the grass isn’t dead after all – and new grass will eventually push through. But the problem will come back with a vengeance next year and the patches will get bigger, uglier and harder to ignore.
Once the lawn is completely dried out all you need to do is rake up the infected grass to allow air to circulate in the exposed soil, promoting new lawn growth. If you also regularly mow and fertilise your lawn, this will help stop future growth of the fungus. But while you should continue mowing well into the Fall, even when the grass is dormant, ease off on fertilisation during these months so that any returning fungus has nothing to feed on.
The chemical treatment of domestic lawns for Grey Snow Mold is not recommended so you should only try this of all else has failed. Look for fungicides with the active ingredients azoxystrobin or
propiconzole. Or use iron sulphate (a generic moss killer) which also toughens the grass and deters future mold infection.
To make sure you’re not faced with the same problem next year, keep your lawn well moved through the warmer months, removing any loose clippings and dead leaves, and avoid leaving deep snowbanks on grass when clearing snowfall.