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What causes Snow Mold disease in lawns?

Submitted by Anonymous (not verified) on Fri, 2013-02-08 08:24

It’s the dead of winter on the cusp of a blizzard of historic proportions so what better lawn care topic to discuss than that of Snow Mold?

Pink snow moldSnow Mold is a disease of the foliage of turfgrass that occurs during cooler temperatures, not necessarily when there is snow. It will show up in patches of either pink or gray matted turf that under the right conditions will expand until they begin to coalesce into a much larger mass of diseased turf. To say that it can be visually dramatic is an understatement.

However, under most circumstances, it will not permanently damage the lawn. An explanation is in order to describe why that is.

Fungi play an enormous role in keeping nature from overrunning us with her refuse. Did you ever consider where all the leaves on the trees go once they’ve fallen in autumn? Sure, you raked up the leaves that fell on your lawn but that is an insignificant amount compared to the whole. If there were no mechanism, no process of breaking down those leaves they would soon pile up so high that they would be taller than the trees themselves.

Enter the fungi. Although turfgrass managers spend considerable time and effort protecting the grass they grow from infections caused by fungi, only a small percentage of the species of fungi cause disease in plants.

Disease causing fungi are referred to as pathogenic, (pronounced "path-oh-jen-ic") the prefix ‘patho’ comes from ancient Greek meaning ‘disease’, while the suffix ‘genic’ means ‘producing or causing’. Putting those together, ‘pathogenic’ means producing or causing disease. (Easy, right?)

Most fungi are not pathogenic, but rather saprophytic (pronounced "sap-row-fit-ic"). ‘Sapro’ indicates dead or dying matter, while ‘phytic’ comes from the Greek word ‘phyton’ meaning plant. Putting those together, we get a fungus that feeds upon dead and dying plant material.

Snow mold upcloseMost of the time, the Snow Molds are saprophytic, feeding upon the dead leaf tissue left over from last season. What you may not realize is that when the lawn comes out of dormancy in the spring, the leaf tissue that you see on the lawn right now does not come back to life – its dead as a door nail.

Rather, the grass plant will send up brand new leaves from its crown, the central growing point that is located at the soil surface. The dead leaves you see on the lawn right have to go somewhere, and that somewhere is back into the soil as organic matter to be recycled over and over again. Fungi like the species that cause the Snow Molds have an important role in the health of our lawns.

There are instances where the Snow Molds will attack the crowns, the growing points, of the turfgrass plants, and that’s where they can cause a lot of problems. Most of the time though that is on sports turfs that are cut closely, such as golf courses and soccer pitches. On home lawns, however, a gentle raking in the spring to break up the matted leaves is usually enough to get the ball rolling again.

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