Wednesday, March 17, 2010

Snow mold in your lawn this spring

Snow mold is a fungal disease that appears in the early spring when temperatures are cool and the ground is wet - first visible when the winter snow melts. There are two types of snow mold - pink snow mold and gray snow mold.

Snow mold damage looks like circular patches (2"-12") of dead and matted grass - often mistaken for dead or dying patches of grass.  Depending on the severity of the outbreak, the circles can grow together and become a large mass. It is not uncommon to find both gray and pink snow mold together in the same lawn.

Pink snow mold (picture below) is distinguished by the pink color of the web-like mycelium growing on the grass surface (see picture below). While the grass is wet, the mycelium looks like cobwebs, as it matures it turns its pink or salmon color.  Pink snow mold infects the crown of the plant and can cause more severe injury than gray snow mold. 
Gray snow mold (picture below) is similar to pink snow mold except that its mycelium remains whitish-gray and only infects the blade of the turf grass plant. Gray snow mold is also distinguished by the presence of tiny black mycelial masses on the grass blades and leaf sheaths of infected plants which pink snow mold does not produce.

The cause of snow mold:
Snow mold can occur even when there is no snow, however, it is generally  more severe when snow increases the amount of moisture, reduces sunlight and prevents the lawn from drying out.  Thicker layers of leaves can have a similar impact as snow cover on the grass creating a more ideal environment for snow mold. 
Good cultural practices will help to reduce the appearance and impact of snow mold:  
  • Avoid excessive nitrogen fertilizers in the fall
  • Mow the lawn in the fall until it stops growing
  • Thorough fall clean up removing leaves and debris from the lawn
  • Manage thatch to avoid accumulations of more than 2"
Repairing snow mold damage: 
Fungicides are available for both curative and preventative treatments of snow mold. However, they are not recommended due to the temporary damage snow mold inflicts on the lawn.

Even though a lawn infected with snow mold can look horrible in early spring, most snow mold damage will recover as temperatures warm and the grass begins to grow out. Once the area has dried, the infection will cease and the turf will grow out and renew itself making snow mold damage practically disappear.

To speed the recovery process it is best to lightly rake the infected area to increase air flow to the grass and encourage drying. Some overseeding may be necessary if there is extreme damage and recovery is slower than desired.

Written by:
Eric Johns, Lawn Care Specialist
Adam Perkins Sr, Landscape Industry Certified

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