Mold Patch on Lawn Grass

Slime and snow mold patches can occur on both warm and cool season grass varieties. Slime molds are primitive organisms, according to the Connecticut Agricultural Experiment Station's website. Snow molds are fungi that thrive under snow, according to Iowa State University.

Appearance

• Slime mold occurs under warm, moist weather conditions. The patches of mold usually occur in spots that measure 4 to 6 inches in diameter to several feet. The infected area appears to be covered in a white, gray, or black coating.

  The fungi that cause snow molds create irregular circles in the lawn in shades of pink, white, gray or black during late winter, according to the University of Rhode Island.

Effects

• Grass foliage will eventually begin to yellow in areas afflicted with mold. Mold covering the grass prevents both light and oxygen from reaching the leaves. Left to colonize on the grass blades, molds will eventually kill the lawn area affected.

Prevention/Solution

• Mow infected areas and lightly rake the thatch away in areas where slime or snow molds occur. Spraying the infected patch with a hard stream of water will also tear away the mold from the grass blades.

  For prevention, plant grass in areas that are well-drained. Remove thatch build up promptly. Use a preventative fungicide in the fall to keep snow molds from occurring.