Descriptions

Pink Snow Mold

Symptoms on bentgrass turf begin as small, circular spots which develop into rusty-brown patches, six to eight inches in diameter. Under ideal weather conditions, the disease progresses so rapidly that the grass in the center of these circular patches begins to grow again, producing a ring-like effect. These spots are usually less than a foot in diameter, but may expand up to two to three feet in diameter. Grass at the outer edges of the ring is thinner and, when wet, a white to salmon-pink moldy growth is visible on infected grass blades.

On Kentucky bluegrass, Poa annua, fescues, and ryegrasses, symptoms are more or less circular spots, mostly in the 4- to 12-inch diameter range. Within these spots, the grass is bleached and matted. Some spots may be a uniform bleached color and others may have a bleached center with a rusty-brown or salmon-pink border. The scattered spots are easily detected, even in mid-winter, because of the contrast in color between the diseased spots and dormant turf.

Grey Snow Mold

Gray snow mold is strictly a cold-weather disease and is called gray snow mold because of the characteristic dirty-white to gray mycelium formed on infected turf.

Soon after the snow melts, the infected grass may be matted and surrounded by a white to gray halo of fluffy fungal growth.

The gray snow mold fungi spend the warmer months as sclerotia embedded in infected grass blades and in the turf canopy. Sclerotia are very small black to orange structures that can survive hot, dry conditions. Heavy moisture and near-freezing temperatures trigger germination of sclerotia and infection of grass plants.

A situation that often produces these key conditions is a deep snow or heavy mulch covering wet turfgrass before the ground has frozen. Early winter snows are often heavy and wet and may cover the turf for several weeks. This early snow cover initiates the disease. Gray snow mold activity will be slowed when the snow cover is gone due to winter thaws, but the activity will resume every time it snows, regardless of whether it is a light flurry or heavier snow. Injury to the turf is aggravated when the snow is compacted by walking, skiing, snowmobiling, or sledding. Succulent growth produced by early fall fertilization is a prime target for attack by snow mold fungi.

Gray snow mold develops where snow has drifted or been piled and is slow to melt. Patches of rough, dead, bleached-brown areas up to a foot in diameter become visible as melting snow recedes from infected areas. These patches appear scalded, with leaves being matted together. They are often, but not always, covered by a whitish-gray moldy growth. As the grass dries, the leaves become silvery white, brittle, and encrusted over the patch. Extensive areas of turf may be damaged when the patches overlap due to enlargement of existing patches and development of new ones.

From a distance, symptoms of pink snow mold on residential lawns are very similar to symptoms of gray snow mold.

When pink & gray snow mold occur in the same turf at the same time, visual symptoms of the two snow molds might be confused. The two diseases can be separated when samples of infected turf are stored in a plastic bag in a refrigerator for two weeks. The Gray Snow Mold fungi develop tiny orange to black sclerotia embedded in infected leaves, which are usually white and brittle, while those infected by Pink Snow Mold may be pink and tough.

Favorable Conditions

Pink Snow Mold

Prolonged, cool, wet weather. When temperature and moisture conditions favor infection, the fungus produces thousands of spores on previously infected plant tissue. These spores and diseased leaf fragments are spread by traffic through the affected area.

Grey Snow Mold

Heavy moisture and near-freezing temperatures trigger germination of sclerotia and infection of grass plants. A situation that often produces these key conditions is a deep snow or heavy mulch covering wet turfgrass before the ground has frozen.

Susceptible Grasses

Pink & gray snow mold are diseases that may affect all cool-season turfgrasses.

Pink snow mold appears to be most damaging to creeping bentgrass and annual bluegrass on golf courses. Juvenile creeping bentgrass (less than 1 year after seeding) is most susceptible and is likely to have the most lasting effects.

On kentucky bluegrass and perennial ryegrass in lawns and professional landscapes, pink & gray snow mold is most prevalent on turf maintained at a height of 3 inches or greater.

Management Recommendations
& Cultural Control Options

Cultural control options are the same for both diseases.

Rake Leaves and Avoid Snow Piles on the Lawn

Pink snow mold may be avoided by raking leaves and avoiding snow piles that extend through winter. These cultural practices will help limit the duration of conditions favorable for pink snow mold infection and spread during winter and fall months.

Apply Nutri-Lawn's Organics Plus Topdressing

Research has shown that applying high quality composts in the fall, after the lawns have gone dormant, reduces snow mold.

How to Do the Last Late Fall Mowing

When the turfgrass has gone dormant in the fall due to cool temperatures and shorter days, pull out the mower for one final cut.

Lower the normal mower cutting height about 3/4" to 1", and bag the clippings. This removes alot of the dead or damaged leaf material that accumulates over the summer. It also reduces the snow catching potential of the lawn, and reducing snow cover reduces disease.

Remember to raise the mower height back up before putting the mower away. The following spring, when you start to mow again, will result in the top 3/4" to 1" of grass will be new seasons growth. The lawn will be green and lush.

Avoid High Nitrogen Fertilizers in the Fall

We recommend using WInterizer Fertilizers that are high in potash. Potash strengthens the cell walls of turfgrass, and enhances the lawns ability to tolerate temperature extremes.
The nitrogren should be slow release to avoid causing the lawn to suddenly grow new succulent leaves.

Fungicide applications are not recommended for home lawns.

If you think you have a snow mold problem,
and need some help...

Contact a local Nutri-Lawn

We can repair snow mold damage
and have your lawn lookin g great!

We can also apply premium quality composts to help reduce overall disease incidence!