Winter Turf Disease

Winter turf diseases
Winter diseases of turfgrasses are often associated with melting snow or cold, wet periods. Bluegrasses, fescues, and ryegrasses may all be attacked, but bentgrasses are most susceptible. Two diseases, Grey snow mold and Pink snow mold may occur singly or side-by-side. Since different fungicides may be used to control each of these diseases, it is necessary to distinguish between them.

Pink Snow Mold
Pink snow mold is a disease that may affect all cool-season turfgrasses, but appears to be most damaging to creeping bentgrass and annual bluegrass on golf courses. The disease is caused by a fungal pathogen, Microdochium nivale, that blights leaves but is not reported to affect roots and crowns.

On short-mown golf turf, pink snow mold symptoms include well-defined, circular patch clusters on creeping bentgrass greens, streaks of off-colored turf that follow the green’s surface drainage patterns may appear during the spring. During cool, wet conditions, white-pink mycelium may be observed on infected leaf blades Patches of dead, matted leaf blades also occur on taller mown turf, but often lack a clearly circular pattern. The temperatures that favor infection and spread range from 32˚F–50˚F. This pathogen often is very active through mid-spring.



Grey Snow Mold
Gray snow mold affects all cool season turfgrass species in areas where there are
extended periods of snow cover. The disease is caused by either of two Typhula species: Typhula incarnata and Typhula ishikariensis. T. ishikariensis infections may progress down into the crown, resulting in plant death or more severe and lasting damage. T. incarnata outbreaks are normally less severe, and infected patches tend to recover more quickly in the spring. In areas without prolonged snow cover, gray snow mold damage to turf
is largely cosmetic.

The gray snow mold fungi are active in a very narrow range of low temperatures (31˚F–36˚F). If snow cover exists for less than 45 days, then damage (symptom expression will be mild or negligible). If snow cover exists for 45–90 days, then moderate amounts of snow mold can be expected. If snow cover occurs for more than 90 days, then the risk of severe turf damage is high.

Management Strategies
Development of pink snow mold can be reduced by various cultural methods. Avoid late fall applications of fertilizer that would stimulate succulent growth. Such growth is very susceptible to infection. Also continue to mow turf as long as it continues to grow in the fall, and avoid compacting snow over the turf.

Fungicide applications should be made in late autumn / early winter just before permanent snow cover is expected and, if possible, during a mid-winter thaw. For putting greens, green surrounds,
and tees, a variety of fungicide mixtures that include two or three different products can be
quite effective. A DMI fungicide should be one component of the mixture. Other components
that have been used successfully include dicarboximides, strobilurins, and fludioxanil.
There are combination products on the market that have also been shown as very effective.
Call or check your local turf extension office for what is available in your area.

Where snow mold has caused damage, rake the matted grass in order to encourage new spring growth. If reseeding areas where the disease has been a problem, use disease resistant turfgrass varieties.