Thursday, October 25, 2007

Turf - Pink Snow Mold

A common winter disease of turfgrass in Delaware is Pink Snow Mold. The following is an article on this disease.

Winter diseases of turfgrasses are often associated with melting snow or cold, wet periods. Bluegrasses (Poa sp.), fescues (Festuca sp.), and ryegrasses (Lolium sp.) may be attacked, but bentgrasses (Agrostis palustris) are most susceptible. Two diseases, Gray Snow Mold (Typhula Blight) and Pink Snow Mold, are common and 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.


The fungus that causes Pink Snow Mold produces roughly circular bleached patches up to 60 cm in diameter. Often the mycelium of the fungus is readily visible. In contrast to Gray Snow Mold, however, a pinkish cast to the symptomatic area might be observed under wet conditions. Moreover, no tan sclerotia are associated with the diseased plant tissue as seen in Gray Snow Mold. This disease can become severe when turf is subjected to prolong periods of cool, wet weather from early autumn to late spring, and does not require snow cover to develop. A severe infection by M. nivale kills the turfgrass.

Disease Cycle

The fungus Microdochium nivale survives unfavorable periods as dormant mycelium in infected plants and plant debris. As conditions improve for fungal growth, the fungus may begin to infect plants with little symptom development. Wet weather conditions with temperature around 16oC will promote rapid spread of the disease. Dry, warm weather causes the fungus to revert to its dormant state. The fungus can be transmitted throughout the year on equipment, people, animals, wind or water.

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 lawn. 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. If pink snow mold has been severe or wide-spread in past years, or if susceptible varieties or species are being grown, a preventative fungicide program may be used. Fungicide applications should be made in late autumn before permanent snow cover is expected and, if possible, during a mid-winter thaw.

Apply Banner, Chipco 26GT, chlorothalonil, Compass, ConSyst, Eagle, Heritage, Insignia, Medallion, PCNB, Spectro, thiophanate-methyl, or vinclozolin. Do not, however, reapply PCNB after January 15 due to the possibility of phytotoxicity during warm weather next spring.

Extracted and modified from "PINK SNOW MOLD ON TURFGRASS, Microdochium nivale" from the Cornell University Plant Disease Diagnostic Clinic factsheet.

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