Snow mold

Snow Mold Damage Revealed by Melting Snows

Melting snows have uncovered significant snow mold damage. There are two types of diseases to be aware of: gray and pink. Although they produce similar symptoms, the pathogens differ and require different temperature ranges for infection.

Gray Mold: Occurrence and Control

Gray pathogen infects within a narrow temperature range (32 – 36 degrees Fahrenheit). Snow cover’s insulation maintains these temperatures at the turf surface. Gray, while not common in Indiana, appears where snow piles linger all winter. The pathogen forms survival structures called sclerotia, about the size of a printed period. At this time of year, controlling gray mold focuses on hastening patch recovery. Since infection requires a narrow temperature range, it won’t spread further this year. Disturbing the matted turf by raking and applying a light dose of nitrogen can speed up turf growth as temperatures rise, mitigating the disease’s effects.

Pink Mold: Prevalence and Management

Pink is more prevalent in the lower Midwest, infecting at temperatures between 32°F and 50°F. Symptoms developing after snow melts in cold, wet spring weather are due to the Microdochium patch phase of the disease. The pathogen produces spores at the edges of circular patches, which may spread downslope, particularly on putting greens. Young creeping bentgrass is particularly susceptible to snow mold damage.

Strategies for Treating Pink Snow Mold

As pink  mold remains a threat through April and May, treatment strategies differ. Fungicides might not be necessary for fairways, but I recommend considering their use on tees and putting greens if many patches developed over the winter. Disease progress thins turf within the patches, making it prone to Poa annua colonization. A contact fungicide like chlorothalonil can limit spread while the turf is dormant. Once the turf starts growing actively, a penetrant fungicide, such as a DMI, might offer more effective control.

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