Snow Mold: Typhula Blight
Typhula blight, also known as gray snow mold or speckled snow mold, is most severe under extended periods of deep snow that covers a wet turfgrass on unfrozen soil. Phrases like “extended periods of snow cover” seem vague to a golf course superintendent. More specifically, you need at least 50 to 60 days of snow cover. The pathogen Typhula incarnata is most active when temperatures are 33 - 35F. Grayish to straw colored circular patches ranging from an inch to a yard in diameter appear at snow melt. A grayish mycelium may be present infected turf, which gives it the grayish or speckled look.
A Typhula incarnata sign is the presence of reddish to reddish brown sclerotia. In addition to Typhula incarnata, Typhula ishikariensis is a causal agent of Typhula blight. Typhula ishikariensis produces the same snow mold symptoms as Typhula incarnata but the pathogen never produces reddish sclerotia. The sclerotia produced are much smaller and tend to be dark brown to black in color.
Culturally, over fertilization in late fall in areas where Typhula blight is a serious chronic problem should be avoided. If turf growth is occurring under a snow cover, Typhula blight can occur rapidly if the snow remains for an extended period of time.
Fungicide applications should be made preventatively. When applying a fall fungicide treatment for Typhula blight apply it as close to the first snow fall as possible. Fungicides have a tendency to photodegrade when left exposed on the turf for an extended time. If symptoms appear in the spring, retreating for this disease is a waste of time.
Fungicides that are penetrants (absorbed through the leaf and into the plant) need to be applied prior to leaf growth ceases in the fall. Contact fungicides should be used in combination with a penetrant. Curative fungicide treatments are not effective in late winter or early spring. However, late winter treatments can speed spring recovery of infected turf.
There are various fungicides – mainly in combinations – that work for Typhula blight control. One that has performed well is the combination of a demethalation inhibitor (DMI) in combination with chlorothalonil. Syngenta provides Banner and Daconil or a premix of these in the product Instrata.
About the author
Dr. Karl Danneberger is a professor of Turfgrass Science at The Ohio State University. Dr. Danneberger's contact information can be found here. You may also follow Dr. Danneberger on Twitter: