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. The pathogen Typhula incarnata is most active when temperatures are 1-2 C. Grayish to straw colored circular patches ranging from 2.5 cm to 1 meter 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 symptoms; however it 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.
Fungicide applications should be made preventatively. 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. Fungicide selection is important because differences exist in control efficacy for Typhula incarnata and Typhula ishikariensis.