IPM Identification and Mangement Of Turfgrass Diseases
Gray Snow Mold
(speckled snow mold)
(speckled snow mold)
Pathogen: Typhula spp.
Hosts: Most cool-season turfgrasses
Yellow to white circular patches of damaged turf are visible immediately following snow melt(Figure 1). These patches vary in size and may overlap to blight almost the entire turf stand(Figure 2). White to gray fungal mycelium may still be evident on diseased leaves, especially on higher cut turf, but will eventually dry out and disappear (Figure 3). As the damaged leaves begin to wither, the patches develop more of a white to gray color (Figure 4).The observation of clamp connections at high magnification and sclerotia embedded in infected leaf tissue are diagnostic for gray snow mold. Clamp connections are “bridges” from one hyphal cell to another (Figure 5). The sclerotia are initially white to pink or orange, but harden and turn dark brown to black with age(Figure 6). The mature sclerotia range in size up to 0.2 inch in diameter.
Damage in home lawns and golf course fairways is often cosmetic. The turfgrass quickly recovers and resumes normal growth with the return of warm spring weather. However, damage to annual bluegrass and creeping bentgrass on putting greens and other closely mowed areas may be more extensive and spring recovery slower.
Gray snow mold fungi are widely distributed in regions with long periods of snow cover. There are several species of Typhula, and their abundance in a particular location is governed in part by the length of snow cover. T.ishikariensis tends to be more prevalent in areas with long periods of snow cover, whereas T.incarnata is more common where snow cover periods are shorter.
These fungi persist through the summer as hardened sclerotia. In late fall, sclerotia germinate and begin to colonize the grass leaves. In some cases sclerotia may germinate to form fruiting structures (basidiocarps) that in turn produce spores (basidospores) that help disseminate the fungus and initiate disease.
The growth of Typhula spp. is favored by temperatures near freezing (32 to 36°F). Thus, long periods of snow cover that help maintain temperatures at the soil surface just above freezing are ideal for fungal growth. The longer snow cover remains, the more extensive are the fungal colonization of the turfgrass and subsequent damage.
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.
