Typhula blight is a lawn disease related to the Typhula

Typhula

Typhula is a genus of clavarioid fungi in the order Agaricales. Species of Typhula are saprotrophic, mostly decomposing leaves, twigs, and herbaceous material. Basidiocarps are club-shaped or narrowly cylindrical and are simple , often arising from sclerotia. The anamorphic genus Sclerotium is a...

 fungus, usually caused by Typhula incarnata

Typhula incarnata

Typhula incarnata is, along with Typhula ishikariensis, the causal agent of Grey Snow Mould , a plant pathogen that can destroy turfgrass when covered for a long perioid with snow. It is a particular problem on golf courses established in unsuitable areas...

and T. ishikariensis. Snow molds are cold tolerant fungi that require snow cover or prolonged periods of cold, wet conditions. Typhula blight is most notably found in the turf industry, effecting a wide range of turfgrasses. Upon the snow melt, gray circular patches of mycelium are found. These mycelia produce a survival structure called a sclerotia that survives the warm summer months. Typhula blight is commonly controled with fungicide applications in the late fall and by other cultural practices. If unchecked, gray snow mold can cause severe turf loss.

Hosts and symptoms

Typhula blight is a major problem with cool season turfgrasses from December through April. These grasses include bentgrass, annual bluegrass, perennial ryegrass, fine fescue

Fescue

Festuce is a genus of about 300 species of perennial tufted grasses, belonging to the grass family Poaceae . The genus has a cosmopolitan distribution, although the majority of the species are found in cool temperate areas...

, and kentucky bluegrass. Typhula blight is also commonly referred to as gray snow mold due to the gray colored patches found after snow has melted. This disease is primarily found in the Great Lakes region which includes Minnesota, Wisconsin, Illinois, Indiana, Michigan, Ohio, Pennsylvania, and New York where winter temperatures can range from 30-40 degrees fahrenheit. Gray snow mold effects all of its hosts in the same way. After the snow has melted, gray to grayish white patches of mycelium

Mycelium

thumb|right|Fungal myceliaMycelium is the vegetative part of a fungus, consisting of a mass of branching, thread-like hyphae. The mass of hyphae is sometimes called shiro, especially within the fairy ring fungi. Fungal colonies composed of mycelia are found in soil and on or within many other...

, six to twelve inches in diameter, can be found. Within the patches, diseased grass blades often reveal either rust or reddish brown colored sclerotia up to five millimeters in diameter. Gray snow mold can cause thinning and possibly death of the infected host.

Disease cycle

Unlike most plant pathogens, Typhula blights dormant stage occurs in the warm conditions of the summer months as sclerotia, a hard survival structure. Upon favorable conditions of cold, wet weather, the sclerotia germinates grayish white spore-bearing bodies called sporocarps or hyphae with clamp connections. The disease then infects the plant tissue and resumes the disease cycle. It is there where the pathogen produces sclerotia to survive the next summer months.

Environment

Typhula blight is commonly found in the Great Lakes region where fall and winter temperatures can range between 30-40 degrees fahrenheit. The disease is usually dependent on 60 days of snow cover and high nitrogen fertility where the ground has yet to freeze. Disease growth is also favored by excessive thatch, poor drainage and high soil moisture. Typhula blight also prefers uncut or taller grass that has been matted down. This is because tall grass can provide an incubation chamber underneath the snow fall, promoting fungal growth of snow molds.

Management

Gray snow mold can be controlled by fungicide applications. However, the timing of the application is crucial. This chemical treatment needs to be done in late fall before the first snow fall. If the application is made too soon a second follow up treatment may be needed. Possible chemical applications include: a demethalation inhibitor, or DMI, with a chlorothalonil product, a DMI with a thiophanate-methyl product, or a Iprodione with a chlorothalonil product. Typhula blight can also be controlled culturally. One method would be to plant a less susceptible turfgrass. Bentgrass and annual bluegrass are the two most susceptible turfgrasses to Typhula blight. Another method is to limit heavy late season fertilizer applications. Finally, cutting the grass until dormancy to keep the grass height down can help.

Importance

Typhula blight is a very common disease in the Great Lakes region and Intermountain Northwest that can have detrimental effects in the spring. This is a very important disease because if the proper precautions are not taken, turfgrass can be lost.