Typhula blight

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Typhula blight
Causal agents Typhula incarnata , Typhula ishikariensis


Typhula blight (commonly called gray snow mold or speckled snow mold) is most commonly known as a turf disease, but can also be a problem with wheat. Typhula blight is caused by a Typhula fungus, either Typhula incarnata or T. ishikariensis . Typhula incarnata is the causal agent for gray snow mold and T. ishikariensis causes speckled snow mold. [1] Snow molds are caused by cold tolerant fungi that require snow cover or prolonged periods of cold, wet conditions. Typhula blight is most notably found in the turf industry, affecting 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. [2] Typhula blight is commonly controlled with fungicide applications in the late fall and by other cultural practices. [3] If unchecked, snow molds can cause severe turf loss.

Contents

Hosts and symptoms

Typhula blight is a major problem with cool season turfgrasses during winter months. These grasses include bentgrass, annual bluegrass, perennial ryegrass, fine fescue, and kentucky bluegrass. [1] Typhula blight is also commonly referred to as gray snow mold due to the gray colored patches found after snow has melted. Gray snow mold affects all of its hosts in the same way. After the snow has melted, gray to grayish white patches of mycelium, six to twelve inches in diameter, can be found. [1] Within the patches, diseased grass blades often reveal either rusty or reddish brown colored sclerotia up to five millimeters in diameter. Gray snow mold can cause thinning and possibly death of the infected host. [2]

Disease cycle

Unlike most plant pathogens, Typhula blight's dormant stage occurs in the warm conditions of the summer months as sclerotia, a hard survival structure. [4] Upon favorable conditions of cold, wet weather, the sclerotia germinates grayish white spore-bearing bodies called basidiocarps to produce 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. [4] [5]

Environment

Typhula blight is commonly found in United States in the Great Lakes region [2] and anywhere where cold winter temperatures and snow fall persist. 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, promoting fungal growth of the snow mold. [3]

Management

Typhula blight and snow molds can be controlled by fungicide applications. [6] 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 demethylation inhibitor, or DMI, with a chlorothalonil product, a DMI with a thiophanate-methyl product, or an Iprodione with a chlorothalonil product. [6] 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. [7]

Importance

Typhula blight is a very common and damaging disease of the Great Lakes [2] and Intermountain Northwest [3] regions of the United States. Millions of dollars are spent each year to prevent this disease from occurring. Typhula blight, although serious and detrimental, with proper precautions can be avoided. For many homeowners, typhula blight will show up in the spring on their lawns. Because this disease does not always kill the grass, the lawn can green-up very quickly, avoiding a decline in aesthetics. However, for many golf courses, these brown patches early in the season are not tolerable. Although the turf may green-up eventually, in the turf industry where aesthetics are valued highly, typhula blight must be evaded.

See also

Related Research Articles

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<span class="mw-page-title-main">Brown patch</span> Fungal disease affecting turfgrasses

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<span class="mw-page-title-main">Brown ring patch</span> Fungal disease of turf grass

Brown ring patch is a recently described Rhizoctonia-like disease of turf grass caused by the fungus Waitea circinata var. circinata. The disease primarily affects putting greens and causes yellow or brown rings up to 1 metre (3.3 ft) in diameter. Brown ring patch was first observed in Japan and has since spread to the United States and China (2011).

Bacterial wilt of turfgrass is the only known bacterial disease of turf. The causal agent is the Gram negative bacterium Xanthomonas translucens pv. graminis. The first case of bacterial wilt of turf was reported in a cultivar of creeping bentgrass known as Toronto or C-15, which is found throughout the midwestern United States. Until the causal agent was identified in 1984, the disease was referred to simply as C-15 decline. This disease is almost exclusively found on putting greens at golf courses where extensive mowing creates wounds in the grass which the pathogen uses in order to enter the host and cause disease.

Necrotic ring spot is a common disease of turf caused by soil borne fungi that mainly infects roots (4). It is an important disease as it destroys the appearance of turfgrasses on park, playing fields and golf courses. Necrotic Ring Spot is caused by a fungal pathogen that is an ascomycete that produces ascospores in an ascocarp (6). They survive over winter, or any unfavorable condition as sclerotia. Most infection occurs in spring and fall when the temperature is about 13 to 28 °C (5). The primary hosts of this disease are cool-season grasses such as Kentucky bluegrass and annual bluegrass (6). Once turf is infected with O. korrae, it kills turf roots and crowns. Symptoms of the disease are quite noticeable since they appear as large yellow ring-shaped patches of dead turf. Management of the disease is often uneasy and requires application of multiple controls. The disease can be controlled by many different kind of controls including chemicals and cultural.

Gray leaf spot (GLS) is a foliar fungal disease that affects grasses. In grasses other than maize it is caused by Pyricularia grisea, which only infects perennial ryegrass, tall fescue, and St. Augustine grass in places with warm and rainy climates.

The annual bluegrass weevil, scientific name Listronotus maculicollis, is a turfgrass insect pest which feeds mainly on annual bluegrass. They prefer to feed on very low mown grass, and are thus found mostly on golf courses or grass tennis courts. ABWs, as they are often referred to, were only found in the Northeastern United States until the 2000s when sightings began to expand. In recent years they have been found as far north as Ontario and Quebec, as far west as Ohio, and as far south as North Carolina. Their choice of hosts has also expanded, and they have been reported feeding on perennial ryegrass and creeping bentgrass.

References

  1. 1 2 3 "RPD No. 404 – Snow Molds of Turfgrasses". Univ. of Illinois Extension. July 1997. Retrieved November 11, 2011.
  2. 1 2 3 4 Kerns, J.P. (2011). "Turf diseases of the Great Lakes region" (PDF). Univ. of Wisconsin Extension. Retrieved November 11, 2011.
  3. 1 2 3 Johnston, William H. (December 2003). "Snow Mold Control in the Intermountain Northwest" (PDF). U.S. Golf Association. Retrieved November 10, 2011.
  4. 1 2 Lamey, H. Arthur (July 1996). "Lawn Diseases PP-950". North Dakota State University. Retrieved November 10, 2011.
  5. ↑ Kennelly, Megan (February 2011). "Snow molds". Kansas State Univ. Extension. Archived from the original on April 25, 2012. Retrieved November 11, 2011.
  6. 1 2 Dale, Don (January 2010). "Controlling Typhula Blight". Turf Magazine. Archived from the original on April 6, 2012. Retrieved November 10, 2011.
  7. ↑ Franc, Gary D. (April 1998). "Snow molds of turfgrass B-868" (PDF). Univ. of Wyoming Extension. Archived from the original (PDF) on April 25, 2012. Retrieved November 11, 2011.

Chang, S. W., Scheef, E., Abler, R. A. B., Thomson, S., Johnson, P., and Jung, G. 2006. Distribution of Typhula spp. and Typhula ishikariensis varieties in Wisconsin, Utah, Michigan, and Minnesota. Phytopathology 96:926–933.

Chang, S. W., Chang, T. H., Tredway, L., and Jung, G. 2006. Aggressiveness of Typhula ishi- kariensis isolates to cultivars of bentgrass species (Agrostis spp.) under controlled environment conditions. Plant Dis. 90:951–956.

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