7/2/2013 - By Harrell's

Spring Dead Spot[Ophiosphaerella korrae & Ophiosphaerella herpotricha]

Excerpt from an article by NC State University

Symptoms

Circular patches of bermudagrass, from 6 inches to several feet in diameter, remain dormant as the turf greens up in the spring. These patches eventually die and collapse to the soil surface. The roots, stolons, and rhizomes are dark and rotten in affected areas. Spring dead spot patches recur in the same spot yearly and increase in size by up to several inches each season. As the patches expand, the centers are sometimes re-established with bermudagrass or weedy species, resulting in a ring-like appearance. Recovery of the patches occurs by spread of the bermudagrass from the outside. This process is very slow, taking the entire growing season in severe situations. The spring dead spot patches greatly detract from the uniformity of the playing surface and are frequently invaded by weeds. Spring dead spot may also occur in certain varieties of zoysiagrass, such as ‘Meyer’ and ‘El Toro’.

Factors Affecting Disease Development

Spring dead spot is most evident on intensely managed bermudagrass, such as athletic fields and golf courses. The disease typically takes 3 to 5 years to become established in a new bermudagrass stand. Unlike take-all patch, spring dead spot does not decline in severity as the turf matures. It becomes more severe if left unmanaged.

The spring dead spot fungus attacks the roots, rhizomes, and stolons of bermudagrass during the fall and winter. This activity does not directly kill the plant, but instead makes the bermudagrass more susceptible to freezing injury. As a result, spring dead spot is most severe in the northern range of bermudagrass adaptation and is usually more severe after extremely cold winters.

Spring dead spot is most severe when soil pH is 6.5 or greater. In addition, any factor that restricts bermudagrass root growth or increases its susceptibility to winter injury will also enhance the disease. Excessive nitrogen, potassium deficiencies, poor soil drainage, over-irrigation, excessive thatch accumulation, and soil compaction have been shown to encourage disease development.

Continue this article at the NC State TurfFiles web site