SPRING DEAD SPOT

spring dead spot root and stolon rot	Characteristic	Description
	Host Grass Species	bermudagrass, zoysiagrass
	Month(s) with symptoms	April to September
	Stand Symptoms	spots, circles, patches (6 inches to greater than 3 feet), rings
	Foliar Symptoms - Location/Shape	blighting of entire leaves
	Foliar Symptoms - Color	tan, yellow, orange
	Root/Crown Symptoms	roots, stolons, rhizomes, and/or crowns dark brown or black
	Fungal Signs	none

 

Note: Still not sure if this is the right disease? The Turfgrass Disease Identification program may be helpful. Or consult the experts at the Turf Diagnostics Lab. Check the TurfFiles glossary for definitions of unfamiliar terms.

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. 

CULTURAL CONTROL

Maintain soil pH between 5.5 and 6.0 to minimize spring dead spot development. Soil pH is best reduced slowly over time through use of an acidifying nitrogen source, such as ammonium sulfate or sulfur coated urea. Fertilize to meet the nutritional needs of the turf, but do not apply excessive rates of nitrogen. Do not apply nitrogen within 6 weeks of winter dormancy, and do not exceed more than 1 pound of nitrogen per 1,000 square feet per application at any time during the growing season. Apply potassium (1 pound K₂O per 1,000 square feet) and raise the mowing height to 1 or 1.5 inches in late summer to improve the winter hardiness of the bermudagrass.

Reduce thatch buildup and relieve soil compaction through aggressive aerification and vertical mowing. Areas that are severely affected by spring dead spot should be hollow-tine aerified at least three times per year, during the summer when bermudagrass is most actively growing. Golf greens should also be topdressed along with aerification to control thatch accumulation.

Once the symptoms of spring dead spot appear, the only means of control is to encourage the spread of bermudagrass into the affected patches. Frequent spiking or aerification is recommended to break up the mat of dead turf in affected patches. Applying extra nitrogen to encourage recovery is not recommended, as this can enhance the disease in the following year.

Dinitroaniline (DNA) herbicides, which are commonly used for preemergent control of annual grasses, can slow the recovery of bermudagrass from spring dead spot injury and should not be used in sites with a history of the disease. 

CHEMICAL CONTROL

Fungicides are available for spring dead spot control, but they must be applied preventatively in the fall. Fenarimol has been the most effective and consistent fungicide for spring dead spot control. Applications are most effective when soil temperatures are between 60 and 80°F. To move the fungicide into the root zone, apply in a high volume of water (5 gallons per 1,000 square feet) or water in with ¼” of irrigation immediately after application. Repeat applications at high label rates may be necessary in severely affected areas. Affected areas should be mapped in the spring for treatment in the fall to reduce fungicide expenditures.

© North Carolina State University. This information sheet was prepared by Lane P. Tredway, Gail G. Wilkerson, Bridget R. Lassiter, Jenifer J. Reynolds, and Gregory S. Buol. Departments of Plant Pathology and Crop Science, College of Agriculture & Life Sciences, North Carolina State University. Prepared April 29, 2008. Available on-line at www.turffiles.ncsu.edu. This publication was made possible through a grant provided by the Center for Turfgrass Environmental Research & Education (CENTERE) whose purpose is to support worthwhile projects that will benefit both the private sector and the public, and protect the environment.