University of FloridaSolutions for Your Life

Download PDF
Publication #SS-AGR-38

Dollar Spot (Sclerotinia homoeocarpa) on Bahiagrass Pastures in North Florida1

A.R. Blount, W. Dankers, M.T. Momol, and T.A. Kucharek2

Dollar spot (Sclerotinia homoeocarpa, F.T. Benn) commonly causes leaf disease in turf grasses. Dollar spot can be a problem in pasture grasses in Florida, but normally, the fungus is not considered to be a continual problem in pastures where bahiagrass (Paspalum notatum Flugge) is the main pasture species. Two occurrences of dead bahiagrass pastures were attributed to dollar spot in Alachua County in 1990 and in the 1980s in Marion County (Gordon Prine, Forage Agronomist, Univ. of FL, personal communication), but documentation of these outbreaks was not published.

In spring and summer 2001, there was a severe outbreak of the disease on bahiagrass pastures in several counties in the Florida Panhandle (Figure 1). Normally, dollar spot first occurs in pasture situations in Florida during the summer rainy season, but not in the spring. Bahiagrass is generally considered to be a vigorous, well-adapted grass species in Florida with few reported disease problems. During the spring of 2001, a number of north Florida county Extension agents reported a scorched appearance on many bahiagrass pastures. Most often the pastures were planted in Tifton 9 or Pensacola cultivars, but several pastures were predominately Argentine bahiagrass. In early reports, symptoms ranged from mild tip burning of the leaves to significant leaf death and, in several cases, plant death. The presence of the fungus was confirmed on bahiagrass plant samples in Jackson, Washington, Gadsden, Leon, Walton, Calhoun and Gulf Counties, Florida. Damage attributed to the fungal outbreak ranged from 10% to 95% of leaf tissue (Figure 2). Severe cases in Jackson and Walton counties resulted in the death of the pastures, with surviving plants estimated at less than 5%. Leaves from bahiagrass plants infected with dollar spot were chlorotic, with lesions on the leaves and leaf margins exhibiting a scorched appearance (Figure 3). Mycelial growth was common at the crown of infected plants. Leaf symptoms of the fungus were visible throughout the growing season. Plants with early infection appeared chlorotic and death of infected plants was not uncommon. Bahiagrass varieties appeared to react differently to the disease pressure. Plants of cultivar Argentine had considerably less (10-20%) leaf damage than cultivars Pensacola and Tifton 9 (15-95%).

Environmental stresses during 2001 are likely to have contributed to the pasture deaths and general susceptibility of the pastures. Low soil pH and severe drought conditions, followed by heavy rains and warm, humid conditions were the most likely contributing factors in the severe outbreaks that occurred, particularly in Walton and Jackson Counties (Figure 4).

Figure 1. 

Bahiagrass pasture death attributed to dollar spot outbreak in north Florida.


[Click thumbnail to enlarge.]

Figure 2. 

Leaf symptoms on bahiagrass after moderate outbreak of dollar spot.


[Click thumbnail to enlarge.]

Figure 3. 

Leaf symptoms of dollar spot on bahiagrass.


[Click thumbnail to enlarge.]

Figure 4. 

Stroma of Sclerotinia homeocarpa isolated from a bahiagrass pasture in Walton County, Florida.


[Click thumbnail to enlarge.]

Footnotes

1.

This document is SS-AGR-38, one of a series of the Agronomy Department, Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida. Original publication date January 2002. Revised March 2006. Reviewed September 2012. Visit the EDIS website at http://edis.ifas.ufl.edu.

2.

A. R. Blount, assistant professor, W. Dankers, senior biological scientist, M.T. Momol, professor, and T. A. Kucharek, professor, Plant Pathology Department, Cooperative Extension Service, Institute of Food and Agricultural Sciences, Gainesville, FL 32611.


The Institute of Food and Agricultural Sciences (IFAS) is an Equal Opportunity Institution authorized to provide research, educational information and other services only to individuals and institutions that function with non-discrimination with respect to race, creed, color, religion, age, disability, sex, sexual orientation, marital status, national origin, political opinions or affiliations. For more information on obtaining other UF/IFAS Extension publications, contact your county's UF/IFAS Extension office.

U.S. Department of Agriculture, UF/IFAS Extension Service, University of Florida, IFAS, Florida A & M University Cooperative Extension Program, and Boards of County Commissioners Cooperating. Nick T. Place, dean for UF/IFAS Extension.