Cause of Pythium Root Dysfunction
By Troy Taylor
A Class Project for PP728: Soilborne
North Carolina State University
Department of Plant Pathology
Introduction: Pythium volutum is the causal agent of Pythium root dysfunction on turf in the southeastern United States (2). In the upper midwest this disease was shown by Hodges (4) in 1985 to be caused by Pythium arrhenomanes, P. aristosporum and P. vanterpoolii. Pythium volutum was first associated with Pythium root dysfunction in 2002 in North Carolina. At first the disease was diagnosed by many in the southeast as take-all patch caused by Gaeumannomyces graminis. But isolation of this pathogen from infected turf proved unsuccessful. Further evaluation of the infected root systems revealed an abundant mass of Pythium oospores and hyphae. This fungus was later identified as Pythium volutum (2).
|Host range and distribution: Pythium volutum infects creeping bentgrass putting greens in the southeastern United States. It is most damaging to greens constructed within the last 10 years. Creeping bentgrass existing at optimum growing conditions is much more resistant to the disease than poorly managed turf. Pythium volutum has been isolated from creeping bentgrass in Virginia, North Carolina, South Carolina and Georgia. It has also been isolated from oats in Canada, the Netherlands, and England. It has been reported on both marsh horsetail and western dock in Poland and Pyhtium volutum has also been isolated from common wheat in the United States (5).|
Figure 1: Pythium volutum symptoms and root cross section
Isolation: Isolation of Pyhtium volutum can be done directly from infected roots by plating on V8 agar. A more popular method and perhaps more successful is isolation by baiting onto creeping bentgrass leaf blades (2). Leaf blades are then transfer to V8 agar to obtain culture.
Figure 2: Close up of roots infected with Pythium volutum
Identification: Isolates should be transferred to grass leaf blade cultures to induce sporangia, oospore and antheridia production (2). Isolates of P. volutum produce both lobulate sporangia and relatively large oospores measuring 27 to 33 um long and 2.8 um wide. Isolates are also characterized by production of three to nine diclinous antheridia.
Figure 3: Microscopic features of P. volutum Figure 4: Microscopic view of roots infected with P. volutum
Symptoms: Pythium root dysfunction appears in circular or irregular patches up to two feet in diameter, which initially display signs of wilt or nutrient deficiency. Infected turf then turns orange or yellow as dieback from the leaf tip begins and eventually the turf collapses. Root tips of infected turf are bulbous. The roots are completely void of root hairs and have a loose cortical structure. Reductions in both root mass and depth of root system can be seen in both the fall and the spring but roots begin to die back rapidly when soil temperatures reach higher than 85 degrees Fahrenheit.
Figure 5: Pythium volutum symptoms Figure 6: Pythium volutum symptoms
Ecology and life cycle: Pythium volutum is believed to infect creeping bentgrass turf species in the fall and spring when soil temperatures are between 50 and 75 oF. The disease is favored by both low fertility and drought stress, however wet soils are important for P. volutum to cause an initial infection. While initial infection in the southeastern United States occurs in the spring or fall symptoms of the disease aren’t readily seen until the summer.
1. Tredway, Lane P., and James P. Kerns Aug. 2005. Defining the Nature of Creeping Bentgrass Root Disease. 13 Nov. 2008
2. Kerns, James P., and Lane P. Tredway 28 Jan. 2008 First Report of Pythium Root Dysfunction of Creeping Bentgrass Caused
Pythium Volutum in North Carolina. 13 Nov. 2008 http://www.apsnet.org/pd/searchnotes/2007/PDIS-91-5-
3. Tredway, Lane P 3 Nov. 2008. Pythium Root Dysfunction. 13 Nov. 2008
4. Hodges, Clinton F. 1985. Pythium- Induced Root Dysfunction of Creeping
Bentgrass on High Sand Content Greens. 13 Nov. 2008
5. Farr, D.F., & Rossman, A.Y. Fungal Databases, Systematic Mycology and
Microbiology Laboratory, ARS, USDA. Retrieved December 1, 2008, from
6. Hodges CF. 1985. Pythium-Induced Root Dysfunction of Secondary Roots of Agrostis
palustris. Plant Disease 69:336-40.
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