Pythium-Induced Root Dysfunction of Secondary Roots of Agrostis palustris. Clinton F. Hodges, Professor of Horticulture and Plant Pathology, Department of Horticulture, Iowa State University, Ames 50011. L. W. Coleman, Postdoctoral Research Associate, Department of Agricultural Biochemistry, University of Nebraska, Lincoln 68583-0718. Plant Dis. 69:336-340. Accepted for publication 18 October 1984. Copyright 1985 The American Phytopathological Society. DOI: 10.1094/PD-69-336.

Pythium aristosporum and P. arrhenomanes are reported as new pathogens of the secondary roots of Agrostis palustris grown on golf green mixes with a high sand content. P. vanterpoolii also was found associated with the roots but was not pathogenic. The total, shoot, and root dry weights of plants root-inoculated with P. aristosporum and P. arrhenomanes decreased in sand and to a lesser extent in sand-loam media. Both pathogens developed throughout the cortical and vascular tissues of the roots but did not produce lesions or rot. Infected roots occasionally had a light buff coloration. Mycelium was observed in root hairs, and infected root tips were bulbous and ultimately devitalized. Sporangia and oospores were rarely observed in infected roots.