Control of Yellow Ring in Kentucky Bluegrass Swards. H. T. Wilkinson, Assistant Professor of Plant Pathology, Department of Plant Pathology, University of Illinois, Urbana-Champaign 61801. . Plant Dis. 72:137-139. Accepted for publication 15 July 1987. Copyright 1988 The American Phytopathological Society. DOI: 10.1094/PD-72-0137.

Trechispora alnicola is the causal agent of yellow ring of Poa pratensis. In culture, isolates collected from the same diseased pieces of sod or from different swards did not grow or produce conidia after the two thalli intersected. Transplantation of diseased sod to cultivated soil or inoculation of symptomless field sod with plugs of diseased sod failed to develop yellow ring after 3 yr. Twenty-one cultivars of P. pratensis were susceptible to infection by T. alnicola, but 10 of these cultivars showed low disease ratings. In addition, 50 of 89 bluegrass selections and crosses showed less disease. Bluegrass mixtures consisting of two to five cultivars developed severe yellow ring in the field. Agrostis palustris, Festuca rubra, and Lolium perenne were not susceptible to infection by T. alnicola. The chemical PCNB (6.1 kg/ha) prevented the effective dissemination of T. alnicola and limited the severity of yellow ring in sod but did not eliminate disease symptoms. The fungicide propiconazole (6.1 kg/ha) reduced both the occurrence of new infections and disease severity but was less effective than PCNB.