Dollar Spot

Disease Background

Sclerotinia homoeocarpa

Dollar spot is a fungal disease which affects cool season grasses, including browntop bent (Agrostis capillaris), creeping bent (Agrostis stolonifera), red fescues (Festuca rubra spp.), smooth-stalked meadowgrass (Poa pratensis) and annual meadowgrass (Poa annua). Dollar spot is most prevalent during warm, humid conditions (prolonged wet foliage), particularly following on from a period of hot, dry conditions. Dollar spot incidence has also been recorded with night temperatures as low as 70C. The severity of the infection will depend upon the virulence of the fungus and the susceptibility of the grass plant (stress factors or improved tolerance).


The significance of disease tolerance in grass breeding

There are significant differences in tolerance to dollar spot between individual cultivars within a species. Cultivar selections from the breeding programme are deliberately infected with dollar spot, both in the laboratory climate rooms and in field trials. In addition, dollar spot is also allowed to occur naturally in field trials in order to have a comprehensive picture of a particular cultivar’s tolerance. Graph 1 shows the survival and recovery of cultivars of slender creeping red fescue (Festuca rubra trichophylla) and Chewings fescue (Festuca rubra commutata) recorded in trials at Barenbrug Research, showing Barswing, Bargreen II and Barcrown to have superior tolerance. Graph 2 shows the level of infection recorded in red fescue and fine-leafed sheep’s fescue (Festuca ovina tenuifolia).