GRAY LEAF-SPOT OF PERENNIAL RYEGRASS TURF IN PENNSYLVANIA

A severe foliar disease of unknown etiology occurred on perennial ryegrass (Lolium perenne) turf during the summer of 1991 in southeastern Pennsylvania. Symptoms began as small brown lesions and rapidly progressed to a foliar blight on both seedling and mature perennial ryegrass. Isolation from diseased leaf tissue yielded a high percentage of Pyricularia grisea colonies. Inoculation of 4- and 20-wk-old plants resulted in symptoms very similar to naturally infected perennial ryegrass. Plants 4 wk old were more severely diseased than 20-wk-old plants, and necrosis of leaf tissue was more extensive at 29 C than at 22 C. P. grisea was consistently isolated from inoculated plants. Given the results of this study, it was concluded that P. grisea was the primary cause of the foliar blight that occurred in Pennsylvania. Gray leaf spot was chosen as the name of this disease.