Gray Leaf Spot of Perennial Ryegrass

Fig. 7. (a, shown here) Gray leaf spot symptoms can become severe on golf course roughs not protected with fungicides. (b) If fungicide protection lapses on golf course fairways, gray leaf spot can quickly spread to blight and kill large areas of perennial ryegrass.



Image from Plant Health Progress article:
Gray Leaf Spot of Perennial Ryegrass