Gray Leaf Spot of Perennial Ryegrass

Fig. 2. (a) Distortion of the leaf blade at the point of infection leads to a twisted appearance. Blighting and twisting from the tip of the leaf blade results in the “fish hook” symptom. (b, shown here) After extended periods of high relative humidity and temperatures between 25 and 28°C, profuse sporulation results in a gray felt-like growth associated with leaf spots and blighted leaf blades.



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