Common Name: gray leaf spot
Scientific Name: Pyricularia grisea

Gray leaf spot initially appears as spots on the leaves that are round or oval, tan in color, and have a dark brown border. When the leaves are wet or humidity is high, the leaf spots turn gray and fuzzy with profuse spore production. In time, the leaf spots expand and girdle the leaf, causing it to die back from the tip. Significant damage to the turf stand may occur as the disease continues to progress. In tall fescue and perennial ryegrass, foliar blighting initially occurs in patches from 6 to 12 inches in diameter that are orange to yellow in color. Like the leaf spots, these patches rapidly coalesce to produce large, irregular areas of damaged turf. The leaves of tall fescue and perennial ryegrass blighted by gray leaf spot are typically matted and greasy in appearance. Because of this symptom, gray leaf spot is often confused with Pythium blight in tall fescue and perennial ryegrass. Gray leaf spot does not develop in distinct patches in St. Augustinegrass, but affected leaves may wither and die, causing a brown cast to the stand that is visible from a distance.
gray leaf spot leaf lesions
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Characteristic Description
Host Turfgrass (22)tall fescue, perennial ryegrass, and St. Augustinegrass
Month(s) with symptomsJuly, August, September
Stand Symptoms (12)spots, patches (4 to 12 inches)
Foliar Symptoms - Location/Shape (12)round or oval leaf spots
Foliar Symptoms - Color (12)tan, gray
Root/Crown Symptomsnone
Fungal Signs (1)none or fuzzy spore masses
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