Causal Agent:
Pyricularia grisea
Susceptible Turfgrasses:
Perennial ryegrass
Tall fescue
Kikuyugrass
St. Augustinegrass
Identification:
Symptoms of Gray Leaf Spot vary depending on the turfgrass type:
Perennial Ryegrass and Tall Fescue:
Gray lesions on the leaves surrounded by yellow halos.
Leaves may exhibit twisted tips.
Warm-Season Grasses (Kikuyugrass, St. Augustinegrass):
Small brown spots that gradually enlarge.
Spots develop purple or brown borders as the disease progresses.
In severe cases, infected turf can take on a gray, drought-like appearance and experience rapid collapse.
Favorable Conditions:
Gray Leaf Spot typically thrives during the following conditions:
Timing:
Most common between mid-summer and late autumn.
Weather Conditions:
Extended heat and drought stress during late summer.
Additional Risk Factors:
In Perennial Ryegrass, Gray Leaf Spot can develop under colder conditions in late fall.
The disease poses significant damage risks to St. Augustinegrass and Kikuyugrass when conditions are favorable.
Management Tips:
Water Management:
Water deeply and infrequently to reduce drought stress. Avoid late-evening irrigation to limit prolonged leaf wetness.
Proper Fertilization:
Maintain balanced nutrient levels to avoid excessive nitrogen, which can increase susceptibility.
Thatch Control:
Aerate and dethatch regularly to improve air circulation and reduce disease risk.
Mowing Practices:
Keep blades sharp and avoid mowing wet grass to minimize spreading the pathogen.
