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Gray Leaf Spot — Pyricularia grisea
© 2012 MSU Plant Pathology
© 2012 MSU Plant Pathology
© 2012 MSU Plant Pathology
Gray leaf spot is considered a problem on primarily perennial ryegrass and St. Augustinegrass. The disease first appears as tiny brown spots that enlarge and become oval or elongated. The mature spots usually have depressed gray centers with irregular brown margins, and a ring of chlorotic tissue surrounding. Severe infection shows burned or scorched blades of turfgrass. Lesions are also found on the leaf sheath, spike and stems. Stem lesions tend to be brown to black.
The disease is most severe during warm, humid weather. The pathogen overwinters as spores and dormant mycelium in the lower leaves of infected plants and thatch. When temperatures rise, the spores are spread by wind and water to healthy plants. Under conditions of high humidity and high temperature (80° to 90° F [26° to 32° C]), the disease may develop rapidly. Newly established stands of St. Augustinegrass are more susceptible to gray leaf spot than mature turfs.
Gray leaf spot is considered a problem on primarily perennial ryegrass and St. Augustinegrass. The disease first appears as tiny brown spots that enlarge and become oval or elongated. The mature spots usually have depressed gray centers with irregular brown margins, and a ring of chlorotic tissue surrounding. Severe infection shows burned or scorched blades of turfgrass. Lesions are also found on the leaf sheath, spike and stems. Stem lesions tend to be brown to black.
The disease is most severe during warm, humid weather. The pathogen overwinters as spores and dormant mycelium in the lower leaves of infected plants and thatch. When temperatures rise, the spores are spread by wind and water to healthy plants. Under conditions of high humidity and high temperature (80° to 90° F [26° to 32° C]), the disease may develop rapidly. Newly established stands of St. Augustinegrass are more susceptible to gray leaf spot than mature turfs.
Also Known As...
- Location:
» Home, Golf Course
- General Symptoms:
» Wilted, Irregular
- Foliar Symptoms:
» Spots, Brown
- Time of Year:
» Jun, Jul, Aug
- Irrigated:
» Yes, No
- Hosts:
» Perennial Ryegrass
Avoiding excessive nitrogen applications before and during the time of year when gray leaf spot is a problem can aide in suppression of the disease. Applying irrigation in the middle of the day will allow foliage to dry quickly and thus help reduce the severity of the disease.
Certain cultivars of St. Augustinegrass are more resistant than others; however, there seems to be no cultivars of perennial ryegrass resistant to gray leaf spot.
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- Chemical Control of Turfgrass Diseases 2011
University of Kentucky College of Agriculture
Perennial ryegrass and St. Augustinegrass
