Gray Leaf Spot

Gray leaf spot is a fungus disease that affects several turfgrasses. It is a mainly a problem on St. Augustinegrass and perennial ryegrass. Hot humid summer weather and high nitrogen levels can make turf susceptible to this disease.

Information taken from Turfgrass Diseases in Georgia: Identification and Control

found at http://pubs.caes.uga.edu/caespubs/pubcd/B1233/B1233.html For more information or photos of the disease - see this publication.

Fungus Causing the Disease: Pyricularia grisea

Susceptible Turfgrass: St. Augustinegrass, Perennial ryegrass, Bermudagrass, Centipedegrass, Bentgrass and various species of Fescue

Symptoms: The symptoms of gray leaf spot vary depending on the grass cultivar. On St. Augustinegrass, gray leaf spot first appears as small, brown spots on the leaves and stems. The spots quickly enlarge to approximately ¼ inch in length and become bluish-gray in color and oval or elongated in shape. The mature lesions are tan to gray in color and have depressed centers with irregular margins that are purple to brown in color. A yellow border on the lesions can also occur. In cool-season turfgrass, the symptoms are similar to those of melting-out.

Conditions Favoring Disease: Gray leaf spot is favored by daytime temperatures between 80ºF to 90ºF and night temperatures above 65ºF. It is also found in areas with high nitrogen levels and that are stressed by various factors, including drought and soil compaction. This disease is most severe during extended hot, rainy and humid periods.

Disease Management Tips:

• Avoid medium to high nitrogen levels during mid-summer.
• Irrigate turf deeply and as infrequently as possible to avoid water stress.
• Allow water to remain on leaves for only a short period of time.
• Reduce thatch by vertical cutting.
• When possible, plant turfgrass that is resistant to gray leaf spot.
• Avoid using herbicides or plant growth regulators when the disease is active.
• Fungicides are available to control the disease. Consult the current Georgia Pest Management Handbook -- www.ent.uga.edu/pmh/.

 Please share this information with others in the landscape & turf industry. For more information:

Call your local Extension Agent at (800) ASK-UGA1 or locate your local Extension Office at http://www.caes.uga.edu/extension/statewide.cfm

Guide to Turfgrass Fungicides - http://pubs.caes.uga.edu/caespubs/pubcd/B1316/B1316.html

Turfgrass Diseases Quick Reference Guide - http://pubs.caes.uga.edu/caespubs/pubcd/C891/C891.html

Georgia Turf website - www.georgiaturf.com

Pest Management Handbook (Follow all label recommendations when using any pesticide) - www.ent.uga.edu/pmh/