Gray Leaf Spot: Identification and Treatment in Georgia
Gray leaf spot targets St. Augustine and bermuda during hot, humid summers. Learn how proper timing and treatment keep your lawn from thinning out.
Disease profile
What Is Gray Leaf Spot?
Gray leaf spot primarily attacks St. Augustine grass but also hits bermuda and other warm-season turf during hot, humid Middle Georgia summers. It starts as small lesions on individual blades and can quickly thin the lawn if conditions stay wet. Newly established lawns and recently fertilized turf are especially at risk.
Symptoms
How to Identify Gray Leaf Spot
Small, olive-green to gray lesions on grass blades
Lesions develop tan centers with dark brown or purple borders
Affected blades twist and wilt, giving the lawn a scorched look
Turf thins rapidly in affected areas, especially in shade
A gray, velvety coating of spores visible on lesions during humid mornings
New growth and recently mowed blades are hit first
Conditions
What Causes Gray Leaf Spot
Favorable Conditions
Daytime temperatures between 80°F and 95°F with high humidity
Extended periods of rain or overcast weather
Frequent rainfall combined with warm nights above 65°F
Excessive nitrogen fertilization during summer
Newly established turf with immature root systems
Shaded areas with poor air circulation
Susceptible Grass Types
Treatment
How to Prevent and Treat Gray Leaf Spot
Cultural Prevention
Avoid nitrogen fertilization during peak summer heat (July–August)
Water deeply and infrequently in the early morning only
Improve air circulation by pruning overhanging trees and shrubs
Mow with sharp blades — ragged cuts create entry points for the fungus
Allow new sod to fully establish before pushing growth with heavy fertilization
Professional Treatment
We apply fungicide at the first sign of gray leaf spot and adjust the fertilization schedule to reduce nitrogen during peak disease pressure. Preventive applications are recommended for St. Augustine lawns with a history of recurring gray leaf spot. Reducing leaf wetness through proper irrigation timing is just as important as chemical control.
Left untreated
What Happens Without Treatment
Gray leaf spot thins turf rapidly during extended humid weather. St. Augustine is hit hardest — severe outbreaks can strip a lawn down to stolons in a matter of weeks. The thinned turf becomes a target for weed invasion, and recovery is slow if the root system has been weakened by prolonged disease pressure.
Common questions
Frequently Asked Questions About Gray Leaf Spot
Why does gray leaf spot mostly affect St. Augustine?
St. Augustine has broader, more succulent leaf blades that hold moisture longer and provide more surface area for the fungus to attack. Its growth habit also creates a dense canopy that stays wet in humid conditions.
Does fertilizing make gray leaf spot worse?
Nitrogen fertilizer in summer pushes soft, rapid growth that the fungus attacks easily. We hold off on nitrogen during peak gray leaf spot pressure and time applications for when disease risk drops.
How do I tell gray leaf spot from drought stress?
Both cause the lawn to look scorched. With gray leaf spot, individual blades have distinct lesions with dark borders. Drought stress turns blades uniformly brown without lesions. Look closely at individual blades to tell the difference.
Will gray leaf spot kill my entire lawn?
It rarely kills the grass down to the roots, but it can thin turf severely. The stolons and root system usually survive, and the lawn recovers once conditions dry out. Fungicide treatment speeds recovery and limits the damage.
Related diseases
Other Diseases Active in the Same Season
Take action
Stop Gray Leaf Spot Before It Spreads
Every day without treatment is another day the damage gets worse. Get professional disease control backed by our expert lawn care team.
