Gray Leaf Spot: Should You Be Concerned?

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grass Gray Leaf Spot is beginning to show activity on St. Augustine lawns in the south and southeastern parts of the country. This is an important infectious disease and can also occur on cool-season grasses, Tall Fescue and Perennial Ryegrass, although it generally shows up on those grasses later in the summer. This disease shows up on St. Augustine when the weather becomes hot and humid. It affects the turf by severely blighting and defoliating the leaves of the grass, but does not affect the roots. It is more of a problem on lawns that receive excessive amounts of nitrogen fertilizer during the summer months, so be careful about adding too much nitrogen to your lawn in the heat of the summer.

5 Contributing Factors:

  1. Soil compaction
  2. Improper irrigation practices
  3. Watering at night - the disease can spread rapidly when it has temperatures of 85° or higher.
  4. Humidity
  5. Time of the year: specifically, June through September


On St. Augustine, symptoms of the disease include leaf spots with reddish brown borders. The center of the spot takes on a tan color and they may grow together to form large blighted areas. It gets its name from the gray fungal growth, that resembles gray velvet, which appears on these spots during wet, humid weather.

gray leaf spot

When the spots become numerous, the entire leaf may wither and die.  The turf will take on a blighted or scorched look. Some patches will develop more of the disease than other areas of the lawn. These spots can be confused with drought stress or even insect activity.


There are disease control treatments that can be applied if the disease is caught early. Once the grass blades start to die off, it becomes much harder to help the lawn recover. One thing to remember is that the grass blades that have the disease will need to drop off. New grass blades that grow in their place will have less or none of the disease symptoms present. Sometimes customers ask about the amount of fertilizer that is applied to a lawn and ask whether it is causing the particular type of disease to occur. It is a very good question. Spring-Green’s lawn care programs are adapted to the type of turf grass that is being treated. We have worked with university consultants, product manufacturers and industry experts to put together lawn and care programs that meet the needs of the turf and provide the results that our customers desire. It is never a good idea to try to supplement our programs by adding additional fertilizer on your own. We guarantee results for our full program customers. If you are unhappy with results, contact us and we will work with you to make it right or we will refund your money for that application. Monitor your lawn for this serious disease. If you suspect your lawn has Gray Leaf Spot, contact your neighborhood lawn care professional at Spring-Green to check your lawn and they can advise you on treatment options.