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Gray Leaf Spot

Q:  What is wrong with my St. Augustinegrass? 

Q:  What is wrong with my St. Augustinegrass?  It seems to be dying in large areas all around my yard.

A:   I have received dozens of phone calls and office visits regarding this very question within the last two weeks. Because of all the rain we have been receiving, it would be best if we all placed our irrigation systems on manual. I have not needed to run my irrigation system in almost two months. I realize we are allowed to run our irrigation twice a week according to St. Johns River Water Management but it does not mean we must or should. Please look at the blades of grass and if they are flat and dark green then it is not necessary to run your irrigation. When the blades begin to slightly fold onto themselves, then it is time to irrigate.

Part of the diagnosis process is examining the lawn grass. It was essential for you to submit a sample to me (12 inch by 12 inch) which includes the roots, stolon, blades and soil.  After looking at your sample it was easy to determine one of the problems was grey leaf spot. If left untreated, it can destroy the lawn but your specimen also show root rot and decline. Once the roots of any plant are destroyed, it is nearly impossible for the plant to recover.  In addition, we have no chemical able to correct this type of root damage to lawn grass.

Our best method of control is prevention.  How do we prevent this problem in the future?  We must control the amount of water applied to the lawn. St. Augustinegrass prefers to be watered deeply but less often than we would assume. The root rot caused the blades to wilt. This reaction often makes us assume the grass needs more water so we turn on the sprinklers only to be causing the disease to spread even farther. What can you do now?  Rake out any dead grass, reduce the amount of water used, do not apply high nitrogen in the summer and avoid using weed killers in the high temperatures.