Question of the Week Number 1: July 26, 2018
“What is wrong with my St. Augustine? I’ve added iron and nitrogen. Nothing seems to help.”
This is gray leaf spot. We’ve talked about it before here this summer. (See July 5 issue) However, it’s come up so many times it merits repeating.
This is a fungal disease that attacks St. Augustine during the hottest part of the summer. I describe it as creating “washes” of yellowed grass, as you can see in Scott H’s photo above.
However, to confirm its presence you have to look more closely at the affected areas, and that’s when you’ll see the diamond-shaped spots on the blades and occasionally on the runners as well.
How to deal with gray leaf spot…
• First and foremost, withhold all nitrogen fertilizer from your lawn during the summer. Nitrogen exacerbates this disease. Do not fertilize St. Augustine between mid-June and early September. It may be that gray leaf spot was unusually bad this year because of the early arrival of really high temperatures in June.
• Apply a labeled turf fungicide to stop the current outbreak. Your local independent retail garden center will show you the products available for its control. However, I learned when this disease broke out in my own yard in the mid-1990s that avoiding nitrogen was far more effective than trying to treat with fungicides. I just spent 30 minutes online on various university plant pathology websites, and they repeated that suggestion several times over.