Question: I’m getting tons of questions from anxious gardeners whose St. Augustine lawns appear to be dying, one quickly browned area after another. It’s a very common issue with lawns every fall. I have the answer for you.Answer: Brown patch is a cool-season fungal leaf disease that attacks St. Augustine from late September through November. It was a bit later this year due to the dry times of early fall.
Brown patch first appears as yellowed patches 18 to 24 inches in diameter. Within days, the blades within those patches turn entirely brown. When you pull on affected blades, they will come loose from the runners without resistance. You’ll see where they are decaying if you look closely at the ends where the blades attach to the runners.
The fungus is spread by moisture. Do not irrigate in the evening (only in early mornings). Apply a labeled turf fungicide from your favorite nursery or hardware store at first signs of the disease.
While brown patch won’t kill the grass on its own, it weakens it enough that a bad winter could do unnecessary harm to the affected grass. By spring, all the grass will green back up uniformly. So if you have brown patch in your St. Augustine, you can at least begin to breathe once again. It isn’t as bad as you probably thought.