Question of the Week – Number 2: December 16, 2021
“What is causing my lawn to look this way? Someone told me it was brown patch, but fungicides haven’t helped. What can I do?”
Indeed, your photo does show brown patch (now being referred to as “large patch” by some Texas A&M specialists). I’ve been asked this same question several times in the past week. You can always confirm brown patch by pulling on the leaf blades gently. If brown patch is involved they will come loose very easily and you’ll be able to see the rotted areas where they once attached to the runners.
At this late date the grass may be too dried to separate quite so easily, but you should still be able to see where the fungus attacked the blades.
The fungicide azoxystrobin will control brown patch as well as take all root rot and gray leaf spot, the other common and serious St. Augustine diseases of spring and summer respectively. However, you’ll want to apply it early in the brown patch season, not in December.
At this late date there is probably little reason to treat. Try to get ahead of the infection earlier next fall. Watch for the first evidence of circular patches of grass to start turning yellow following the first cool (60F), rainy spell.