I live in central Florida with Floratam St. Augustine and the product has done a creditable job of killing the fungus. Only problem is that the fungus keeps re-occuring and you have to continually apply the product.
I realized I had brown thatch spreading hugely throughout my large backyard. I bought a bag of Ferti-Lome F-Stop and my grass is coming back. It's only been a few weeks, but I'm please.