I have St. Augustine grass in my backyard. It is a lovely, but tricky grass to keep healthy. Cass (Carter Wee and Pest Control) has this same grass at his home. We tried a sample weed killer that proved effective and then a week later I had him spray the whole yard. In less than 2 weeks, I now have a weed free lovely lawn. It is all in knowing the right product and Carter Weed and Pest found the right one for me.