Richard, Unfortunately I am unfamiliar with the care of warm weather grasses such as Centipede and St.Augustine. I suggest you contact your local horticulture extension service or talk to the turf expert at your local independent garden center. I will say the weed and feed products are all but useless in getting rid of established weeds. You need to get a liquid product labeled for your type of grass and the kind of weed or weeds you want to get rid of. There are also herbicides that kill mosses, but broad leaf weed killers will not do the job. I believe Bayer makes one called Bayer 2 in 1 Moss And Algae Killer that comes as a hose end sprayer. Hope this helps, Best And Happy Yardening, Nancy.