I apologize for this delayed reply to your gardening question and hope it is still helpful to you. Unfortunately there is not a product that will kill centipede or bermuda but not St. Augustine. If you fertilize in spring summer and fall the Centipede will be at a disadvantage over the other grasses and will likely slowly decline. I think the only option for removing the bermuda is spraying it and trying to direct sprays to it as much as possible and the St. Augustine as little as possible. When the bermuda dies after about a week or so then set out the St. Augustine. If you can tolerate some dead spots for a while it would be better to wait a month or more since you won't get all the bermuda with one spray and then you can retreat once or twice to be more sure of good control before planting the new St. Augustine in.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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