Do you get sub-freezing temperatures down there? If so, it will be gone after the first frost and won't return until the weather gets fairly hot next spring. The best way to control crabgrass is to mow your lawn a little higher and water less often but more deeply. The herbicide most often used as a pre-emergent against crabgrass is Pendimethain. One of the more common brand names is Scott's Halts Crabgrass Preventer.
