No just keep mowing, watering and fertilizing. The St. Augustine will take over, get thick and choke out the crabgrass slowly. Next spring when the crabgrass seeds try to sprout a thick St. Augustine will choke them out. You can put down a preemergence weed killer in spring if you like but it may not be needed if your lawn is thick at that time. Your County Extension Office can assist by providing the best timing for a preemergence weed killer.
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