I found these steps on the internet to how you can kill crab grass and keep it from returning. Best of luck! 🌸
I use Spectracide Weed and Feed in the hose end spray bottle. No mixing no mess. Kills the weeds and feeds the lawn. A thicker lawn leaves no room for weeds.
In Florida I use Baking Soda. I just sprinkle it on the crabgrass. The Baking Soda does not affect the St Augustine grass.
crabgrass will naturally die in the winter but it leaves a lot of seeds behind. In the fall aerate and overseed and then apply pre-emergent selective herbicide early spring before the seeds can germinate. This is not an easy fix especially if there is a lot of crabgrass , but will fill in with grass over time.
If it is not in your lawn then you can use vinegar.
There is a good list of FAQs regarding crabgrass in the second half of this article: https://www.gardenlifepro.com/best-crabgrass-killer/ that I found useful.
I was unsure what crabgrass looked like and also what to do with it here in Florida.