I use Expert St. Augustine weed and feed, and it does a great job. It’s by Expert and it’s just for St. Augustine grass, it will state on the bag, St. Augustine. After the St. Augustine weed and feed is down for about two months, I use the following mixture.
Lawn Care Recipe (mix all items and put into a sprayer connected to hose)
One full can of regular Cola pop (any kind-no diet soda)
One full can of beer (no light beer)
1/2 Cup of Liquid dishwashing soap (do NOT use anti-bacterial dishwashing liquid)
1/2 Cup of household ammonia