Jonathan from Clearwater, Florida writes
QuinKill Max Crabgrass and Weed Killer cannot be used on St Augustine grass, Bahiagrass, carpetgrass or dichondra. Unfortunately there really isn't a post-emergent crabgrass killer that can be used on St Augustine grasses available unless you are willing to go to a higher price point. We do carry Echelon 4SC and it is labeled for use on St Augustine. Still the product label does warn "Application of Echelon 4SC to St. Augustinegrass may cause temporary discoloration to exposed leaf surfaces of St. Augustinegrass. Treated turfgrass will
recover with new growth and discolored leaf tissue will be removed with mowing."
Answer last updated on: 01/16/2013