Once seeds germinate and crabgrass sprouts emerge, then it’s time for post-emergent herbicides, which Target plants instead of seeds. Crabgrass killers are designed to kill existing actively growing crabgrass plants before they can produce more seed.
Unfortunately, once crabgrass has germinated and begins to grow, there are very few or no herbicides available to homeowners or commercial applicators that can kill it without harming most types of turfgrass growing in Florida.
When using crabgrass killers or any herbicides, it’s important to understand whether the product is a selective or non-selective herbicide. Selective herbicides target specific weeds or plant categories, such as grassy plants versus broadleaf plants. Non-selective herbicides kill all plant types, including lawn grasses and other plants you want to keep. Post emergence control is limited. Currently, there are no labeled post-emergent herbicides for selective control of crabgrass in St Augustine grass turf. Newly labeled herbicide triphloxisulfuron (Monument) is not labeled for use on residential turf and foramsulfuron (Revolver) although labeled for professional use on residential turf, is injurious to St Augustine grass and therefore cannot be used.