I write about this topic each year because with St. Augustinegrass you basically have one shot to control crabgrass. With what seems like an early spring to this point, there may not be much time before crabgrass begins to emerge.

There are no selective herbicides that will provide good or excellent control of crabgrass in St. Augustinegrass once it has germinated. St. Augustinegrass has fewer post-emergence options for weed control than other warm season turfgrasses. Postemergence means “after the weed has germinated.” There are, however, several pre-emergence herbicides that will control crabgrass. Pre-emergence means “before they germinate.”

The key to using a pre-emergence herbicide is to apply it before grass weeds germinate. Once crabgrass emerges in St. Augustinegrass, successful control with post-emergence herbicides is fair at best. The time to apply pre-emergence herbicides in southern and coastal Georgia is late January to early March.

One of the old standby herbicides for many broad-leaf weeds, Atrazine, has limited success on crabgrass. It has fair pre-emergence activity and will provide fair control to newly emerged crabgrass. Fair control means that it provides 70-79% control if applied properly. If crabgrass is not your main weed, atrazine may be all you need.

If crabgrass is your main weed, you need to target crabgrass with a pre-emergence herbicide. Fortunately, there are several options. Balan, which contains benefin, Green Light Amaze and XL, which contain benefin + oryzalin, and Halts, which contains pendamethalin, are all listed as providing excellent pre-emergence control of crabgrass.

Hi-Yield Crabgrass Preventer, and Team, both of which contain benefin + trifluralin, and Surflan, which contains oryzalin, are also excellent for pre-emergence control. Excellent means they control 90-100% of weeds if applied correctly.

When you purchase one of these products, make sure you read the label carefully. For instance, products containing pendamethalin may state things like, “Do not use on severely thinned turfgrass” or “Do not use on newly seeded or sodded areas until after the fourth mowing.”

Products containing benefin, oryzalin, or both may state things like “Do not make a spring application to fall planted turfgrass” or “Use only on healthy established turfgrass.” Make sure you pay attention to these labels.

All of the above herbicides can also be used on St. Augustinegrass, as well as zoysiagrass, centipedegrass and bermudagrass. Atrazine should only be used on dormant bermudagrass.

Unlike St. Augustinegrass, in centipedegrass products containing sethoxydim (Vantage) can be used to kill emerged crabgrass. Sethoxydim also suppressed bahiagrass and bermudagrass so it is a good herbicide to own if you have a centipedegrass lawn.

In zoysiagrass and bermudagrass, products containing quinclorac (Drive) will control crabgrass. Weed control can get complicated because there are so many herbicide options out there and so many grasses and restrictions with each product. Make sure you read the label carefully and make sure the product can be used on your turfgrass. Growing a healthy, thick turfgrass will shade out many weeds and prevent herbicide applications.

Jake Price is a University of Georgia extension agent/coordinator in Lowndes County. More information: Call (229) 333-5185 or email jprice@uga.edu.