How to Get Rid of Crabgrass in Bermuda Grass

Crabgrass is a clump-forming annual grass. The stem is round, which separates it from nutsedge, whose stem is triangular. Seed heads spread like fingers from one point. Smooth and large crabgrass are the two species extension pages treat together. They differ in leaf hairs. The control program is the same. It shows up in thin Bermuda, along edges, and in spots the mower scalps. It is not a sign that the lawn needs a heavy spring feeding.

It lives one season. Seed sprouts in spring, plants grow through summer, they drop seed, and frost kills the plant. The seed is what you are fighting next year. Purdue calls cultural habits, especially mowing high enough to keep a dense lawn, the most effective prevention. Herbicide is for the years the stand is not there yet.

Crabgrass seed needs light and a gap. Low mowing, thin spots after winter, traffic, and bare soil along the driveway all qualify. The germination cue is soil temperature, not a date on the calendar.

Purdue turf specialists describe germination at about 60°F for 3 to 5 days, measured near a quarter inch deep, and they want the pre-emergent down at least a week or two before that. University of Georgia's professional pest guide ties crabgrass germination to surface soil around 55°F, and it puts the pre-emergent window at February 15 to March 5 in South Georgia and March 1 to March 20 in North Georgia. Penn State describes germination when the upper inch of soil is about 55 to 58°F at daybreak for several days. Those numbers are the same story told from different states: be early, and use your soil, not Indiana's average date.

This site's soil temperature tracker flags about 50 to 55°F at roughly 2 inches as the stretch to get a pre-emergent down, which is the "ahead of germination" reading drawn from Minnesota and Penn State. On a Gulf Coast or Texas Bermuda lawn that window can open in late winter. Waiting for a Northern April date means the seed has already started. The longer version is the crabgrass pre-emergent soil temperature guide and spring timing by region.

Nothing is up yet. Apply a pre-emergent labeled for your grass before germination, and water it in if the label requires that. Prodiamine, dithiopyr, and pendimethalin are the usual active ingredients. They are not interchangeable. Dithiopyr can also affect very young crabgrass that has just emerged, up to about one tiller in Purdue's account. Prodiamine does not. The comparison is on prodiamine versus dithiopyr, and current store prices are on the pre-emergent price guide. Do not use a pre-emergent on a lawn you are about to seed. It stops the grass seed too.

Seedlings are small. This is the only honest post-emergent window. Purdue says post-emergent products work best on small plants and are hard for most homeowners to use well. Kansas State notes that quinclorac, a common active ingredient in crabgrass killers, is labeled for many cool-season and warm-season grasses, and that control depends on how many tillers the plant has. The label, not this page, says whether your Bermuda, zoysia, or other grass is on that list. St. Augustine is sensitive to a lot of herbicides, including products built around 2,4-D. If your grass is missing from the label, do not spray it.

The plants are large, tillering, and it is late summer. Purdue tells Indiana homeowners not to count on a herbicide rescue after about mid-July, because the plants are too big. A Southern lawn reaches that "too big" stage earlier in the calendar. Mow so the crabgrass does not shade the Bermuda, pull isolated plants before they drop more seed, and put the real application on the calendar for next spring's soil-temperature window. Frost will kill this year's plants. It will not kill the seed.

Goosegrass often germinates later, in warmer soil. A lawn that "got crabgrass in June" after an early pre-emergent is sometimes a different grass. The pre-emergent overview separates the spring application from the fall one aimed at Poa annua.

• Applying pre-emergent after you can see crabgrass and expecting those plants to die. Except for the early post-emergent effect of some products on tiny seedlings, pre-emergent stops germinating seed. It is not a cleanup spray.
• Using a date from a Northern article. South Georgia's window is often February. Yours moves with the soil.
• Stacking a heavy nitrogen "wake up" feeding on dormant Bermuda the same weekend as the herbicide. The pre-emergent is for the weed. Nitrogen waits until Bermuda is actually growing. See the Bermuda calendar.
• Mowing low. Short grass is an invitation.
• Spraying a crabgrass killer that is not labeled for your grass, especially on St. Augustine.
• Skipping the water-in step the label asks for, so the product stays in the thatch.