As lawn care operators (LCOs) gear up to fight weeds in the new year, they must plan their products and applications to have the best results — especially for weeds like dallisgrass. Not only is dallisgrass difficult to control, but it also requires unique application timings to keep it from becoming an eyesore throughout the year.

Properly identify

An aggressive warm-season perennial weed, dallisgrass has a coarse texture and dull, grayish-green color, says Chris Butcher, Quali-Pro Southeast area manager. Its leaf blades are smooth and grow in clumps, and the seed heads have hairy spikelets in four rows.

Dallisgrass is commonly confused with other grassy weeds like crabgrass. However, it has a prominent mid-rib and is a taller, upright weed compared to crabgrass, Butcher says. Its seed heads are also much larger than those on crabgrass, and dallisgrass seeds are darker in color versus the white color of crabgrass seeds. Proper identification is important because the chemical products for crabgrass management won’t control dallisgrass.

Maintaining healthy turf through cultural practices — like ensuring the proper fertilization, irrigation, mowing height and using quality, weed-free seeds — helps prevent dallisgrass from becoming competitive, Butcher says. Spot spraying with non-selective herbicides or hand pulling to remove the root and underground stems (rhizomes) are other management options.

“It’s a very difficult weed to control. If they go unchecked, they can grow 3 to 4 feet and keep producing rhizomes and seeds for the following year,” Butcher says. “Keeping it mowed and the seed heads from making new seedlings is half of the battle.”

Timing is everything

Like with managing other weeds, operators want to achieve dense, healthy turfgrass through proper maintenance to keep dallisgrass at bay, says Lane Tredway, Ph.D., technical services manager for Syngenta.

Controlling diseases like spring dead spot during the spring also can help prevent dallisgrass. However, most direct treatments for this weed should come later in the year.

“The application timing for dallisgrass is unique in that with most weeds, you want to control them early in the season before they get big,” Tredway says. “But fall applications when it is beginning to prepare for winter dormancy are much more effective with dallisgrass — even though dallisgrass is more evident during the summer.”

Operators can follow the two fall postemergent applications with one or two more in the spring once the turf begins to green up. In warm-season turfgrasses, apply a postemergent with the active ingredients trifloxysulfuron-sodium or pinoxaden. In cool-season turfgrasses and zoysiagrass, postemergent products containing fluazifop work best.

Fill the void

Named for farmer T.A. Dallis who introduced the weed to the U.S., dallisgrass can dominate the landscape due to its ability to spread and produce new plants, says Jesse Benelli, Ph.D., green solutions team specialist for Envu.

Using a postemergent herbicide at the high-level rate, LCOs should spot treat to ensure they thoroughly wet the leaves with the application — but not so much that there’s runoff. They can follow the initial fall application with another one four to six weeks later — and again in the spring if there’s regrowth.

“This is one of those weeds where application timing is equally important to the product you’re using to control it. LCOs might be eager to control weeds in the spring, but it’s more effective in the fall,” Benelli says. “You can use the best chemistries available, but if you apply them at the incorrect time, you’ll get inconsistent control at best.”

Effectively managing dallisgrass is only part of the battle: Operators also need a plan in place to fill bare spots left once they control the weed.

“You need to recover desirable turf to fill those voids, or they will likely house a new set of weeds,” Benelli says.