PRIME WINDOW Dallisgrass typically rears its ugly head the most in June, July and August. Photo: Syngenta
Dallisgrass may be the most aggressive grassy weed that lawn care operators (LCOs) contend with — especially when it comes to postemergent control.
Fall is the best time to control dallisgrass, says Maggie Reiter, area environmental horticulture advisor at the University of California Cooperative Extension.
By timing applications in the fall, LCOs can target dallisgrass when it’s most sensitive to herbicides. Fall applications provide longer-lasting results and more long-term control, according to Lane Tredway, technical services manager for Syngenta.
Understand the weed
A common weed in turfgrass areas, dallisgrass has coarse leaves and a clumpy form, which make it stand out, Reiter says.
Maggie Reiter
Usually when an LCO is called in to address the weed, it’s not the best time to effectively control it, Tredway says. “It becomes big, ugly and most objectionable to customers in June, July and August,” he says.
Correct identification is important since dallisgrass competes in a lot of different environments.
“Dallisgrass is often confused with crabgrass, and misidentification can reduce the efficacy of weed control practices,” Reiter says.
Cultural control methods are limited because dallisgrass is not encouraged by soil conditions or growing conditions, Tredway says.
Prevention is the best approach, Reiter says. Maintain a healthy turf stand at an appropriate mowing height. Tredway agrees. “Healthy, dense, uniform turf is going to compete against dallisgrass and keep it from becoming established in the first place,” he says.
Controlling dallisgrass typically doesn’t happen within one or two herbicide applications. Photo: Bayer
Manage with persistency
Lane Tredway
With a consistent herbicide program, Tredway says good dallisgrass control might take more than a couple years to achieve.
“Unlike a lot of other turf weeds, you’re not going to kill or control dallisgrass with just one or two applications,” Tredway says. Strong rhizomes of the weed help it survive and regrow through multiple herbicide applications, he adds.
Apply a systemic herbicide where the weed absorbs the active ingredients. The first application should be applied in late summer or early fall. A follow-up treatment can be applied 30 days, or four to six weeks, later. If dallisgrass shows signs again in the spring, another application is required.
Tredway advises being consistent with both fall and spring applications.
“If you only do fall and skip spring, you’re going to be right back where you started or maybe even lose ground against the weed over time,” he says.
Look for products that contain the following active ingredients: pinoxaden, foramsulfuron, trifloxysulfuron, mesotrione or fluazifop.
Read more: Fact facts to defeat dallisgrass
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