Using cooling degree days to control dallisgrass this fall

 dallisgrass untreated plot
Dallisgrass untreated; Source: Syngenta, 2018.
By Lane Tredway, Ph.D., technical services manager, Syngenta

Dallisgrass is an aggressively growing, perennial weed that becomes particularly objectionable in mid-summer around July and August. Traditionally, this is not the best time to control dallisgrass with herbicides. Herbicides are most effective against dallisgrass in late-summer and fall, when more downward translocation is occurring as the plant prepares for winter dormancy.

To assist with proper timing of fall applications, you can sign up for Cooling Degree Day email alerts on greencastonline.comResearch at the University of Tennessee showed that Cooling Degree Days (CDD) are useful for timing late summer and fall applications to target dallisgrass. Applications were most effective when applied between 10 and 225 CDD72F. CDDs are the opposite of Growing Degree Days as they track the accumulation of cool temperatures as the year progresses.

Syngenta offers three products for dallisgrass control, which are effective components for a dallisgrass program:
Manuscript® herbicide is labeled for use in bermudagrass and zoysiagrass turf and in St. Augustinegrass sod. For dallisgrass control, apply Manuscript as a spot-treatment using 0.96 fl. oz. Manuscript and 0.64 fl. oz. Adigor™ surfactant in one gallon of water to treat 1000 ft.2. Make a second application 14 to 21 days later and treat no more than 10,000 ft.2 per acre per year. In addition to dallisgrass, Manuscript effectively controls crabgrasses and several other grassy weeds.

To combat turfgrass insects, weeds and diseases such as crabgrass, sign up to receive Soil Temperature Alerts when soil temperatures hit target thresholds in your area.
Monument® 75WG herbicide is effective for dallisgrass control in bermudagrass and zoysiagrass turf. Monument may be applied as a broadcast application at 15 grams per acre. A second application four to six weeks later is recommended in most cases. Monument also provides broad-spectrum control of many broadleaves, grasses and sedges.

Fusilade® II turf and ornamental herbicide is labeled for use in tall fescue and zoysiagrass turf, including residential lawns, at 3 to 6 fl. oz. per acre as specified on the product label. Make a repeat application 30 days later, but avoid spray overlaps or application on turfgrasses under stress, which may induce unacceptable turf injury. These applications will also suppress or control bermudagrass contamination in tall fescue landscapes.

Additional applications in spring to early summer are also recommended to keep the dallisgrass from rebounding. Managing dallisgrass is a long-term endeavor, likely requiring fall and spring applications over several years to control well-established plants. Cultural practices to improve turf density and competitiveness can also improve the efficacy of dallisgrass programs.

Syngenta hereby disclaims any liability for Third Party websites referenced herein.

All photos are either the property of Syngenta or are used with permission.

© 2021 Syngenta. Important: Always read and follow label instructions. Some products may not be registered for sale or use in all states or counties and/or may have state-specific use requirements. Please check with your local extension service to ensure registration and proper use. Adigor,, Fusilade®, Manuscript®, Monument® and the Syngenta logo are trademarks of a Syngenta Group Company.

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