The secret to using cooling degree days to control dallisgrass this fall

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

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 (CDD) email alerts on GreenCastOnline.comResearch at the University of Tennessee has shown CDDs 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:

Monument® 75WG and Manuscript® herbicides are labeled for dallisgrass control in bermudagrass and zoysiagrass turf: 
  • Monument 75WG may be applied as a broadcast application or spot treatment at 15 g/A
    • Include a non-ionic surfactant at 0.25% v/v or 0.32 fl. oz./gal. of water
    • A second application four to six weeks later is recommended in most cases
    • Monument 75WG also provides broad-spectrum control of many broadleaves, grasses and sedges
  • Manuscript is most effective when applied as a spot treatment using 0.96 fl. oz. Manuscript and 0.64 fl. oz. Adigor™ surfactant in 1 gal. of water to treat 1,000 ft.2 
    • Make a second application 14 to 21 days later and treat no more than 10,000 ft.per year
    • In addition to dallisgrass, Manuscript effectively controls crabgrasses and several other grassy weeds
Recognition® herbicide + Fusilade® II turf and ornamental herbicide can be applied as a tank mixture for dallisgrass control with excellent safety to St. Augustinegrass and zoysiagrass turf. 
  • The proprietary safener in Recognition, metcamifen, safens Fusilade II in St. Augustinegrass and zoysiagrass without impacting dallisgrass control
  • The recommended rates are Recognition at 1.29 oz./A and Fusilade II at 24 fl. oz./A
  • Include a non-ionic surfactant at 0.25% v/v or 0.32 fl. oz./gal. of water 
  • If needed make a second application four to six weeks later when dallisgrass regrowth is observed

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.
Fusilade II applied alone at 3-6 fl. oz./A is an option for dallisgrass control in tall fescue turf, including residential lawns. Include a non-ionic surfactant at 0.25% v/v or 0.32 fl. oz./gal. of water. Make a repeat application 30 days later, but avoid spray overlaps or application on turfgrasses under stress, which may induce unacceptable turf injury. Note that Fusilade II will severely injure other cool-season grasses like Kentucky bluegrass or perennial ryegrass so it should only be applied to pure stands of tall fescue. 

Product(s)Tolerant Turf SpeciesRecommened Rate(s)Recommended SurfactantApplication Method
Monument 75WGbermudagrass, zoysiagrass15 g/ANIS 0.32 fl. oz./gal. of waterbroadcast or spot treatment
Manuscriptbermudagrass, zoysiagrass0.96 fl. oz./1,000 ft.2Adigor 0.64 fl. oz./gal. of waterspot treatment only; treat no more than 10,000 ft.2/A
Recognition + Fusilade IISt. Augustinegrass, zoysiagrass1.29 oz. + 24 fl. oz./ANIS 0.32 fl. oz./gal. of waterbroadcast or spot treatment
Fusilade IItall fescue3-6 fl. oz./ANIS 0.32 fl. oz./gal. of waterbroadcast or spot treatment

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.

For more information contact your local Syngenta territory manager

Always consult the product label for complete use and application information

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

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

© 2023 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. Syngenta supports a FIFRA Section 2(ee) recommendation for tank mixing Recognition and Fusilade II to remove bermudagrass from zoysiagrass and St. Augustinegrass. Please see the Section 2(ee) recommendation to confirm that the recommendation is applicable in your state. The Section 2(ee) recommendation for tank mixtures with Recognition should be in the possession of the user at the time of application. Adigor™, Fusilade®, GreenCast®, Manuscript®, Monument®, Recognition® and the Syngenta logo are trademarks of a Syngenta Group Company. All other trademarks are property of their respective third-party owners.

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