By Lane Tredway, Ph.D., technical services manager for Syngenta

Zoysiagrass has many desirable properties that make it an ideal turfgrass for transition zone climates. As a warm-season grass, it:

• Is able to withstand severe heat and drought
• Has excellent wear tolerance
• Has good tolerance to shade and cold temperatures
• Requires less fertilization or other inputs

In recent years, turfgrass breeders have developed zoysiagrass varieties that thrive in a variety of settings, from low-maintenance areas to intensely managed golf course putting greens. However, the inability to control bermudagrass infestations in zoysiagrass turf has been a major challenge for turfgrass managers. Certain products like Turflon^® Ester Ultra specialty herbicide, Acclaim^® Extra herbicide or low rates of Fusilade^® II herbicide suppress bermudagrass temporarily, but can also injure zoysiagrass if applied too frequently or during periods of stress. A solution for bermudagrass control has remained elusive — until now.

Recognition^® herbicide is a recent Syngenta herbicide formulation that contains trifloxysulfuron, the active ingredient in Monument^® 75WG herbicide, with a proprietary herbicide safener called metcamifen. Recognition makes it possible to control bermudagrass with excellent safety to zoysiagrass. 

Recognition alone does not control bermudagrass, but when tank mixed with Fusilade II at rates up to 24 fl. oz./A, the combination controls bermudagrass without injuring zoysiagrass. How is this possible? The safener in Recognition, metcamifen, triggers certain grass species to tolerate certain herbicides, like Fusilade II, without impacting its activity on weed species like bermudagrass.

The Recognition 2(ee) label allows for a tank mix of Recognition + Fusilade II to control bermudagrass out of established zoysiagrass turf:

• Apply Recognition (1.29 oz./A) with Fusilade II at 24 fl. oz./A
  • While 12-24 fl. oz./A of Fusilade II can be used, we recommend 24 fl. oz./A for greatest efficacy
• Include a non-ionic surfactant at 0.25% v/v or 0.32 fl. oz./gal. of spray solution
• Use typical spray volumes from 20-80 gal. of water/A
• Use flat-fan nozzles that produce medium-to-coarse droplets to ensure uniform foliar coverage
• Provide adequate fertility and irrigation to encourage zoysiagrass growth and spread
  • Avoid overfertilization, as most zoysiagrass varieties only require 2-3 lb. N/1,000 ft.² per year

Depending on the amount of bermudagrass present and how well-established it is, additional applications of Recognition + Fusilade II may be necessary to maintain bermudagrass control until the zoysiagrass can spread into the voids left behind. Application intervals vary by time of year and growing conditions, but typically are four weeks for 12-18 fl. oz./A of Fusilade II or five to six weeks for 24 fl. oz./A of Fusilade II. The active ingredient in Fusilade II is foliarly absorbed, so it is best to apply once the bermudagrass begins to regrow in treated areas.

The below images depict Meyer zoysiagrass with bermudagrass sod planted in the center of the plots. The untreated control (left) shows no injury to either species. However, two applications on a 30-day interval of a tank mix of Recognition + Fusilade demonstrate turf safety to the zoysiagrass and control of the bermudagrass.

Untreated control	Recognition + Fusilade II at 1.29 oz./A and 24 fl. oz./A

Source: Daniel Earlywine, PARC Research and Consulting, 2023. Photos taken on Sept. 26, 2023, 14 days after the second application. Treatments of Recognition + Fusilade II at 1.29 oz./A and 24 fl. oz./A mixed with Chem-Stik non-ionic surfactant at 0.25% v/v.

Since Recognition contains trifloxysulfuron, applications targeting bermudagrass will also control many other weeds, including:

• Sedges
• Kyllingas
• Many broadleaves
• Poa annua

The 24 fl. oz./A rate of Fusilade II also provides excellent control of goosegrass and dallisgrass.

Caution should be exercised when applying Recognition around desirable cool-season grasses since trifloxysulfuron can move with runoff water, equipment and foot traffic. To minimize potential movement onto sensitive turf species:

• Lightly irrigate approximately three hours after applying Recognition to reduce foliar residues
• Run additional irrigation cycles the following two mornings to remove dew
• Leave an untreated buffer at least 10 ft. wide around golf course putting greens
• Avoid applying Recognition to slopes above creeping bentgrass putting greens or to severe slopes around other cool-season grasses

For more information about Recognition, visit GreenCastOnline.com/Recognition.