Topramezone is a promising new herbicide for bermudagrass control in cool-season turf.  It is similar to mesotrione (Tenacity®) in that it controls many grassy and broadleaf weeds and is safe to many cool-season turfgrasses.  Topramezone can effectively control crabgrass, goosegrass, and white clover with a single application and is more effective than mesotrione for bermudagrass control.  Topramezone should be marketed in the coming year, but its trade name is unknown at this time.  The objective of this study was to determine if topramezone alone or in combination with triclopyr (Turflon® Ester) or quinclorac (Drive XLR8®) is effective in controlling bermudagrass in cool-season turfgrasses, and how these treatments compare to the industry standard of fenoxaprop (Acclaim® Extra) plus triclopyr (Turflon® Ester).

A study was initiated on July 20, 2012 on a ‘Kelly’ Kentucky bluegrass lawn maintained at 7.6 cm at the Turfgrass Research Center (TRC) of Virginia Tech in Blacksburg, and infested with approximately 70-80% bermudagrass.  Treatments consisted of topramezone applied alone, with triclopyr, or with quinclorac and compared to fenoxaprop + triclopyr and mesotrione + triclopyr.  All treatments were applied three times.  Rates of topramezone were 0.04 kg ai ha^-1 for the first two applications and 0.02 kg ai ha^-1 for the third application.  Rates of triclopyr, quinclorac, fenoxaprop, and mesotrione were 1.12, 0.42, 0.10, and 0.21 kg ai ha^-1, respectively.  All sequential treatments were applied at three-week intervals.  All topramezone treatments included a methylated seed oil surfactant (0.5% v/v).  An untreated check was included for comparison. 

Topramezone + triclopyr controlled bermudagrass 94% and significantly better than topramezone + quinclorac, fenoxaprop + triclopyr, and mesotrione + triclopyr, which only controlled bermudagrass less than 71%, 57 days after initial treatment (DAIT).  Topramezone applied alone controlled bermudagrass 85%, 57 DAIT, but not significantly different from topramezone + triclopyr, topramezone + quinclorac, or mesotrione + triclopyr.  For the three treatments that contained triclopyr, white leaf tissue (mostly weedy bermudagrass) comprised less than 5% of plot area.  Topramezone alone and topramezone + quinclorac had over 30% white leaf tissue in plots.  Kentucky bluegrass was not injured at any timing in this study.