Evaluation of New Aryloxyphenoxypropionate Herbicides for Control of Bermudagrass in Zoysiagrass

Field experiments were conducted in Auburn, AL in 2008 and 2009 to assess new aryloxyphenoxypropionate (AOPP) herbicides applied alone and tank-mixed with triclopyr for Tifway bermudagrass control in Zorro zoysiagrass. Treatments included three sequential applications of clodinafop (0.07 kg ai ha(-1)); triclopyr (1.12 kg ae clodinafop + triclopyr (0.07 + 1.12 kg ha(-1)); fenoxaprop (0.10 kg ai ha(-1)); fenoxaprop + triclopyr (0.10 + 1.12 kg ha(-1)); metamifop (0.40 kg ai ha(-1)); and metamifop + triclopyr (0.40 + 1.12 kg ha(-1)). Clodinafop, fenoxaprop, and metamifop applied alone controlled Tifway bermudagrass 32 to 65% when rated 3 wk after the final application; however, the addition of triclopyr to these AOPP herbicides increased bermudagrass control to >= 89%. All AOPP herbicides applied alone caused unacceptable injury to Zorro zoysiagrass (20 to 42%) 3 wk after the final application. Clodinafop resulted in the greatest zoysiagrass injury (42%), whereas metamifop caused moderate injury (20%). Zorro zoysiagrass exhibited less injury (< 3%) and greater turf coverage >= 95%) when AOPP herbicides were tank-mixed with triclopyr. Of the three AOPP herbicides evaluated in this study, only fenoxaprop is currently labeled for use on turfgrass. However, the nonlabeled herbicides (clodinafop and metamifop) provided bermudagrass control and zoysiagrass safety equal to the commercial standard (fenoxaprop) 3 wk after the final application when tank-mixed with triclopyr. Where zoysiagrass is contaminated with bermudagrass, turf managers will likely have to make applications of AOPP herbicides tank-mixed with triclopyr over multiple years to control bermudagrass as it will continue to regrow from deep rhizomes.