Evaluation of Herbicides and their Tank‐Mixes for Suppression of Bermudagrass in Zoysiagrass

Abstract

Zoysiagrass (Zoysia spp.) is a popular turfgrass species for use on lawns, sod farms, and golf courses in the transitional and southern climatic zones of the United States. One common problem in managing zoysiagrass is the contamination and subsequent removal of bermudagrass (Cynodon spp.). Various herbicides and herbicide tank‐mixes may be utilized for bermudagrass control in zoysiagrass. Research was conducted in Fayetteville, AR, and Auburn, AL, to evaluate aminocyclopyrachlor, fluazifop, fenoxaprop, triclopyr, and their combinations for bermudagrass suppression in zoysiagrass. Fluazifop at 0.105 kg active ingredient (a.i.) ha–1 suppressed bermudagrass most, but this application caused unacceptable injury and quality reduction to zoysiagrass. Tank‐mixing fluazifop or fenoxaprop at 0.14 kg ai ha–1 with triclopyr at 0.56 kg acid equivalent (a.e.) ha–1 reduced zoysiagrass injury and improved turf quality over fluazifop or fenoxaprop alone. Fluazifop + triclopyr provided more bermudagrass suppression than fenoxaprop + triclopyr. Aminocyclopyrachlor (0.026 or 0.071 kg a.e. ha–1) did not reduce herbicide injury from fluazifop or fenoxaprop applications to zoysiagrass and did not provide significant bermudagrass suppression. Results suggest that fluazifop + triclopyr and fenoxaprop + triclopyr remain the best treatments for bermudagrass suppression in zoysiagrass because they provide bermudagrass suppression without reducing zoysiagrass quality.

Application Timing Affects Tolerance of Zoysiagrass to Fluazifop‐P‐butyl and Safening Effect of Triclopyr

“…A similar pattern was observed for the highest rate of fluazifop‐P‐butyl in summer and fall. Overall, Geo zoysiagrass maintained acceptable quality (i.e., ≥6) when triclopyr was included in the tank mixture, which agrees with previous studies with Cavalier, Meyer, and ‘Zorro’ zoysiagrass where triclopyr consistently maintained turf treated with fluazifop‐P‐butyl at acceptable levels (Patton et al, 2017b).…”

“…This is because greater control can be achieved after a single application by targeting the most susceptible growth stage of that weed population, such as targeting bermudagrass growth stage with 10-to 20-cm stolon for fluazifop-P-butyl application, as specified by the label. This reduced frequency of application could also translate to financial savings (Patton et al, 2017b). Previous studies have reported that triclopyr used alone on Emerald, Zorro, Cavalier, and Meyer zoysiagrass consistently led to <1% visual injury 6 WAT, which remains the case in our study for Zeon zoysiagrass but not for Empire or Geo zoysiagrass (Flessner et al, 2011a;Lewis et al, 2010;Patton et al, 2017b).…”

“…This is because greater control can be achieved after a single application by targeting the most susceptible growth stage of that weed population, such as targeting bermudagrass growth stage with 10‐ to 20‐cm stolon for fluazifop‐P‐butyl application, as specified by the label. This reduced frequency of application could also translate to financial savings (Patton et al, 2017b).…”

“…This reduced frequency of application could also translate to financial savings (Patton et al, 2017b). Previous studies have reported that triclopyr used alone on Emerald, Zorro, Cavalier, and Meyer zoysiagrass consistently led to <1% visual injury 6 WAT, which remains the case in our study for Zeon zoysiagrass but not for Empire or Geo zoysiagrass (Flessner et al, 2011a;Lewis et al, 2010;Patton et al, 2017b). However, despite being commonly identified as a broadleaf weed-targeting herbicide, injury related to triclopyr has also been reported in other warm-season grasses including St. Augustinegrass and bermudagrass (Bell et al, 2000;Alligare, 2008;Lewis et al, 2009Lewis et al, , 2010Doroh et al, 2010).…”

Variation in tolerance mechanisms to fluazifop-P-butyl among selected zoysiagrass lines

“…Fluazifop-P-butyl can be used for grass weed control in zoysiagrass establishment. However, the rate necessary to ensure weed control and zoysiagrass safety is largely dependent on the cultivar (Leon et al 2014;McElroy and Breeden 2006;Patton et al 2017b). Based on our results, fluazifop-P-butyl tolerance could be composed of multiple non-target site (NTS) mechanisms likely controlled by multiple genes that vary among different Zoysia genotypes, and as a result of this, conventional breeding approaches for creating more fluazifop-P-butyl-tolerant zoysiagrass lines will be challenging.…”