Selective postemergence herbicide control of bermudagrass in zoysia fairways

By |  November 24, 2014 0 Comments

Bermudagrass (Cynodon spp.) and zoysiagrass (Zoysia spp.) are commonly used on golf course fairways in the warm season and transition zones (Shaver et al., 2006). In Missouri and neighboring states located at the northern transition zone, common bermudagrass (C. dactylon (L.) Pers.) cultivars such as Westwood, Quickstand and U3 were once popular grasses for fairways (Dunn et al., 2001). However, because of repeated winterkill in the 1990s, a majority of Missouri golf courses renovated fairways from common bermudagrass to Meyer zoysiagrass (Z. japonica Steud.) (Foy, 2001).

Despite the renovation efforts, many superintendents in this region report the encroachment of common bermudagrass, with its characteristics of coarse leaves, thick and long stolons, and an aggressive growth habit. A bermudagrass/zoysiagrass mixture on a fairway often results in reduced turf quality and playability because of incompatible color, texture and growth rate of the two species (Fig. 1).

Bermudagrass is a difficult weed to control. For non-selective control it typically requires three sequential applications of glyphosate to obtain satisfactory (>95 percent) bermudagrass control (Teuton et al., 2005). Alternatively, previous research reported that aryloxyphenoxypropionate (AOPP) herbicides such as Acclaim Extra (fenoxaprop) and Fusilade II (fluazifop) are promising for selective control of bermudagrass in various warm- and cool-season grasses (Johnson et al., 1992). When tank-mixed with Turflon Ester (triclopyr), AOPP herbicides cause more injury to bermudagrass than to zoysiagrass, and up to 76 percent suppression of bermudagrass (McElroy and Breeden, 2006).

Tenacity (mesotrione) is an alternative tank-mix partner with AOPP herbicides for selective removal of bermudagrass. Willis et al. (2006) reported that Tenacity reduced bermudagrass cover by 45 percent to 98 percent when applied alone or tank-mixed with AOPP herbicides. Although the label indicates potential phytotoxicity to zoysiagrass, Huckabay (2008) reported three sequential applications of Tenacity up to 4 fl. oz. /A resulted in just a maximum of 15 percent injury to Meyer zoysiagrass. To date, there are no studies evaluating tank mixtures of Acclaim Extra and Fusilade II with Tenacity on golf course fairways to determine long-term control of bermudagrass in zoysiagrass turf.

Materials and methods

Field plots were established on the ninth fairway of The Falls GC in O’Fallon, Mo. The fairway was established with Westwood bermudagrass in 1994 and renovated to Meyer zoysiagrass by sod in 2009, following three sequential applications of Roundup Pro (glyphosate) at 4 qt. /A applied four weeks apart.

Shortly after sodding, bermudagrass began invading fairways and becoming interwoven with zoysiagrass (Fig. 1). The fairway soil was a Keswick silt loam with a pH of 6.7 and 4.5 percent organic matter. The fairway was maintained at a 0.56 inch mowing height and received 3.0 lbs. nitrogen /1000 ft2 fertilizer annually. Field plots measured 5 by 10 ft. and were established on two locations of the same fairway and arranged as a randomized complete block design with four replications for one location and three replications at the second location because of space limitations. Locations were fairly uniform with the possible exception of one area that had heavy golf cart traffic.

Along with an untreated control, treatments included Acclaim Extra or Fusilade II tank-mixed with Turflon Ester or Tenacity and applied to the same plots over two years (Table 1). The initial application was made on June 9, 2010, with applications made three, six, eight and 10 weeks after initial treatment in the first growing season, and 52, 56 and 60 weeks after initial treatment during the second growing season. Treatments were tank mixed with a non-ionic surfactant at 0.25 percent v/v, and applied with a backpack sprayer.

Zoysiagrass injury was rated on a 0- to 100-percent scale with 0 being no injury and 100 percent meaning complete death. Bermudagrass coverage also was rated on a 0- to 100-percent scale, with 0 percent meaning no bermudagrass and 100 percent meaning complete bermudagrass coverage. Results were statistically analyzed and mean separation was conducted based on Fisher’s Protected LSD (P = 0.05). Percent bermudagrass coverage data were arcsine transformed prior to analysis. For clarity, non-transformed means were presented, as there were no differences in interpretations.

Results and discussion

Zoysiagrass injury data are presented separately for high traffic area (HTA; Fig. 2A) and low traffic area (LTA; Fig. 2B). Treatments containing Acclaim Extra or Fusilade II and Turflon Ester resulted in 5 percent or less injury to zoysiagrass at both locations, regardless of the rates applied. These results agree with Lewis et al. (2010), who reported less than 7 percent visual injury to zoysiagrass following three applications of Acclaim Extra or Fusilade II tank-mixed with Turflon Ester at monthly intervals. However, Tenacity tank-mixed with Acclaim Extra or Fusilade II resulted in unacceptable injury to zoysiagrass within 2 weeks after initial treatment, and showed 80 percent and 60 percent injury respectively at 12 weeks after initial treatment. Injury symptoms to zoysiagrass were characterized as chlorosis and stunted growth (Fig 3). Subsequently, treatments containing Tenacity were not applied during the second growing season.

There was no treatment-by-location interaction in percent bermudagrass cover, and data were pooled across the two locations. At 12 weeks after initial treatment, all treatments with Acclaim Extra or Fusilade II tank-mixed with Turflon Ester or Acclaim Extra tank-mixed with Tenacity significantly reduced bermudagrass cover to 2 percent or less, compared with the untreated control (Table 1).

The Fusilade II plus Tenacity treatment resulted in statistically similar bermudagrass cover compared with control plots. Prior to herbicide applications in the second year (52 weeks after initial treatment), bermudagrass coverage in the treated plots increased slightly, indicating the need for multiple years of applications. However, all treatments with Acclaim Extra or Fusilade II plus Turflon Ester resulted in less than 1 percent bermudagrass cover by 64 weeks after initial treatment.

In comparison, bermudagrass cover in untreated plots increased to nearly 20 percent, a threefold increase during the two-year period. Plots that received Fusilade II tank-mixed with Turflon Ester showed 100 percent bermudagrass control at the end of the two-year period.

Conclusion

Our data suggest that even though Tenacity tank-mixed with Acclaim Extra suppresses bermudagrass similarly to Turflon Ester mixed with Acclaim Extra or Fusilade II, tank mixtures with Tenacity lead to unacceptable zoysiagrass injury and therefore should be avoided. Furthermore, multiple applications of Turflon Ester plus Acclaim Extra or Fusilade II can provide almost complete suppression of bermudagrass with minimal injury to zoysiagrass, but applications may be needed over multiple years to maintain suppression.

Acknowledgment

We would like to thank Rob Schaff, superintendent at the Falls Golf Course, for providing the experimental site. We also thank MVGCSA and HAGCSA for their financial support of this research.

Enzhan Song is a graduate research associate and Xi Xiong, Ph.D., is a turfgrass scientist at the University of Missouri.

This article is adapted from a publication in the online journal Applied Turfgrass Management.

References

Dunn, J.H., Warmund, M.R., and Fresenburg. 2001. Bermudagrass cold tolerance. Pages: 28-29 in: University of Missouri Turfgrass Research Report. University of Missouri, Columbia, MO.
Foy, J. H. 2001. Bermudagrass fairway renovation — why it is being done and the results that have been achieved. USGA Green Section Record, 39(4): 13-15.
Huckabay, G.H. 2008. Tufted lovegrass (Eragrostis pectinacea) and doveweed (Murdannia nudiflora) control in warm-season turfgrass. M.S. Thesis. Auburn University.
Johnson, B. J. 1992. Common bermudagrass (Cynodon dactylon) suppression in zoysia spp. with herbicides. Weed Technol. 6:813-819.
Lewis, D. F., McElroy, J. S., Sorochan, J. C., Mueller, T. C., Samples, T. J., and Breeden, G. K. 2010. Efficacy and safening of aryloxyphenoxypropionate herbicides when tank mixed with triclopyr for bermudagrass control in zoysiagrass turf. Weed Technol. 24:489-494.
McElroy, J. S. and G.K. Breeden. 2006. Triclopyr safens the use of fluazifop and fenoxaprop on zoysiagrass while maintaining bermudagrass suppression. Online. Appl. Turfgrass Sci.
Shaver, B. R., Richardson, M. D., McCalla, J. H., Karcher, D. E., and Berger, P. J. 2006. Dormant seeding bermudagrass cultivars in a transition-zone environment. Crop Sci. 46:1787-1792.
Teuton, T. C., Unruh, J. B., Brecke, B. J., Miller, G. L., and Mueller, T. C. 2005. Hybrid bermudagrass (Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy) control with glyphosate and fluazifop. Online. Appl Turfgrass Sci. doi:10.1094/ATS-2005-0119-01-RS.
Willis, J.B., D.B. Richer, and S.D. Askew. 2006. Selective bermudagrass control in cool-season turfgrass with mesotrione, triclopyr and fenoxaprop. Proceedings: Northeastern Weed Science Society. Vol. 60:90.



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