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North Carolina Turfgrass – Tyler Carr, John Sorochan, and Jim Brosnan, Dept. of Plant Sciences, University of Tennessee

Zoysiagrass is a warm-season turfgrass used on lawns and golf courses in the transition zone and southern United States. Zoysiagrasses have become popular in part because they require fewer inputs and offer enhanced cold and shade tolerance compared to bermudagrass (Cynodon spp.). On golf course fairways, tees, and roughs, two different species of zoysiagrass are most common: Zoysia japonica (e.g., ‘Meyer’, ‘El Toro’, etc.) and Z. matrella (e.g., ‘Zeon’, Zorro’, etc.) (Patton et al., 2017). Continued turfgrass breeding efforts have sparked an interest in zoysiagrass for use on putting greens.

In 1996, ‘Diamond’ (Z. matrella) was released as a fine-textured zoysiagrass with potential to be used on putting surfaces; however, research from Clemson University determined that ball roll speeds were too slow for tournament purposes (Engelke et al., 2002; Stiglbauer et al., 2009). More recently, three Z. matrella cultivars [‘Prizm’ (M60), ‘Primo’ (M85), and ‘Trinity’ (L1F)] have been released for use on putting greens in addition to ‘Lazer’ (DALZ 1308), a first-generation hybrid of Z. matrella and Z. minima (Doguet and Lehman, 2014; Doguet et al., 2016, 2017; Chandra et al., 2020). These improved zoysiagrasses were planted at the University of Tennessee (Knoxville, TN) in 2018 to study their potential for use on putting greens over multiple seasons. This article will provide a brief overview of what has been learned in that research effort.

Nitrogen (N) Fertilizer Requirements and Green Speed

One of the major topics surrounding zoysiagrass management on putting greens is N fertilizer requirements. A 16-week study in 2020 compared the performance and quality of Prizm, Primo, Trinity, and Lazer when receiving annual N rates of 1.5 or 3 lb N 1000 ft^-2 (0.19 or 0.38 lb N 1000 ft^-2 every two weeks during summer) supplied as urea. All plots were mowed at a 0.115” height of cut with a walk-behind reel mower (Greensmaster Flex 2100, The Toro Company, Bloomington, MN).

Most golf course superintendents are very familiar with using a Stimpmeter to provide a measure of green speed (i.e., ball roll distance; Radko, 1980). When mowing and rolling five times weekly, green speeds for all zoysiagrasses tested averaged at least 10.5’ over the 16-week study period, even when receiving 3 lb N 1000 ft^-2 (Figure 1). In general, the 3 lb N 1000 ft^-2 rate resulted in superior color compared to 1.5 lb N 1000 ft^-2 (Figure 2) while still maintaining green speeds greater than those historically reported for Diamond. Further testing of other annual N rates between 1.5 and 3 lb 1000 ft^-2 will be needed to determine the specific amount of N required to maintain acceptable quality and optimal green speed on zoysiagrass putting greens in Tennessee. Nonetheless, the range of N rates tested in this study provides a starting point for golf course superintendents considering renovating to zoysiagrass putting surfaces.

Bermudagrass Encroachment

Aside from managing zoysiagrass for performance, golf course superintendents will likely face encroachment from another warm-season turfgrass, bermudagrass. Controlling bermudagrass in Z. japonica typically involves multiple applications of Fusilade II (fluazifop) + Turflon Ester (triclopyr) (Brosnan et al., 2011); however, the tolerance of greens-type zoysiagrass to this treatment is unknown. A two-year study was initiated in August 2020 at the University of Tennessee and the University of Arkansas to evaluate the tolerance of Prizm and Lazer zoysiagrass to several postemergence herbicides including Fusilade II (4 fl oz/A), Turflon Ester (32 fl oz/A), Fusilade II (4 fl oz/A) + Turflon Ester (32 fl oz/A), Revolver (26.2 fl oz/A), and Dismiss NXT (8 fl oz/A).

Unlike Z. japonica, both Fusilade II + Turflon Ester and Turflon Ester alone resulted in unacceptable and prolonged injury to both Prizm and Lazer zoysiagrass. Interestingly, Fusilade II applied alone resulted in limited injury (Figure 3). The same negative effects of Turflon Ester and acceptable tolerance of Fusilade II have been previously reported for Diamond zoysiagrass (Lewis et al., 2010). Additionally, Revolver was safe on Prizm and Lazer whereas Dismiss NXT resulted in unacceptable injury. These treatments will be applied again in 2021 at both locations to make sure responses are consistent over time. As zoysiagrass use on putting greens increases, additional research will be needed to understand tolerance of greens-type cultivars to other herbicides, fungicides, and insecticides used for pest management.

Establishment

The single greatest concern golf course superintendents express about renovating putting greens to zoysiagrass is the slow establishment from sprigs (8-12 weeks) compared to ultradwarf bermudagrass (6-8 weeks). A major research focus at the University of Tennessee is to explore methods to hasten zoysiagrass establishment from sprigs. A field study evaluating establishment of Prizm zoysiagrass in April, May, June, and July was initiated in 2020 and is being repeated in 2021. In this study, Prizm zoysiagrass was sprigged at 1200 bushels/A at each timing. One week prior to sprig harvesting, Lexicon (21 fl oz/A) was applied to established Prizm zoysiagrass at Bladerunner Farms (Poteet, TX). Before planting sprigs, starter fertilizer (18-24-12) was applied to the experimental area at 0.5 lb P₂O₅ 1000 ft^-2 and organic fertilizer (6-2-0; Milorganite Classic, Milorganite, Milwaukee, WI) was applied at 0.25 lb N 1000 ft^-2 totaling 0.63 lb N 1000 ft^-2, 0.58 lb P₂O₅ 1000 ft^-2, and 0.25 lb K₂O 1000 ft^-2. Additionally, Ronstar Flo (80 fl oz/A) was applied immediately prior to planting. During establishment, irrigation was applied five times daily replacing 150% of the previous day’s evapotranspiration, which was estimated using the mesur.io Earthstream platform (mesur.io, Yanceyville, NC).

Planting date affected establishment in 2020, as establishment rates increased with planting month (Figure 4). However, Prizm zoysiagrass planted in June and July did not fully establish in 2020, which was likely a result of fall temperatures that were not conducive for warm-season turfgrass growth. Prizm planted in late spring (April or May) had slower establishment rates than the summer plantings but established fully in the same growing season. Planting Prizm sprigs in early summer and at rates greater than those used in this study could accelerate establishment and warrants further investigation, as several golf courses have shown success when establishing zoysiagrass sprigs at rates of 1800 to 2000 bu/A.

The effect of preplant herbicides on Prizm establishment was tested in May 2020 and repeated in May 2021 using the same, previously described, establishment methodology. Treatments tested included Ronstar Flo (122 fl oz/A), Tower (32 fl oz/A), Regalstar II (200 lb/A), Anderson’s Crabgrass and Goosegrass Control (305 lb/A), and an experimental herbicide from PBI Gordon. Anderson’s Crabgrass and Goosegrass Control and Regalstar II both severely prolonged establishment, which was not unexpected given the active ingredients in those herbicides. An application of Tower before planting hastened establishment compared to the non-treated control (Figure 5).

Conclusion

While much has been learned about managing new zoysiagrass cultivars on putting greens over the past 18 months, many things still remain unknown and warrant further research. The University of Tennessee will be diligently working to learn more about these grasses to support golf course superintendents considering a renovation to zoysiagrass in the future. For more information on our work, please connect with us on Twitter (@UTturfgrass) or visit the University of Tennessee Turfgrass Science & Management Website, https://plantsciences.tennessee.edu/turfgrass/.

Tyler Carr, Graduate Research Assistant (@TylerTalksTurf)

John Sorochan, Distinguished Professor (@Sorochan)

Jim Brosnan, Professor and Director (@UTturfweeds)

References

Brosnan, J., Breeden, G., Elmore, M., & Zidek, J. (2011). Application timing affects bermudagrass suppression with mixtures of fluazifop and triclopyr. Weed Technology, 25, 591–597. https://doi.org/10.1614/WT-D-10-00165.1

Chandra, A., Genovesi, A. D., Meeks, M., Wu, Y., Engelke, M. C., Kenworthy, K., & Schwartz, B. (2020). Registration of ‘DALZ 1308’ zoysiagrass. Journal of Plant Registrations, 14, 19–34. https://doi.org/10.1002/plr2.20016

Doguet, D., Doguet, D. A., & Lehman, V. G. (2016). Zoysiagrass plant named ‘M85’. US Plant Patent 27289. Date issued: 18 October.

Doguet, D., Doguet, D. A., & Lehman, V. G. (2017). Zoysiagrass plant named ‘M60’. US Plant Patent 29143. Date issued: 23 November.

Doguet, D., & Lehman, V. (2014). Zoysiagrass plant named ‘L1F’. US Plant Patent 25203. Date issued: 30 December.

Engelke, M. C., Colbaugh, P. F., Reinert, J. A., Marcum, K. B., White, R. H., Ruemmele, B., & Anderson, S. J. (2002). Registration of ‘Diamond’ zoysiagrass. Crop Science, 42, 304–305. https://doi.org/10.2135/cropsci2002.3040

Lewis, D., McElroy, J., Sorochan, J., Mueller, T., Samples, T., & Breeden, G. (2010). Efficacy and Safening of Aryloxyphenoxypropionate Herbicides when Tank-Mixed with Triclopyr for Bermudagrass Control in Zoysiagrass Turf. Weed Technology, 24, 489-494. https://doi.org/10.1614/WT-D-10-00029.1

Patton, A. J., Schwartz, B. M., & Kenworthy, K. E. (2017). Zoysiagrass (Zoysia spp.) history, utilization, and improvement in the United States: A review. Crop Science, 57, 37–72. https://doi.org/10.2135/cropsci2017.02.0074

Radko, A. (1980). The USGA Stimpmeter for Measuring the Speed of Putting Greens. In J.B. Beard (Ed.), Proceedings of The Third International Turfgrass Research Conference (pp. 473–476). American Society of Agronomy, Crop Science Society of America, Soil Science Society of America.

Stiglbauer, J. B., Liu, H., McCarty, L. B., Park, D. M., Toler, J. E., & Kirk, K. (2009). ‘Diamond’ zoysiagrass putting green establishment affected by sprigging rates, nitrogen sources, and rates in the southern transition zone. HortScience, 44, 1757–1761. https://doi.org/10.21273/hortsci.44.6.1757