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© 2005 Plant Management Network.
Accepted for publication 28 June 2005. Published 18 July 2005.

Tolerance of ‘Riviera’ Bermudagrass to MSMA Tank-Mixtures with Postemergence Herbicides During Establishment from Seed

Michael D. Richardson and Douglas E. Karcher, Associate Professors, Department of Horticulture, University of Arkansas, Fayetteville 72701; John W. Boyd, Extension Weed Scientist, Cooperative Extension Service, University of Arkansas, Little Rock 72203; and John H. McCalla and Josh W. Landreth, Research Specialists, Department of Horticulture, University of Arkansas, Fayetteville 72701

Corresponding author: Michael D. Richardson. mricha@uark.edu

Richardson, M. D., Karcher, D. E., Boyd, J. W., McCalla, J. H., and Landreth, J. W. 2005. Tolerance of ‘Riviera’ bermudagrass to MSMA tank-mixtures with postemergence herbicides during establishment from seed. Online. Applied Turfgrass Science doi:10.1094/ATS-2005-0718-01-RS.

Abstract

Seeded bermudagrass (Cynodon dactylon L. Pers.) cultivars are rapidly gaining popularity in the turfgrass industry. Management programs need to be developed for the proper establishment and maintenance of these seeded cultivars. The objective of this study was to determine the tolerance of seedling ‘Riviera’ bermudagrass to a range of postemergence herbicides. Herbicide treatments were applied at 2 and 4 weeks after emergence and included metribuzin + MSMA, triclopyr + clopyralid + MSMA, clopyralid + MSMA , flazasulfuron + MSMA, foramsulfuron + MSMA, trifloxysulfuron-sodium + MSMA, quinclorac + MSMA, 2,4-D + dicamba + mecoprop + MSMA, and quinclorac. Herbicide injury and turfgrass coverage rates were monitored for 4 weeks after treatment. Treatments that caused significant injury to the seedling turf included metribuzin + MSMA and triclopyr + clopyralid + MSMA. Most of the herbicide combinations tested in these trials caused some level of turfgrass injury, but this injury was generally short-lived and did not significantly reduce the rate of turfgrass coverage. The results of this study indicate that a range of herbicide combinations can be safely used on seedling bermudagrass to control problematic weeds during establishment.

Introduction

Bermudagrass (Cynodon spp.) continues to be the major turfgrass species for golf courses, sports fields, lawns, and utility turf areas in southern and transition-zone regions of the United States. In the past decade, several new seeded bermudagrass cultivars (C. dactylon L. Pers.) have been developed that have enhanced performance over older, common types of bermudagrass (1,9). As these new cultivars gain acceptance in the turfgrass industry, management programs need to be developed that address specific issues related to seed propagation of bermudagrass.

The ability to control weeds during the first weeks after emergence will be a key factor to the success of these new seeded bermudagrasses. Summer annual grasses such as crabgrass (Digitaria spp (L.) Scop.) and goosegrass (Eleusine indica (L.) Gaertn.) are very competitive among bermudagrass seedlings and various broadleaf weeds and sedges may also create problems through shading of young bermudagrass seedlings. Therefore, competition during the seedling stage could significantly prolong stand establishment and reduce overall stand density.

Numerous studies have investigated the efficacy and safety of postemergence herbicides on established bermudagrass turf and many postemergence strategies are available for control of major weed species common to bermudagrass (3,7,10). However, quinclorac (3, 7-dichloro-8-quinolinecarboxylic acid) is the only postemergence herbicide that is labeled for use during seedling establishment of bermudagrass and previous studies have confirmed its safety (6,8). Recently, the safety of other postemergence herbicides on seedling bermudagrass has also been investigated in an attempt to broaden the spectrum of herbicides available for use during establishment of these grasses (6,8). Of the herbicides tested in those studies, MSMA (monosodium salt of methylarsonic acid) had good safety on seedling bermudagrass (6) and is an effective herbicide for controlling problematic, grassy weeds such as crabgrass. However, label recommendations for this product state that it is not to be used on seedling turfgrass until the turf has been mown three times.

As new herbicides continue to be developed for the turfgrass market, it would be desirable to identify additional products that can be safely used to control grass and broadleaf weeds in seedling bermudagrass. Since MSMA continues to be a major postemergence herbicide for crabgrass control, tank-mixes that include this herbicide would provide a solid foundation to control crabgrass and other problematic weeds in seedling bermudagrass. The objective of this study was to evaluate the tolerance of a seeded bermudagrass (cv. Riviera) to nine postemergence herbicide treatments applied at two periods after emergence.

Field Analysis of Herbicide Tolerance on ‘Riviera’ Bermudagrass

A field study was conducted over two growing seasons (2003 and 2004) at the University of Arkansas Research and Extension Center, Fayetteville, AR. The soil at the site is a captina silt loam (fine-silty, siliceous, active, mesic Typic Fragiudults) with an average pH of 6.2. Prior to planting, the site was fumigated with methyl bromide (67%) and chloropicrin (33%) at 392 kg/ha. Fumigation of the soil provided a weed-free seed bed so injury effects of various herbicides and establishment rates of the bermudagrass could be more easily measured.

‘Riviera’ bermudagrass was broadcast seeded at 48 kg of pure live seed per ha in a prepared seed bed on 15 June 2003 and 1 June 2004. The site was irrigated to provide optimum moisture conditions for germination and establishment of the seed and to prevent water stress. Plots were amended with phosphorous and potassium prior to planting according to soil test recommendations. Nitrogen was applied as urea (46-0-0) at a rate of 48 kg of N per ha, beginning 14 days after first emergence, and re-applied every 4 weeks during the test. Beginning at 28 days after emergence, plots were mowed three times a week with a reel mower set to a bench height of 1.5 cm with clippings returned.

Nine postemergence herbicide treatment combinations were applied at 2 and 4 weeks after emergence (WAE) at a rate in compliance with the manufacturer’s label (Table 1). Treatments included the following herbicides: clopyralid (3,6 dichloro-2-pyridinecarboxylic acid); dicamba (3,6-dichloro-2-methoxybenzoic acid); 2,4-D amine D [(2,4 - dichlorophenoxy) acetic acid; quinclorac (3, 7-dichloro-8-quinolinecarboxylic acid); metribuzin (4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4,-triazin-5(4H)-one); triclopyr ([(3,5,6-trichloro-2-pyridinyl)oxy]acetic acid); mecoprop (2-(4-chloro-2-methylphenoxy) propanoic acid); flazasulfuron (1-(4,6-dimethoxypyrimidin-2-yl)-3-(3-trifluoromethyl-2-pyridylsulfonyl)urea); foramsulfuron (1-(4,6-dimethoxypyrimidin-2-yl)-3-[2-(dimethylcarbamoyl)-5-formamidophenylsulfonyl]urea); and trifloxysulfuron (1-(4,6-dimethoxypyrimidin-2-yl)-3-[3-(2,2,2-trifluoroethoxy)-2-pyridylsulfonyl]urea). All herbicide treatments included MSMA at 2.24 kg/ha while quinclorac was also included alone as a standard check for safety. Herbicides were applied as a broadcast spray with a CO₂ sprayer at 374 liters/ha. Plot size was 1.2 × 1.5 m. Four plots were maintained as untreated controls within each season and application timing.

Table 1. Postemergence herbicide treatments and rates applied to ‘Riviera’ seeded bermudagrass at 2 and 4 weeks after emergence.

Visual injury ratings were taken on all plots at 3, 5, 7, 10, 14, 21, and 28 days after treatment (DAT) and percentage turfgrass cover was assessed at 7, 14, 21 and 28 DAT using digital image analysis (12). Visual injury ratings were taken using a scale from 0 to 9 with 0 being no injury and 9 being death of all plants. A score of 3 or less was considered an acceptable level of injury. Herbicide treatments were arranged as a 9 × 2 factorial (nine herbicide combinations and two application timings) in a randomized complete block design with four replications. Since each evaluation was made repeatedly on a given plot over time, a third factor, DAT, was included in a repeated measures analysis. Preliminary data analysis indicated that an autoregressive (order 1) covariance model best described the correlation of observations on the same plots across evaluation dates (5). Accordingly, evaluation parameters were analyzed using this model in PROC MIXED, SAS v. 9.1 (SAS Institute, Inc., Cary, NC) to determine if the effects of year, herbicide treatment, timing, DAT, and their interactions were significant (P < 0.05). When effects were significant, treatment means were separated according to Fisher’s protected least significant difference test (13). In addition, all interaction effects containing DAT were sliced by DAT to determine specific dates when treatment differences were significant (SAS Institute, Inc., Cary, NC).

Herbicide Injury on Seedling ‘Riviera’ Bermudagrass

Herbicide injury observed in this study consisted of general yellowing or other discoloration of the bermudagrass leaves. There was a significant 4-way interaction of year, herbicide, timing of applications, and days after treatment on herbicide injury (data not shown).

Timing of application had a significant effect on herbicide injury for several of the herbicides tested in 2003, including quinclorac, quinclorac + MSMA, metribuzin + MSMA, 3-way + MSMA, clopyralid + triclopyr + MSMA, trifloxysulfuron + MSMA, and flazasulfuron + MSMA (Fig. 1). In general, higher levels of injury were observed with the 2 WAE timing compared to the 4 WAE timing for those herbicides. The 2 WAE treatment of quinclorac + MSMA caused significantly higher levels of injury than the 4 WAE treatment at 5, 7, and 10 DAT (Fig. 1), but the actual differences in injury between timings were small and had no effect on turfgrass establishment rates (discussed below). Similar trends were observed with the clopyralid + triclopyr + MSMA treatment (Fig. 1).

Fig. 1. Herbicide injury on ‘Riviera’ bermudagrass as affected by application timing and herbicide treatments (2003 data). Herbicides were applied at either 2 or 4 weeks after emergence (WAE) and injury was rated on a scale of 0 to 9, with 0 = no injury and 9 = complete death of seedlings. An injury rating of 3 or less was considered an acceptable level of injury. Asterisks indicate evaluation dates where herbicide injury was significantly different between timings, as determined by Fisher’s Protected LSD (P = 0.05).

In 2004, the differences due to timing were generally smaller and were only observed on a few evaluation dates throughout the study (Fig. 2). The effects of timing were primarily significant at 10 DAT, where the 4 WAE timing had greater injury than the 2 WAE timing (Fig. 2). One possible explanation for this difference was cooler than normal temperatures during the early part of the study in 2004, especially when the 2 WAE treatments were applied. Temperatures increased during the 4 WAE treatment period and may have contributed to slightly more injury during that timeframe. Nonetheless, timing effects were not significant at other evaluation dates and did not appear to be major factor for herbicide injury.

Fig. 2. Herbicide injury on ‘Riviera’ bermudagrass as affected by application timing and herbicide treatments (2004 data). Herbicides were applied at either 2 or 4 weeks after emergence (WAE) and injury was rated on a scale of 0 to 9, with 0 = no injury and 9 = complete death of seedlings. An injury rating of 3 or less was considered an acceptable level of injury. Asterisks indicate evaluation dates where herbicide injury was significantly different between timings, as determined by Fisher’s Protected LSD (P = 0.05).

The most dramatic timing effect was observed in 2003 with metribuzin + MSMA, where maximum injury ratings of 8.0 were observed with the 2 WAE timing compared to 5.0 with the 4 WAE timing (Figs. 1 and 3) and those timing differences remained for 21 DAT. For the 3-way + MSMA treatment in 2003, the 2 WAE timing was much slower to recover compared to the 4 WAE and significant differences were observed up to 14 DAT (Fig. 1). Flazasulfuron also caused more injury at the 2 WAE timing than the 4 WAE timing in 2003 (Fig. 1) and these differences were observed up to 14 DAT.

Fig. 3. Herbicide injury observed on ‘Riviera’ bermudagrass at 3 days after treatment in the 2003 trial, applied at 2 weeks after emergence. Herbicide treatments include quinclorac (A), metribuzin + MSMA (B), 3-way broadleaf + MSMA (C), and untreated control (D).

When the effects of herbicide were evaluated by timing in 2003 and 2004, metribuzin + MSMA was the only herbicide combination that caused unacceptable levels of injury for an extended period (Figs. 3 and 4). All of the herbicides caused some level of injury soon after application (Fig. 4), but the bermudagrass recovered quickly and most of the injury remained below acceptable levels throughout the evaluation period. Quinclorac generally caused the least amount of injury in both the 2 WAE and 4 WAE timings in 2003 and 2004 (Figs. 3 and 4).

Fig. 4. Herbicide injury on ‘Riviera’ bermudagrass as affected by eight postemergence herbicide combinations applied at either 2 or 4 weeks after emergence (WAE) during 2003 and 2004. Injury was rated on a scale of 0 to 9, with 0 = no injury and 9 = complete death of seedlings. An injury rating of 3 or less was considered an acceptable level of injury. For comparing means within each graph, the interaction LSD = 1.01.

For those herbicides that are used to control grassy weeds, quinclorac had good safety on seedling bermudagrass (Figs. 1 through 4), which is in agreement with earlier reports (6,8,11). When quinclorac was tank-mixed with MSMA, herbicide injury was increased (Fig. 4), but injury remained at or below acceptable levels. Metribuzin + MSMA caused significant damage to the seedling bermudagrass in both years of the trial (Figs. 1 through 4), although the injury was greater in the 2003 trial compared to 2004 (Fig. 4).

Although this is the first report of seedling bermudagrass tolerance to metribuzin + MSMA, McElroy and co-workers (8) reported very high levels of injury on seedling bermudagrass with atrazine, a herbicide with a similar mode of action to metribuzin. This herbicide combination also causes a significant reduction in turfgrass quality when applied to mature common bermudagrass types (3,4,7). Although metribuzin + MSMA is used to control goosegrasss in established bermudagrass (2), the level of injury observed on seedling bermudagrass would make this an unacceptable combination to use during the first few weeks of establishment.

Broadleaf herbicides caused modest levels of injury to seedling ‘Riviera,’ but only exceeded unacceptable levels of injury on two of fourteen evaluation dates. The 3-way herbicide (2,4-D, dicamba and mecoprop) + MSMA caused significant discoloration of the turf for up to 14 DAT, but the turf had fully recovered by 21 DAT (Figs. 1, 2, and 4). These findings are similar to those reported by McElroy et al. (8) on four seeded bermudagrass cultivars, including ‘Riviera.’ The clopyralid + triclopyr + MSMA treatment caused slightly higher injury ratings compared to the clopyralid + MSMA (Fig. 4). Other researchers reported a 10% injury rating with clopyralid + triclopyr on juvenile ‘Riviera’ bermudagrass (8) which is similar to the injury observed in the present trial (Figs. 1, 2, and 4). Mature common bermudagrass has also shown tolerance of clopyralid and clopyralid + triclopyr combinations (14).

Most of the broadleaf herbicides tested in this trial and by other researchers (6,8) appear to have relatively good safety on seeded bermudagrass during establishment. Quinclorac also has good activity on numerous broadleaf weeds and has excellent safety on seedling bermudagrass (6,8,11). Therefore, a number of herbicide combinations are available to control both annual and perennial broadleaf weeds during the establishment of seeded bermudagrass.

Three herbicides tested in this trial fall under the sulfonylurea class of herbicide, including foramsufuron, trifloxysulfuron, and flazasulfuron. These herbicides, in combination with MSMA, caused relatively low levels of injury to ‘Riviera’ bermudagrass (Figs. 1, 2, and 4). Most of the injury was observed within the first 14 DAT and was not present at 21 DAT. The level of herbicide injury was similar for all three herbicides tested from this group (Fig. 4). Earlier trials at this location with metsulfuron revealed similar results on this and other seeded bermudagrass cultivars (6). Foramsulfuron and trifloxysulfuron were tested in a previous trial against four seeded bermudagrass cultivars, including ‘Riviera,’ and found to have good safety when applied at 4 to 7 weeks after emergence (8). The present trial would indicate that these herbicides can be safely used on seedling bermudagrass as early as 2 weeks after emergence. The sulfonylurea herbicides have shown excellent herbicidal activity against a range of cool-season grasses and sedges (15) and will be a safe option to use on seedling bermudagrass turf. Foramsulfuron has also shown to have good activity against goosegrass (2) and will be a much safer option during seedling establishment than metribuzin + MSMA or diclofop (6).

Turfgrass Establishment Rates of ‘Riviera’ Bermudagrass as Affected by Herbicides

There was a significant year × herbicide × timing × days after treatment interaction on turfgrass coverage (data not shown). Although injury was observed with many of the herbicide combinations, turfgrass cover was only reduced by a few of the treatment combinations (Fig. 5). During the 2003 trial, metribuzin + MSMA caused the greatest reduction in turfgrass coverage, regardless of timing, and was significantly different from the untreated control at 7 and 14 DAT (Fig. 5). In addition, a significant reduction in turfgrass coverage was also observed at 21 and 28 DAT for the 2 WAE treatments. The 4 WAE timing recovered more quickly from the metribuzin + MSMA treatment and was not significantly different from the control by 21 DAT. In the 2004 trial (Fig. 5), a significant reduction in turfgrass coverage was again observed at 7 and 14 DAT, but the turf had fully recovered by 21 DAT. It is apparent from these data that the s-triazine and triazinone classes of herbicides can be more safely used on bermudagrass seedlings once they begin to develop stolons (4 to 7 weeks after emergence), as described earlier (8).

Fig. 5. Turfgrass coverage of ‘Riviera’ bermudagrass as affected by eight postemergence herbicide combinations applied at either 2 or 4 weeks after emergence (WAE) during 2003 and 2004. Turfgrass coverage was measured using digital image analysis techniques. For comparing means within each graph, the interaction LSD = 7.13.

Another herbicide combination that caused a significant reduction in turfgrass establishment rate was clopyralid + triclopyr + MSMA. In the 2003 trial, a significant reduction in turfgrass coverage was observed at 7 DAT for both application timings and at 14 DAT for the 4 WAE timing (Fig. 5). In the 2004 trial, there was no negative effect of clopyralid + triclopyr + MSMA on turfgrass establishment rate (Fig. 5).

The 3-way broadleaf + MSMA and flazasulfuron + MSMA treatments caused a reduction in turfgrass establishment at 7 DAT in the 2003 trial when applied at 2 WAE (Fig. 5). However, this reduction was not observed in the 4 WAE timing in 2003 or 2004 trials (Fig. 5), suggesting that reductions in establishment observed in this trial would be considered nominal when using these herbicide combinations.

Conclusions

The herbicide combinations tested in these trials caused varying levels of turfgrass injury to ‘Riviera’ bermudagrass, but this injury was generally short-lived and did not significantly reduce the rate of turfgrass coverage in most treatments. These data are complimentary to earlier work done at this location on seeded bermudagrass, which showed good to excellent tolerance to many postemergence herbicides during the establishment period (6,8). These treatments offer broad-spectrum control for many of the problematic weeds that can reduce bermudagrass establishment.

Acknowledgments

The authors would like to thank the United States Golf Association, the Golf Course Superintendents Association of America, and the Golf Course Superintendents Association of Arkansas for their financial support of this research.

Literature Cited

1. Anderson, J. A., Taliaferro, C. M., and Martin, D. L. 2003. Longer exposure durations increase freeze damage to turf bermudagrasses. Crop Sci. 43:973-977.

2. Busey, P. 2004. Goosegrass (Eleusine indica) control with foramsulfuron in bermudagrass (Cynodon dactylon) turf. Weed Tech. 17:550-553.

3. Johnson, B. J. 1995. Tolerance of four seeded common bermudagrass (Cynodon dactylon) types to herbicides. Weed Tech. 9:794-800.

4. Johnson, B. J. 1997. Tank-mixed postemergence herbicides for postemergence goosegrass control in bermudagrass turf. J. Env. Hort. 15:33-36.

5. Littell, R. C., Pendergast, J., and Natarajan, R. 2000. Modelling covariance structure in the analysis of repeated measures data. Statist. Med. 19:1793-1819.

6. McCalla, J. H., Richardson, M. D., Boyd, J. W., and Karcher, D. E. 2004. Tolerance of seedling bermudagrass to postemergence herbicides. Crop Sci. 44:1330-1336.

7. McCarty, L. B., Miller, L. C., and Colvin, D. L. 1991. Bermudagrass (Cynodon spp.) cultivar response to diclofop, MSMA, and metribuzin. Weed Tech. 5:27-32.

8. McElroy, J. S., Breeden, G. K., Yelverton, F. H., Gannon, T. W., Askew, S. D. and Derr., J. F. 2005. Seeded bermudagrass response to herbicides during establishment. Golf Course Mgmt. 73:154-158.

9. Munshaw, G. C., Williams, D. W., and Cornelius, P. L. 2001. Management strategies during the establishment year enhance production and fitness of seeded bermudagrass stolons. Crop Sci. 41:1558-1564.

10. Murdoch, C. L., and Ikeda, D. 1974. Goosegrass control in bermudagrass turf with combinations of MSMA and s-triazines. Agron. J. 66:712-714.

11. Patton, A., Williams, D. W., and Reicher, Z. J. 2004. Establishing seeded bermudagrass. Golf Course Mgmt. 72:73-77.

12. Richardson, M. D., Karcher, D. E., and Purcell, L. A. 2001. Using digital image analysis to quantify percentage turfgrass cover. Crop Sci. 41:1884-1888.

13. Steel, R. G., and Torrie, J. H. 1980. Principles and Procedures of Statistics. McGraw-Hill Book Company, New York, NY.

14. Tucker, B. J., Higingbottom, J. K., and McCarty, L. B. 2002. Tolerance to fluroxypyr and clopyralid in bermudagrass (Cynodon dactylon) and St. Augustinegrass (Stenotaphrum secundatum). South. Weed Sci. Soc. Proc. 55:67-68.

15. Yelverton, F. 2003. A new herbicide for weeds in bermudagrass and zoysiagrass. Golf Course Mgmt. 71:119-122.