Douglas E. Karcher

Drought Tolerance of Kentucky Bluegrass and Hybrid Bluegrass Cultivars

The development of drought-tolerant turf cultivars can have a positive impact on future water resources. The objective of the following research was to evaluate the field drought tolerance of nine Kentucky bluegrass (Poa pratensis L.) cultivars and eighteen hybrid bluegrass (primarily P. pratensis × P. arachnifera Torr.) cultivars. The bluegrass entries were established in the field in Albany, OR, and evaluated under drought stress in the summer of 2006 and 2007. Drought tolerance and recovery following drought were measured using digital image analysis and were defined as the number of days until a cultivar reached 50% green tissue. Several Kentucky bluegrass cultivars, including Mallard, Bluestone, and Arrow, demonstrated significantly better drought tolerance than other Kentucky bluegrass and hybrid bluegrass cultivars. One hybrid bluegrass cultivar, Longhorn, and several experimental hybrids, had excellent drought tolerance in this trial. However, many of the hybrids tested in this trial did not have superior drought tolerance characteristics compared to the Kentucky bluegrasses tested. These results demonstrate that there is wide variability in drought tolerance among both Kentucky bluegrass and hybrid bluegrass and the broad screening of this genetic material under limited water can provide turfgrass managers with selections that can ultimately conserve water. In addition, these results demonstrate that there are no clear differences in drought tolerance between hybrid bluegrasses and Kentucky bluegrass.

Bermudagrass and Zoysiagrass Cultivar Selection: Part 2, Divot Recovery

Golfers commonly remove turf and soil when swinging a golf club causing a divot in the turf. Divot recovery is an important factor that should be considered when selecting a species or cultivar for use on golf course tees or fairways. There are few reports directly comparing the divot recovery among bermudagrass (Cynodon spp. Rich.) and zoysiagrass (Zoysia spp. Willd.) cultivars. Therefore, the objective of this experiment was to quantify divot recovery of several bermudagrass and zoysiagrass cultivars in a combined field experiment. Divot recovery was evaluated on four collection dates for five cultivars of bermudagrass and seven cultivars of zoysiagrass. Cultivars generally with the fastest time to 50% recovery were ‘Princess 77’ and ‘Riviera’ bermudagrass and ‘Palisades’ zoysiagrass. Generally, the cultivars with the slowest time to 50% recovery were ‘Meyer’ and ‘Zenith’ zoysiagrass. Additionally, ‘Tifway’ bermudagrass had similar divot recovery times to ‘El Toro’ and Palisades zoysiagrass. These results demonstrate that differences and similarities exist among bermudagrass and zoysiagrass cultivars for divot recovery, and golf course superintendents can use this information to better select cultivars that could improve surface playing conditions. Introduction A swing by a golfer while attempting to strike a golf ball commonly displaces an area of turf and soil that is referred to as a divot (7). Divots created by a golf stroke are a regular occurrence on golf course fairways or tees (7). It has been estimated that approximately 0.21 ha of turf are removed by divoting from a bermudagrass golf course fairway each year (7). The number, size, and length of time divots exist on a tee or fairway depend on species (1). Divot recovery describes the rate of recovery of a turfgrass from divoting and is an important factor that should be considered when selecting a species or cultivar for use on golf course tees or fairways and other athletic playing fields. There have been few studies to quantify differences in recovery rates between species, but popular turf textbooks (1,10) rank bermudagrass (Cynodon spp.) as having superior recuperative capacity or rate compared to zoysiagrass (Zoysia spp.). Karcher et al. (4,5) examined the divot recovery on native soil for numerous bermudagrass and zoysiagrass cultivars in separate field studies. Karcher et al. (4) reported that Riviera, Princess 77, and ‘Patriot’ bermudagrass each had relatively fast divot recoveries for the cultivars tested during the first year of the experiment. However, in the second year’s results, there were no differences among Princess 77, Riviera, Tifway, ‘Tifsport,’ and Patriot bermudagrass. In a separate study evaluating zoysiagrass cultivars, Karcher et al. (5) reported that Palisades, ‘Cavalier,’ Zenith, and ‘Zorro’ zoysiagrass all had similar divot recovery, while Meyer had a significantly slower divot recovery. El Toro had the fastest divot recovery in one year of the study, but had a relatively slower divot recovery in another year. Although bermudagrass and zoysiagrass were evaluated in separate experimental areas by Karcher et al. (4,5), their data 30 June 2011 Applied Turfgrass Science suggest that the recuperative capacity of these two species may not be as different as previously reported (1,10). For example, in 2004 Karcher et al. (4) reported that Riviera bermudagrass required 4.6 days to reach 50% recovery, while in 2004 Karcher et al. (5) reported that Palisades zoysiagrass required 4.2 days to reach 50% recovery. It has also been reported that zoysiagrass cultivars can differ greatly in growth rate and establishment rate (6), suggesting that some zoysiagrass cultivars may also have divot recovery similar to specific bermudagrass cultivars. Therefore, the objective of this experiment was to quantify the divot recovery for commonly used bermudagrass and zoysiagrass cultivars in the same experimental field trial. Evaluating Divot Recovery This experiment was conducted at the Arkansas Agricultural Research and Extension Center, in Fayetteville, AR (36°06’N, 94°10’W, 384 m). The planting site was fumigated with methyl bromide at 549 kg/ha in April 2007 and was a Captina silt-loam soil (fine-silty mixed mesic Typic Fragiudalt) with a pH of 6.6, 1% organic matter, 105 kg P/ha, and 97 kg K/ha. Five cultivars of bermudagrass and seven cultivars of zoysiagrass were evaluated in the experiment (Table 1). Cultivar selection was based on use and availability in the transition zone and southern United States. All cultivars were established as sod in July 2007 as 1.8m by 1.8-m plots with a 0.3-m border maintained with glyphosate (2.2 kg/ha) to prevent contamination from adjacent plots. Due to limited sod availability, ‘Diamond’ zoysiagrass was initially planted as 0.5-m by 0.5-m plots until additional plant material could be propagated. Diamond zoysiagrass plugs were planted in May 2008 in the remainder of the plot area and plots were > 95% cover by August 2008. To simulate golf course fairway conditions, all plots were mowed at 1.3 cm. The experimental design was a randomized complete block design with four replications. Plots were fertilized with nitrogen using urea (460-0) at 24 kg/ha per growing month for zoysiagrass and 49 kg/ha per growing month for bermudagrass based upon input from Arkansas golf course superintendents. Simazine was applied to all plots on 21 November 2007 and 24 November 2008 at 1.1 kg/ha to control winter annual weeds. An additional application of foramsulfuron was applied on 13 April 2008 at 30 g/ha to control annual bluegrass (Poa annua L.). Table 1. Cultivar, experimental notation, and species of bermudagrass and zoysiagrass used in this study to quantify divot recovery in Fayetteville, AR. x The cultivars Princess 77 bermudagrass and Zorro zoysiagrass were each evaluated using two experimental notations before the cultivars were released for commercial use. Cultivar Experimental

Water Repellency Varies with Depth and Season in Sandy Rootzones Treated With Ten Wetting Agents

A study was conducted at New Mexico State University during the summer months of 2003 and 2004 to investigate the effects of several wetting agents on sand-based rootzone hydrophobicity and putting green turf appearance. The efficacy of wetting agents varied over depth and was most pronounced at depths of 2.5 cm or less. All treated plots with the exception of Naiad and Respond 2 plots exhibited lower water repellency than the untreated plots at a depth of 0.5 cm. Plots treated with Aqueduct and LescoFlo showed consistently lower water repellency at rootzone depths of 0.5, 1.5, and 2.5 cm than the untreated plots. Naiad-treated rootzones exhibited greater hydrophobicity at depths of 0.5, 1.5, 2.5 and 3.5 cm compared to the untreated rootzones. In 2003 plots treated with Brilliance, Cascade Plus, HydroWet, LescoFlo, and Primer Select had higher turfgrass quality than the untreated plots, while Naiad-treated plots showed lower quality and color ratings than other plots. There were no differences in color or quality, among the treatments in 2004.

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

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 shortlived 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.

Bermudagrass and Zoysiagrass Cultivar Selection: Part 1, Clipping Yield, Scalping Tendency, and Golf Ball Lie

Bermudagrass (Cynodon spp. Rich.) and zoysiagrass (Zoysia spp. Willd.) are two of the most commonly used turfgrass species on golf course fairways and tees in the southern United States. However, there are few reports directly comparing commonly used cultivars of bermudagrass to commonly used cultivars of zoysiagrass. The objectives of this research were to quantify the clipping yield, percent ball exposed (ball lie), and to identify the scalping tendency for five bermudagrass and seven zoysiagrass cultivars grown in Fayetteville, AR. The cultivars generally producing the lowest clipping yields were ‘Patriot’ bermudagrass and ‘Meyer’ zoysiagrass, while ‘Tifway’ bermudagrass and ‘Palisades’ zoysiagrass generally had the highest clipping yields. On most collection dates, Cynodon spp. yielded more clippings than Zoysia spp. Patriot bermudagrass had the highest scalping tendency across the two years of this study. The cultivars Patriot, ‘Riviera,’ ‘Tifsport,’ and Tifway bermudagrass as well as Meyer and Diamond zoysiagrass had the best ball lie in unmown (five days after mowing) conditions, while Palisades zoysiagrass had the poorest ball lie in unmown conditions. Ball lie was similar for all cultivars immediately following mowing. These studies identified cultivars of bermudagrass and zoysiagrass that have improved clipping yields, scalping tendencies, and golf ball lie. Introduction Bermudagrass (Cynodon spp.) and zoysiagrass (Zoysia spp.) are the predominant turfgrass species used on golf course fairways and tees in Arkansas (30). Across the transition zone and southern United States, bermudagrass is the most commonly used turfgrass on fairways and tees (24), and bermudagrass and zoysiagrass are adapted to the transition and warm humid, climatic zones (4). Bermudagrass and zoysiagrass are desirable species for golf course fairways and tees due to their deep rooting, disease resistance, recovery potential, drought, heat, wear, traffic, and low mowing height tolerance (3,38,39,40). Several studies have reported differences of growth rate between bermudagrass and zoysiagrass. Patton et al. (31) determined that bermudagrass was faster to establish from seed than zoysiagrass. Volterrani et al. (41) and Busey and Myers (9) reported a faster vegetative establishment for bermudagrasses than zoysiagrasses. Trappe et al. (39) reported both similarities and differences in divot recovery for various bermudagrass and zoysiagrass cultivars. Several important aspects of golf course management can be influenced by growth rate, including clipping yield, scalping tendency, and golf ball lie (6,11,16). Differences in growth rate have been reported between bermudagrass and zoysiagrass (6,13,14). Beard et al. (6) reported variations in leaf extension rates among bermudagrass genotypes, and concluded that this variation would 30 June 2011 Applied Turfgrass Science require adjustment of mowing frequency between cultivars. Although some reports (6,13,14) document differences in leaf extension rates of species or cultivars, other work (21) shows little difference among species or cultivars. Kim and Beard (21) investigated the vertical leaf extension rate of ‘Arizona Common’ bermudagrass, Tifway bermudagrass, and Meyer zoysiagrass in the greenhouse and reported no differences among these cultivars. However, more research is needed comparing clipping yields for commonly used cultivars of bermudagrass and zoysiagrass. Species or cultivars that require less maintenance, such as reduced mowing frequency, are becoming more desirable to turfgrass managers (33). Research documenting differences in clipping yield among cultivars and species would allow superintendents to choose a cultivar that could facilitate a reduced frequency for mowing and possibly reduced use of plant growth regulators. These cultivars could help to reduce equipment wear, labor, and fuel costs associated with maintaining golf course fairways and tees or sports fields. Scalping has been defined as “the removal of an excessive quantity of green shoots from a turf at any one mowing that results in a stubby, brown appearance due to the exposed stems, stolons, and dead lower leaves” (5). While Beard and Beard (5) cite the aesthetic damage scalping incurs on a turfgrass sward, it can also affect plant health (1,8,29,34). Faster growth rates of some species and cultivars increase thatch production, which could promote scalping (11). In addition to excessive thatch accumulation, other potential causes of scalping may include mower adjustment errors, infrequent mowing, or an uneven soil surface (10). In general, scalping also disrupts a consistent playing surface that is necessary for golfing. Differences in bermudagrass and zoysiagrass cultivar susceptibility to scalping have been reported. Across two locations rating for bermudagrass scalping tendency, Patriot was rated to be the most susceptible to scalping, with ‘Princess 77’ and Tifway having moderate scalping damage and Riviera and Tifsport as having minimal scalping (28). In a separate study evaluating scalping tendency of zoysiagrass cultivars in California, ‘Zenith’ was more susceptible to scalping than El Toro, Meyer, and ‘Zorro’ in May and June but similar in scalping tendency in other months (27). Hale (15) reported that ‘Royal’ and ‘Cavalier’ zoysiagrass were more prone to scalping under higher rates of N (≥ 192 kg/ha/year). These works evaluated scalping tendency within species. However, little research has evaluated scalping tendency among multiple species. The position at which a golf ball comes to rest in a turf canopy influences how a golfer will attempt their next shot. A golf ball that rests on top of the canopy provides golfers increased control over golf shots (23). Beard (4) cited turfgrass species, cultivar, and shoot density as determining factors for ball lie. Others have also stated zoysiagrass provides a good golf ball lie for players to take their shot (7,17). Researchers at the University of Arkansas recently developed a method to measure golf ball lie using digital image analysis (36). Little differences among cultivars of bermudagrass and zoysiagrass were reported for plots mown at 1.25 cm, but some differences in golf ball lie were observed for plots mown at 2.5 cm (36). Other work has evaluated the specific management practices that affect ball lie in bermudagrass (16,25), but none have attempted to quantify differences in ball lie among bermudagrass and zoysiagrass cultivars. There are few reports comparing commonly used cultivars of bermudagrass to commonly used cultivars of zoysiagrass and a need exists to evaluate cultivars across species in direct comparison experiments. The objectives of this research were to: (i) quantify clipping yield; (ii) identify scalping tendency; and (iii) quantify golf ball lie for several bermudagrass and zoysiagrass cultivars commonly used on golf course fairways and tees. Evaluating Clipping Yield, Scalping Tendency, and Golf Ball Lie This experiment was conducted at the Arkansas Agricultural Research and Extension Center, in Fayetteville, AR (36°06’N, 94°10’W, 384 m). The planting site was fumigated with methyl bromide at 549 kg/ha on 17 April 2007 and was 30 June 2011 Applied Turfgrass Science a Captina silt-loam soil (fine-silty mixed mesic Typic Fragiudalt) with a pH of 6.6, 1% organic matter, 105 kg P/ha, and 97 kg K/ha. Five cultivars of bermudagrass and seven cultivars of zoysiagrass were used in the experiment (Table 1). Cultivar selection was based on use and availability in the transition zone and southern United States. All cultivars were established as sod in July 2007 as 1.8-m by 1.8-m plots with a 0.3-m border maintained to prevent contamination from adjacent plots. Due to limited sod availability, ‘Diamond’ zoysiagrass was initially planted as 0.5-m by 0.5-m plots until additional plant material could be propagated. Diamond plugs were planted in May 2008 in the remainder of the plot area and plots were fully established by August 2008. Table 1. Cultivars, experimental notation, and species of bermudagrass and zoysiagrass used in this study. * The cultivars Princess 77 bermudagrass and Zorro zoysiagrass were each evaluated using two experimental notations before the cultivars were released for commercial use. Cultivar Experimental notation Species Cavalier DALZ8507 Zoysia matrella (L.) Merr. Diamond DALZ8502 Zoysia matrella (L.) Merr. El Toro UCR#1 Zoysia japonica Steud. Meyer Z-52 Zoysia japonica Steud. Palisades DALZ8514 Zoysia japonica Steud. Patriot PKC 18-4 Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy Princess 77 FMC-77, SWI-77* Cynodon dactylon (L.) Pers. var. dactylon Riviera OKS 95-1 Cynodon dactylon (L.) Pers. var. dactylon Tifsport Tift 94 Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy Tifway Tifton 419 Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy Zenith ZNW-1 Zoysia japonica Steud. Zorro DALZ8510, DALZ9601* Zoysia matrella (L.) Merr. All experimental areas were maintained under typical golf course fairway conditions, with a mowing height of 1.3 cm. All plots were fertilized with nitrogen using urea (46-0-0) at 24 kg/ha per growing month for zoysiagrass and 49 kg/ha per growing month for bermudagrass based on input from Arkansas golf course superintendents. The experimental design was a randomized complete block design with four replications. Clipping yield was measured on 4 and 28 August and 23 September 2008 as well as on 4 June, 13 July, and 31 August 2009. The area of each plot from where clippings were collected was measured prior to each collection and recorded to provide a total dry weight per unit area measurement. A Jacobsen Greensking (Textron Co., Charlotte, NC) mower was used to collect clippings and two passes (opposite directions) were made on the same area of the plot to ensure complete clipping collection. Clippings were collected when all plots grew to a height of at least 1.9 cm, w

Moderate Salinity Does Not Affect Germination of Several Cool‐ and Warm‐Season Turfgrasses

Germination of warm- and cool-season turfgrasses was assessed at salinity levels commonly found in recycled irrigation water. Cool-season grass seeds included in the study were Thermal Blue hybrid bluegrass [Poa arachnifera (Torr.) x pratensis (L.)]; Barlexas II, Southeast, and Tar Heel II tall fescue [Festuca arundinacea (Schreb.)]; Brightstar SLT and Catalina perennial ryegrass [Lolium perenne (L.)]; Salty and Fults alkaligrass [Puccinellia distans (Jacq.)]; and Dawson red fescue [Festuca rubra trichophylla (L.)]. Warm-season grass seeds used in the study were bermudagrass Numex Sahara, Princess 77, and Transcontinental [Cynodon dactylon (L.)]; Companion zoysiagrass [Zoysia japonica (Steud)]; and Seaspray seashore paspalum [Paspalum vaginatum (Swartz)]. Each grass was incubated at salinity levels from 0.6 to3.0 dS/m. Germination was considered successful upon radicle emergence and the first leaf growing past the coleoptile. Despite species and cultivar variation in germination success, germination was not inhibited in any of the tested cultivars at the salinity levels used in this study, suggesting that germination may not be the most salt-sensitive stage in turfgrass development.

Turfgrass Winterkill Observations from the Transition Zone

T HE winter of 2013–2014 will be remembered by many turfgrass managers in the transition zone as one of the most severe and devastating in the past two decades. Although we experienced a similar winter in 2000–2001, we have only seen mild examples of winter injury since that period. Extended low temperatures were common throughout the 2013–2014 winter (Fig. 1) and the region experienced several prolonged periods where single digit low temperatures occurred for three or four consecutive days. Although there was variable precipitation throughout the region (Fig. 1), it was not an excessively dry winter, which suggests that most of the injury observed in the region was likely the result of direct low temperature kill rather than desiccation-related problems. he winter injury observed in the transition zone extended from golf courses to athletic ields and home lawns and included damage to bermudagrass (Cyndon spp.), St. Augustinegrass (Stenotaphrum secundatum), and even zoysiagrass (Zoysia spp.). In the research plots at Fayetteville, AR, the principal story regarding survival against low temperature remains improved genetics. he new National Turfgrass Evaluation Program (NTEP) bermudagrass and zoysiagrass trials were planted in Fayetteville in early July 2013 and many cultivars and experimental varieties experienced moderate to signiicant winter injury (Fig. 2). Equally, there were many cultivars that survived the winter without problems. A full reporting of the data from those trials will be available through NTEP in the early part of 2015, but some of the commerciallyavailable bermudagrass cultivars that had the greatest winter survival included Northshore SLT, Latitude 36, Astro, Riviera, and Patriot. In the zoysiagrass trial, cultivars with good survival included Zeon, Empire, Meyer, and Cavalier. As has been documented in the past, warm-season grasses are most susceptible to winter injury in the irst year of planting (Richardson et al., 2004), so some of the injury observed in the research trials may have been partially due to the late plantings in 2013. Published in Applied Turfgrass Science DOI 10.2134/ATS-2014-0049-BR