Photo: Pete Landschoot, Penn State
Currently, over 50 bentgrass cultivars are commercially available in the U.S., and many differ with respect to rate of establishment, density, color, disease resistance, stress tolerance, and aggressiveness. If you are a golf course manager considering resurfacing one or more fairways or tees, or just interseeding thinning areas, know that there are some excellent bentgrass cultivars from which to choose.
Finding reliable information on fairway and tee bentgrasses can be challenging. If you seek advice from seed company reps, consultants, or other turf managers, be sure to consider that soil types, microclimates, golfer expectations, and resources for managing turf at your course are unique, and may differ from those of other golf courses. Also, take into account that some bentgrass cultivars are more suitable for putting greens than for tees and fairways. Some special considerations for fairways and tees are rate of thatch accumulation, tolerance to diseases, and ability to resist Poa annua encroachment.
One source of information you can use in the bentgrass selection process is test data from the National Turfgrass Evaluation Program (NTEP). NTEP is an organization that coordinates tests of commercial and experimental turfgrass cultivars at universities throughout the U.S. Data generated from these tests can provide comparative information about turfgrass characteristics and performance. Although NTEP tests can't simulate all the traffic and management conditions found on golf courses, they do provide information on seedling vigor, quality, density, color, disease and insect tolerance, and other parameters.
NTEP Bentgrass Putting Fairway/Tee Test
In September of 2008, 23 bentgrass cultivars and selections were established from seed at the Joseph Valentine Turfgrass Research Center in University Park, PA, as part of a five-year NTEP test. Entries were supplied to NTEP by private seed companies and were seeded at 1.1 lbs seed/1000 ft2 in plots on a tilled Hagerstown Silt Loam soil. Three replicate plots of each entry were included in this test and plots were randomized in each rep. The test was mowed three times per week at 0.5 inch during the growing season, core aerated once per year, and received between 2 and 3 lbs nitrogen/1000 ft2 per year for most of the five-year test. Assessments of bentgrass performance were made by the author, and are based on visual ratings using a 1-9 scale, with 9 indicating best performance for a particular criterion. Performance criteria, including seedling vigor, quality, color, and disease incidence were used to evaluate the bentgrasses. Monthly quality ratings are a measure of density, texture, uniformity, and lack of disease. P. annua encroachment ratings were made at the end of the test, and were assessed as a percentage of P. annua cover in each plot.
The 2008-2013 NTEP Fairway/Tee Test site at the Joseph Valentine Turfgrass Research Center in University Park. Photo: Pete Landchoot, Penn State
Summary of Results
Data for performance assessment ratings are presented in Tables 1 and 2. All cultivars listed in these tables are commercially available except for SRP-1WM, A08-EBM, BCD, A08-FT12, and PST-R9D7.
Of the commercially available cultivars in this test, 007, Authority, Proclamation, Pure Select, Barracuda, Pin-Up, Declaration, and Luminary tended to receive the highest average quality ratings from 2009-2013 (Table 1). These cultivars (all creeping bentgrasses) ranked higher than other entries due to their excellent density, fine texture, uniformity, disease resistance, and low amounts of P. annua. T-1, Benchmark DSR, and CY-2 creeping bentgrass cultivars received high-quality ratings during the first three years of the test period, but slightly lower ratings in the last two years. Crystal Bluelinks, L-93, and CY-2 received intermediate quality ratings throughout most of the test period; whereas, Penncross and Princeville ranked lowest in quality among the creeping bentgrasses (in large part due to their lower density and coarser texture).
Plots of bentgrass showing good density, texture, color, and uniformity. Photo: Pete Landchoot, Penn State
Of the six colonial bentgrass cultivars evaluated in the 2008-2013 NTEP Fairway/Tee Test, only Greentime and Tiger II are commercially available. Both of these cultivars received high to medium quality ratings during the first year of the test, but quality steadily declined over the next four years. The main reason for the decline in quality was colonization of plots with P. annua.
Seedling vigor, an estimate of ground cover and plant height during the early stages of seedling establishment, was evaluated for all cultivars shortly after seeding in September of 2008. Seedling vigor ratings were highest for Penncross, Princeville, T-1, Proclamation, Barracuda, and Benchmark DSR; however, thirteen other cultivars and selections had seedling vigor ratings very close to these six cultivars (Table 2). Commercial cultivars that were slowest to establish in this test were Greentime, Memorial, and Pin-Up. By late October, all of the plots in this test showed complete turf cover and were able to tolerate weekly mowing.
Table 1. Quality ratings for the 2008-2013 National Turfgrass Evaluation Program Bentgrass Fairway/Tee Test at Penn State. Data represent averages of monthly quality ratings for each year of the 5-year test. Quality is rated on a scale of 9 to 1, with 9 = highest quality.
Quality Rating Averaged Over Growing Season§
|Entry||Bentgrass Species||2009||2010||2011||2012||2013||Five-year Ave.|
§Quality ratings indicate the overall appearance of the turf and can incorporate several components including density; texture; uniformity; as well as freedom from disease, weed, and insect damage. Quality is rated using a scale of 1 to 9, where 9 = highest quality.
*Indicates cultivar is commercially available.
ǂLSD = Least significant difference. Differences between two entries are statistically significant only if the LSD value, listed at the bottom of each column, is exceeded by the numerical difference between the two entries. For example, if cultivar 'A' is 1.0 unit higher in quality than cultivar 'B', then this difference is significant only if the LSD value is less than 1.0.
Table 2. Seedling vigor, genetic color, dollar spot, and P. annua ratings for the 2008-2013 National Turfgrass Evaluation Bentgrass Fairway/Tee Test. Ratings are based on a scale of 9 to 1, with 9 = fastest establishment for seedling vigor, darkest green genetic color, and no dollar spot present. Poa annua encroachment ratings are based on a percent (%) P. annua cover basis.
|Entry||Bentgrass Species||Seedling Vigor§||Genetic Color§||Dollar Spot Tolerance§||% P. annua Encroachment§|
§Numerical ratings indicate seedling vigor (estimate of ground cover and plant height during the early stages of seedling establishment), where 9 = greatest ground cover and plant height and 1 = very sparse cover and slow growth); genetic color (9 = darkest green color and 1 = yellow-green turf); tolerance to dollar spot (9 = no disease present and 1 = extensive disease symptoms and turf damage); and percent P. annua encroachment in plots at the end of the test period (0 = no P. annua cover and 100 = complete P. annua cover).
*Indicates cultivar is commercially available.
ǂLSD = Least significant difference. Differences between two entries are statistically significant only if the LSD value, listed at the bottom of each column, is exceeded by the numerical difference between two entries. For example, if cultivar 'A' is 1.0 unit higher in quality than cultivar 'B', then this difference is only significant if the LSD value is less than 1.0.
Bentgrass genetic color
Although genetic color of a cultivar does not influence the playability of bentgrass, it can make a difference in the aesthetic appeal of fairways and tees. The color of bentgrasses can be important in maintaining stand uniformity when blending two or more cultivars. Bentgrasses tend to segregate after a few seasons, and a dark-green cultivar blended with a light-green cultivar may lead to a patchy appearance of fairways and tees.
Genetic color ratings show that T-1 creeping bentgrass had the darkest green color of all entries in the 2009-2013 Bentgrass Fairway/Tee Test, closely followed by Benchmark DSR (Table 2). The majority of commercial creeping bentgrasses exhibited a medium- to light-green color, with color rating values ranging from 6.6 for Luminary to 4.7 for Princeville. The commercial colonial bentgrasses (Tiger II and Greentime) produced a yellow-green hue that appeared lighter green than the creeping bentgrasses. Although most people tend to favor dark-green over-light green turf, the yellow-green hue of P. annua tends to stand out more in darker-green bentgrass stands.
Dollar spot tolerance
Bentgrass cultivars differed in their susceptibility to dollar spot disease in this test. Most commercial creeping bentgrasses (Declaration, Proclamation, Benchmark DSR, Barracuda, 007, Pin-Up, Luminary, CY-2, L-93, and Memorial) and both commercial colonial bentgrasses (Tiger II and Greentime) showed very good tolerance to dollar spot during the 2008-2013 test period (Table 2). Authority, Pure Select, and Crystal Bluelinks showed intermediate tolerance to dollar spot; whereas, the least tolerant commercial cultivars were T-1, Penncross, and Princeville.
Bentgrass cultivars showing differences in dollar spot susceptibility. Photo: Pete Landchoot, Penn State
P. annua encroachment
An important fairway/tee management strategy for golf course superintendents is the use of bentgrass cultivars that are aggressive enough to compete with P. annua. P. annua began to move into the 2008-2013 NTEP Fairway/Tee Test two years after establishment, and by 2013 plots of some cultivars were more heavily infested than others. Commercial cultivars with the least amount of P. annua included Pin-Up, 007, Benchmark DSR, Barracuda, Declaration, Proclamation, Pure Select, CY-2, T-1, Luminary, and Authority. The greatest percentage of P. annua was detected in plots of Princeville, Tiger II, and Penncross.
Differences in P. annua contamination in bentgrass plots. Plot on the left in foreground is Pin-Up creeping bentgrass and plot on right is Greentime colonial bentgrass. Photo: Pete Landchoot, Penn State
As stated earlier in this article, some bentgrass cultivars are better suited for putting greens than for tees and fairways. Cultivars with extremely high tiller densities can become "puffy" due to rapid thatch build-up when grown in fairways and tees. This can result in scalping and other poor mowing characteristics. Although thatch measurements were not collected at the University Park site, we did observed some scalping damage on Declaration, Proclamation, Benchmark DSR, and Pin-Up on one occasion during a warm, rainy period in 2013 (data available at ntep.org). When using high-density cultivars for fairways and tees, be sure to monitor thatch levels and make provisions for verticutting and core aeration for thatch reduction.
Scalping damage on tee planted to a high-density cultivar of creeping bentgrass. Photo: Pete Landchoot, Penn State
One of the limitations to the use of colonial bentgrasses for fairways and tees in the Mid-Atlantic region of the U.S. is its susceptibility to brown patch disease. Although no brown patch data were collected at the University Park site, ratings from the New Jersey NTEP site indicated that colonial bentgrass entries ranked lower than most creeping bentgrasses with respect to tolerance to brown patch (see ntep.org).
The results of the 2008-2013 test of fairway/tee bentgrasses reflect the response of cultivars to the management regime imposed at this site and environmental conditions in University Park. Several commercial bentgrass cultivars used on golf courses in the U.S. were not included in this test. Some of these cultivars were evaluated in previous NTEP tests and data from these tests can be found on the NTEP website (ntep.org). A new NTEP bentgrass fairway/tee test was initiated in 2014 and contains some new commercial cultivars and experimental selections. Hopefully, this test will reveal continued improvement of bentgrasses for golf courses in the Mid-Atlantic region.