Promising turf for cool, humid regions

Dr. Cale Bigelow operates a Stimpmeter to test golf ball roll speed.

A lot has changed in turfgrasses since the early days of golf in the United States, and, as in many situations, the only constant is change. Recent research results are encouraging turfgrass managers to take closer looks at new cultivars that may offer better turfgrass in specific locations. Recent turfgrass trials at Purdue University, West Lafayette, Ind., are particularly important for the cool, humid region.

In early golf course construction, putting greens were often planted with a mixture known as South German bentgrass, which contained creeping, colonial and velvet bentgrass. Bentgrass greens gained popularity, but early bentgrasses often had a patchy appearance. Greens were later established using stolons, which resulted in a more uniform appearance, but less genetic diversity, making the turf sometimes more susceptible to certain pests.

Turfgrass researchers are continually looking for ways to improve turfgrasses for use in every setting. Dr. Cale Bigelow, Purdue turfgrass researcher, said “Recent bentgrass trials across the United States in conjunction with the National Turfgrass Evaluation Program (NTEP), including a trial located at Purdue University, indicate that advances in turfgrass breeding have produced new cultivars that should be considered for use in the cool, humid region.”

In recent cultivar trials, Bigelow has examined the advantages of newer cultivars in the cool, humid climate found in the Midwest. While the trials included a variety of cultivars, the emphasis was on the best performing bentgrass cultivars for the region. Considerations included best appearance, least disease, highest shoot density and most consistent seasonal shoot density, along with best spring green-up and fall color retention.

Bigelow draws on his experiences as an assistant golf course manager at Belle Haven Country Club and at Robert Trent Jones Golf Club, both located in suburban, Washington, D.C. His research program at Purdue focuses on helping turf managers grow the highest quality turfgrass, while using the fewest management inputs. He cited the increased importance of cultivar selection for particular regions, especially as inputs are reduced.

Bigelow said, “If turfgrass performance, such as increased dollar spot incidence or poor tolerance to low mowing, has been a recent issue, a renovation to a newer cultivar may be a consideration. Many managers are mowing lower and tighter than ever before, and are using fewer pesticides and less fertility. Reluctance frequently exists among turf managers to try the newer cultivars. Nobody seems to want to be the guinea pig.”

Looking back

Stolons had a short shelf life and were difficult to handle and plant, spurring interest in the development of improved seeded bentgrasses. Bigelow noted, “One early cultivar was Seaside, which formed a grainy turf also prone to severe segregation. Breeding improvement programs continued, and Penncross was released in the mid-1950s. This cultivar had a rather wide genetic base, formed a high-quality, persistent turf adapted to many climactic regions. It, too, was somewhat prone to segregation.”

Further improvements were made with Penneagle released in the 1970s, followed by Pennlinks, Providence and others in the 1980s. Many other cultivars followed that offered excellent turf, both in appearance and performance, and golf course construction boomed across the country in the 1980s and 1990s. Today, creeping bentgrass is the most commonly used turfgrass on high-end golf course tees, fairways and putting greens throughout the cool, humid climate.

Differences in dollar spot are illustrated on trial plots.

With increased playing expectations, traditional Kentucky bluegrass courses were sometimes changed over to bentgrass. The new millennium has brought a move toward managing turfgrass on sites from home lawns to golf courses in a more ecologically balanced manner. Concerns about chemicals in runoff, water availability and higher costs are dictating fewer fertilizer and irrigation inputs. At the same time, as playing expectations have continued to increase, golf course managers are often pressured to deliver turf with higher performance, sometimes presenting new management challenges.

Bigelow pointed out, “As these new management challenges increase, more emphasis must be placed on the particular growing environments in which turf must perform, and finding plant species and cultivars with the correct traits adapted to those growing environments.”

He said, “During the past 20 years, golfers have expected and demanded the firmest, smoothest putting surfaces. Golf course managers have responded by modifying their management practices.” According to Bigelow, consistent fast ball speeds have become the general expectation on many courses, and mowing heights have been reduced with the industry standard now no more than 1/8 inch.

“Many golf courses in the past 15 years that have hosted U.S. Opens, PGA Championships and PGA Tour events have renovated to newer cultivars, which have required greater maintenance intensity,” Bigelow said.

“Diseases like dollar spot are reported to be a serious challenge,” Bigelow said. “Many turf managers recommend A-4 or A-1/A-4 blend for new putting greens, sometimes because the managers are comfortable with its track record. As turfgrass scientists, we are consistently striving to improve conditions and provide solutions to management challenges.”

Looking for answers

With a goal of finding practical solutions to some of the new challenges turfgrass managers face, Purdue conducted trials that included 29 cultivars, both those commonly planted and newer, experimental cultivars.

Bigelow evaluated the trials for three consecutive years. “The data breaks the cultivars into three tiers,” he said. The first tier included 10 cultivars with excellent performance. The second tier included 13 cultivars that performed well, but did not qualify as “best of the best,” according to Bigelow. The third group of cultivars included six commonly planted cultivars. Bigelow said, “This trial is excellent to observe genetic improvement.”

Trials included not only cultivars from Purdue’s NTEP participation, but also other industry standards. The bentgrasses were established on a clay-based native soil push-up research putting green. Approximately 3 inches of sand topdressing had accumulated. The trial location receives full sun and was given about 3 pounds of nitrogen per 1,000 square feet each year. Irrigation supplemented rainfall, and it was mowed at .140 inch with a triplex, core aerated twice annually with moderate sand topdressing applied twice during active growth.

Tier breakdowns

The first tier cultivars included Benchmark, Declaration, Kingpin, Penn A1, Authority, 007, Memorial, T-1, MacKenzie and an experimental IS-AP9. Bigelow noted that all 10 cultivars showed consistently high overall appearance. He attributed this appearance to high shoot density, fine leaf texture and consistent seasonal color along with good to excellent dollar spot resistance. “Eight of the 10 cultivars are relatively new to the market,” he said.

The second tier included 13 cultivars that performed well, but were not in the category of the “best of the best.”

The third tier included a group of cultivars that performed poorly in comparison with the best. Many commonly planted cultivars, including Penncross, Providence, Pennlinks, Pennlinks II, Backspin and Crenshaw, were included in this group. Bigelow noted that these had coarser leaves, less shoot density or a loss of summer shoot density. Additionally, they were very prone to dollar spot. While he noted that these cultivars perform adequately on courses with lower expectations, better cultivars are available and should be considered for the cool, humid region.

Increased stress on turfgrass

Bigelow noted that a number of courses were planted in Crenshaw for its heat tolerance. It has been frequently planted in the Southeast and some parts of the mid-Atlantic region. However, it is one of the least resistant to dollar spot, thereby making preventive fungicide sprays necessary. It also greens up rather slowly in the spring in more northern locations. “This is a good example of how a good cultivar can present new management challenges,” Bigelow said. “Perhaps it was simply planted in the wrong growing environment, a humid one rather than an arid one, such as the area in which it was bred. These challenges should be kept in mind as new bentgrass generations are considered.”

The higher expectations have continually increased stress to the turfgrass from the lower mowing heights and reduced irrigation and fertilizer use. These reduced inputs are expected to continue to be a major focus, while high expectations are likely to continue as well.

Looking to the future

Bigelow noted that turf managers are often reluctant to plant new cultivars because of higher maintenance requirements. He emphasized that advances in turfgrass breeding, however, make these newer cultivars better choices for many courses with high expectations, and that the recent trials indicate strong advantages of some of these newer cultivars for use in the cool, humid region.

He said, “It has been more than 10 years since the As and Gs were released, and breeders have developed grasses with better pest and environmental stress resistance. If golf course managers are faced with future renovations and are uncertain about which cultivar to plant, they try some of these new cultivars on a practice green or chipping area. They should watch how these new cultivars respond to specific management programs in individual microclimates. This on-site information can be valuable, and also allows those making the financial decisions input as well. Researchers  are always happy to help set up these evaluations.”

Nancy Riggs is a freelance writer and frequent contributor to Turf. She resides in Mt. Zion, Ill.