Best Practices for Maintaining Bentgrass Greens in a Hot Climate.
The following fourteen items are critical for managing creeping bentgrass putting greens.
Heat and Drough Tolerance Reported on Three Year Old 007 Greens in Texas
Nothing means more to a golf course superintendent than long term performance after seeding a new bentgrass varieity. Performance proven in the field, on his own golf course, and under extreme weather conditions.
Nathan Neumann, Golf Course Superintendent, Wichita Falls Country Club, Wichita Falls, Texas has reported, "We have quite a summer going so far (2011). We had the hottest June ever here, avg. temps were 104 F and averaged 75 F for the month (June 2011). We have had 45 days over 100 F so far this year and counting. July is continuing the hot and dry trend. We are still in a severe drought and the golf course we will be on water restrictions possibly as soon as next week."
"Overall, the 007 greens are doing well considering the heat. We are hand watering every day, not using any overheads just trying to manage moisture. They were ¼” aerified last week (early July) and deep watered. I raised my HOC slightly to 0.130 since we do not have any events for the remainder of the summer, but still achieving good speeds at this height. I am still light verticutting and topdressing. Weekly foliar feeding and on a two week preventative fungicide schedule."
Photo below of a 007 green taken early July, 2011, Wichita Falls CC, after a month of extreme heat and drought. Photo credit: Nathan Neumann, Golf Course Superintendent, Wichita Falls Country Club, Wichita Falls, Texas.
The photo below is a close up of the green above. Note the fine leaves and uniform density of a mature, three year old 007 green. Photo credit: Nathan Neumann, Golf Course Superintendent, Wichita Falls Country Club, Wichita Falls, Texas.
Bentgrass Summer Stress from the Summer of 2010 and Reports of Bacterial Wilt on Putting Greens.
The following report was written by Dr. Leah Brilman, edited by Richard Hurley
In the USGA Green Section Record, newspapers and on Internet sites the talk has been the summer heat and how it has influenced creeping bentgrass and Poa annua greens.
When all five of the following factors occur at the same time cool season grasses can no longer maintain their basic frunctions.
Records were set across the United States and into Europe for number of days above 90 and 100 degrees F, number of days with low temperatures above 70 degrees F, days with an average dew point above 70, days when the average wind speed was 10 mph or less and days when the average soil temperature has been above 86 degrees F.
Turfgrass breeders have been working for 30 years to improve heat and summer stress resistance of creeping bentgrass.
Breeders have collected new bentgrass germplasm from putting greens growing in high stress environments. The turf breeder then evaluates the new germplasm under low mow stress conditions as part of the selection process. Significant progress has been made in bentgrass stress resistance but also new challenges have arisen as mowing heights have been reduced.
Other factors that can contribute to struggling bentgrass include reduced aerification, use of certain herbicides and fungicides, reduced fertility levels and even growth regulators. Poa annua is even more prone to problems than creeping bentgrass.
High soil temperature is the most critical factor in decline of bentgrass and other cool season grasses during the summer.
Multiple studies have shown that high soil temperatures, whether the air temperature is low or high, is detrimental to root growth. Research by Dr. Bingru Huang, Rutgers University, showed a decrease in soil temperature from 95 degrees F to 90 degrees F at 0.125 to 0.157 inch mowing height maintained acceptable turf quality for L-93 and higher turf quality for Penncross over 21 days.
Significant increases in tiller density, clipping yield and root number were observed when soil temperatures were reduced from 95 to 85 degrees F.
Cooling the soil at night was more effective than daytime cooling in maintaining turf quality. At high soil temperatures plant respiration increases and uses up the energy reserves of the plant stored in the roots and crowns.
Young bentgrass greens may suffer more since they are more upright, have less leaf surface and less extensive crowns and stolons so less reserves.
One of the most serious signs of extreme stress on creeping bentgrass were the many reports of bacterial wilt on multiple cultivars of bentgrass, including Penn A-1, Penn G-2, Penn A-4, L-93, and Tyee.
Most University trained turfgrass pathologists now think Bacterial wilt was a secondary pathogen that moved into a weakened plant.
One of the best clues that this is a secondary pathogen was a report by the USGA of greens that did not have wilt where fans were cooling the surface and wilt was present on the rest of the green. Another example is the variety Tyee suffered from bacterial wilt on greens in Texas where the airflow was poor after heavy rains but the Tyee nursery from the same course was in good condition and was used to resod the damaged greens.
Dr. Richard Latin of Purdue stated “that most reports seem to involve a few cultivars Penn A-4, L-93) that are more intensively managed. The likelihood that these varieties have a genetic susceptibility to infection or invasion by these bacteria is low.” The intensive management under extreme conditions can put further stress on the plants. Fans and fan placement seem to be critical to bentgrass survival.
During the summer of 2010 on the Turf Disease Blog (www.turfdiseases.blogspot.com or the Turf disease Facebook page) turf pathologists came up with the equation, No Wind + Heat = Dead Grass.
Fans and syringiing have been documented to be the best solutions for bentgrass summer stress, in addition to cutting height and other management changes. Guertal and Han (2002, 2006, 2009) did a series of studies on using fans, syringing and irrigation to reduce the soil temperature of creeping bentgrass during the summer in Alabama. During the first part of the summer fans during the day reduced soil temperature but during the hottest time it was beneficial to run the fans 24 hrs / day. Syringing or irrigation provided added benefit to using fans but were not as effective as fans alone. If no fans were used morning irrigation cooled the roots better than afternoon irrigation.
Observations have shown fans are most beneficial if used in the direction of the prevailing wind and are helped by thinning brush or trees, especially to optimize this flow. It is critical to have sun in the mornings under these conditions since this is the time of day photosynthesis may occur.
The second equation the turf pathologists had was Rain + Heat = Dead Grass.
Rain has the same effect as overirrigation which can lead to scald or wet wilt. Scald occurs when you have standing water or overly wet thatch with sunny, hot weather. The water rapidly heats up and stays hot and the plant dies, with oxygen depletion playing a role. The death of roots in the summer increases the retention of water in this organic layer. Wet wilt occurs when the roots, often already reduced due to heat, cannot absorb enough water, even though water is present, for the transpiration of water used for cooling, the stomates close raising the internal plant temperature and the plant dies.
Management Recommendations for Bentgrass Greens Growing in a Hot Climate