By Brian Whitlark, agronomist, Southwest RegionJuly 20, 2011
A combination of low overnight temperatures, extended periods where the mercury did not rise above freezing, aggressive overseeding preparation and winter desiccation, all contributed to poor bermudagrass recovery from overseeding in southern Arizona.
Transition from overseeded cool season grasses, such as poa trivialis, bentgrass and fine fescues to bermudagrass, has historically been fairly seamless on putting surfaces in the Southwest. That is, until this year. Roughly 20% of golf courses are experiencing transition woes this summer on greens. Historically, that number is less than 5%. That being the case, why did courses see such problems with putting green transition this year?
Greens that experienced the weakest bermudagrass recovery are likely suffering due to a combination of factors, including one or more of the following:
- Overseeded greens that were aggressively prepared for seeding. There has been a trend in preparing for overseeding with less aggressive methods, but some turf managers are forced to conduct thatch and organic matter reduction tactics at overseeding time, which will diminish bermudagrass recovery the following spring.
- In localized areas, especially in Tucson, winter temperatures dipped down to 10° F, and experienced three to four days without exceeding the freezing mark. This cold snap, when combined with additional stresses, likely led to poor transition.
- There has been a slight trend to increase overseeding rates to unimaginable levels. In some cases, more than 30 lbs of Poa trivialis has been applied per 1,000 ft2. At least one turf manager is confident (and willing to admit) that such a high density of Poa trivialis plants led to poor bermudagrass recovery.
- Winter desiccation likely played a large role in many weak areas, especially on slopes and mounds. When freezing temperatures may be an everyday occurrence, it is common to withhold irrigation in an effort to avoid frost.
Although turf managers are unable to control the weather, they should consider incorporating the following strategies to minimize transition problems in the future:
- Aggressively verticut and aerate bermudagrass greens in July and August in the desert southwest. Use only light surface disruption prior to overseeding. Late season thatch and organic matter reduction tactics are ill-advised.
- If using Poa trivialis, seed at 6-13 lbs 1,000 ft2. One course in the north Scottsdale area seeds with 6 lbs. of Poa trivialis each year and offers some of the best putting surfaces in the region.
- Consider experimenting with a growth regulator such as Embark to strategically shift the competitive edge to the underlying bermudagrass (read and follow label directions).
- Beginning in February, begin surface grooming, brushing and verticutting to thin the overseeded turf. Progressively get more aggressive as heat units accumulate.
- Use soil moisture sensors and/or frequent soil coring to avoid winter desiccation problems. Although the overseeded turf may not show signs of stress, the soil may be too dry to sustain bermudagrass health.
- Consider purchasing greens covers (http://turf.lib.msu.edu/2000s/2007/071101.pdf), (https://www306.livemeeting.com/cc/usga/view?id=J2T2T7) and roll them out when temperatures are expected to dip below 25°F at night and remain at or slightly above freezing for several days.
- Lastly, course officials should strongly consider eliminating overseeding from the ultradwarf greens program. All of the bermudagrass greens that experienced transition woes this year were overseeded. Furthermore, courses that have made the choice to not overseed greens, enjoyed smooth, fast putting surfaces in October, when overseeded greens are often wet and slow. A growing number of courses are blazing the trail in the Southwest with continued success.
This update is intended to serve as a wakeup call for course officials, members and turf managers in the desert Southwest, where some may need to consider altering their overseeding plans to avoid the transition woes experienced this summer.
Brian Whitlark is an Agronomist with the Southwest Region of the USGA Green Section located in Gilbert, Arizona.