Newer bermudagrass varieties such as ‘TifTuf’, ‘Tahoma 31’, ‘Latitude 36’, ‘IronCutter’ and two soon-to-be-released cultivars developed by the University of California at Riverside, ‘Presidio’ and ‘Coachella’, offer significant improvements over common varieties and even the gold standard ‘Tifway 419’ which has been used for more than 30 years in southern states. But converting from existing bermudagrass to an improved variety is no easy task. If done hastily, the result will be a hodgepodge of new and existing bermudagrasses that won’t look or perform as hoped.
The USGA is supporting research conducted by Dr. Jim Baird and his team at UC Riverside to examine the best steps, both chemically and mechanically, to convert from old to new bermudagrass. The research is divided into three phases due to the complexity of this problem. At the recent field day hosted by UC Riverside, preliminary results from Phase 1 of this research were on display. Here are the highlights gleaned from the research thus far:
- Treatments began this year on July 20. Plots received either no herbicide applications or anywhere from one to four sequential applications. The plots receiving the fourth and final application were treated on September 21. Sufficient irrigation was supplied throughout the study period.
- Half of the plots also received nitrogen fertilization with granular urea starting one week after the first herbicide application and continuing every two weeks to determine if nitrogen fertilization enhances control. So far there is no evidence that nitrogen improved control.
- While a variety of herbicides were examined, it is clear that glyphosate at 128 ounces per acre is the most important active ingredient.
- Enhanced control was achieved using multiple applications of glyphosate in combination with Fusilade II (fluazifop) at 24 ounces per acre or Turflon Ester Ultra (triclopyr and methylated seed oil) at 32 ounces per acre – or all three mixed together. Segment II (sethoxydim) did not seem to enhance control when added to glyphosate.
- One application is not enough! This research confirms field observations that courses need to plan on more than one herbicide application to achieve acceptable control of the existing bermudagrass. The research so far says that two is better than one, and three is better than two. We will have to wait and see if four applications are better than three. Practically, courses may not be able to make a series of herbicide applications over 10-12 weeks before resurfacing, but the longer the application period the better the control.
- It is critical to wait a minimum of 21 days between herbicide applications, at least in Riverside, California. Spraying at a shorter interval wastes time and money. In some cases, it will be necessary to extend the spray interval to 28-30 days. The key is allowing the existing bermudagrass to regrow – and to see green tissue – before making the next application.
Phase 1 of the study will be completed this fall. Phase 2 is set to begin prior to overseeding and will continue into spring 2024. The primary goal of Phase 2 is studying the impact of introducing glyphosate into the bermudagrass plant at a time when it is mobilizing carbohydrates to its underground rhizomes in preparation for winter. Phase 3 will begin next year and the goal is to evaluate how effective mechanical methods like fraise mowing, asphalt grinding and deep vertical mowing are for bermudagrass control.
A big thanks to Dr. Jim Baird and the entire team at UC Riverside for a fantastic field day. I would also like to bid a bittersweet goodbye to Drs. Marta Pudzianowska and Pawel Orlinski as they move on in their turfgrass research journey to Mississippi State University this fall. Finally, stay tuned for my next regional update on the two new bermudagrass cultivars developed and soon to be released by the UC Riverside turfgrass breeding program.
West Region Agronomists:
Brian Whitlark, regional director – bwhitlark@usga.org
Cory Isom, agronomist – cisom@usga.org