The transition period when overseeded ryegrass succumbs to the hot temperatures and the understory bermudagrass emerges can cause golf course superintendents many sleepless nights. Weather conditions vary significantly from year to year and superintendents have learned that they cannot rely on a natural transition when the ryegrass dies and bermudagrass fills in on its own with the onset of hot temperatures. This strategy often leads to weak and thin bermudagrass cover once the ryegrass is gone. This is partially because as the ryegrass senesces, it forms a black organic mat at the soil surface that discourages the emerging bermudagrass. Some research has also indicated that the senescing ryegrass leaves have an allelopathic effect on the bermudagrass.
Scott Anderson, superintendent at the Encanterra Country Club in Arizona, was all too familiar with the challenges of bermudagrass transition. For years the facility had focused on maintaining green overseeded turf at the expense of the underlying bermudagrass. The bermudagrass recovery in the rough was especially troublesome. Four years ago, Anderson convinced decision-makers at the facility to employ a proactive strategy to shift the competitive advantage from the overseeded ryegrass to the understory bermudagrass in the rough areas. This strategy has paid off with a much more successful bermudagrass transition. Here are the steps deployed by Anderson:
- The rough height of cut is maintained at 1.5 inch following overseeding and through December.
- On January 1, the height is reduced to 1.25 inch.
- The height is reduced to 1 inch during the first week of February. They maintain this height during the primary tournaments and events at the course.
- On April 1, the height is lowered to 0.75 inch.
- On April 8, the height is significantly reduced to 0.35 inch.
- In mid-April, the herbicide penoxsulam is applied at 12 ounces per acre to slowly remove the perennial ryegrass.
- The penoxsulam application also allows Anderson to initiate nitrogen inputs that benefit the bermudagrass without creating undesirable ryegrass growth.
- A combination of spiking, vertical mowing and solid-tine aeration are used routinely beginning in February.
This proactive strategy has improved bermudagrass recovery each year. In the desert southwest, the success of transition is often measured by the amount of bermudagrass sod laid in the summer. Anderson hauled in more than 2 acres of sod in 2015 – for a golf course with 150 acres of turf. Since then, only 11,000 square feet of bermudagrass sod have been needed per year from 2016 through 2018. The sod is placed primarily in high-traffic areas.
Other superintendents have enjoyed similar results. A proactive transition strategy has proven to be the best approach to encourage bermudagrass recovery in all overseeded areas, especially the roughs. The higher height of cut in roughs shades bermudagrass and limits new shoots from capturing sunlight. Furthermore, as ryegrass senesces, a black layer of dead and decaying ryegrass stems and leaves covers the surface, discouraging bermudagrass recovery. Therefore, a multifaceted approach to thinning the ryegrass canopy and breaking apart the black organic surface layer has proven most successful.
If you have overseeded turf and are reading this on April 19 or later, don’t wait any longer to begin shifting the competitive advantage to the understory bermudagrass. Best wishes for a successful 2019 transition and please do not hesitate to contact the USGA Green Section for more information on this technique or any other agronomic practices.
Sincere thanks to Scott Anderson for sharing his challenges and recent success. In addition, thank you to Dr. Chip Howard, who played a key role in developing this transition management strategy.
West Region Agronomists:
Patrick J. Gross, regional director – firstname.lastname@example.org
Larry W. Gilhuly, agronomist – email@example.com
Brian S. Whitlark, agronomist – firstname.lastname@example.org