March Madness is almost upon us and that means it’s time to go all-in on bermudagrass transition! Recent site visits reveal that the understory bermudagrass is already pushing up new shoots, which consumes carbohydrates stored from the fall. The bermudagrass plant will typically produce three or four new shoots from stored carbohydrates when emerging from dormancy. If those new shoots are unable to produce enough food due to competition from overseeded ryegrass, the bermudagrass plant will eventually die. Despite being hidden underneath the ryegrass, this process is occurring right now! Start a successful transition by taking steps in four key areas to improve bermudagrass recovery:
Sunlight: Lower mowing heights on all overseeded tees, fairways and roughs. By mid-March, heights should be at or below 0.5 inch on closely mown turf and at or below 1 inch in rough areas. Continue to lower rough mowing height and consider an abrupt drop in late April or early May when the main golf events have wrapped up for the season. For more on this strategy, read the Green Section Record article “Rough Transition.” I also recommend using light-intensity vertical mowing and/or brushing to stand up the ryegrass and disrupt the organic layer that forms at the surface to reduce any delay in bermudagrass recovery.
Water: Typically, the slowest areas to transition are the driest. Maintain adequate soil moisture on overseeded areas from April through the end of June. Consider using a soil moisture meter to quantify wet and dry areas. A good guideline is to maintain moisture levels between 30% and 45% until transition is complete.
Chemical Assistance: The use of penoxsulam (Sapphire) has taken off and now is the “go-to” chemical strategy to aid transition. It is more of a growth regulation program than a program to kill the ryegrass. The rates and application frequency vary widely. Those deploying a more conservative approach will spray at 2 ounces per acre about every two weeks. Courses spraying at 4 ounces per acre typically apply on a three-week interval. Others will apply 8 ounces per acre on three- to four-week intervals. Most will begin in March or have already made one application. Some will need a “cleanup” application between mid-May and early June to completely remove the ryegrass and any lingering Poa annua. This is often done with one of the sulfonylurea herbicides (acetolactate synthase (ALS) inhibitors).
Fertility: Approximately two weeks following chemical growth regulation of the ryegrass, begin to increase nitrogen fertility. This timing will avoid undesirable growth of the ryegrass while encouraging the understory bermudagrass.
The transition season is always a tenuous time for golf courses in the desert, but experience has proven that a proactive program that starts early in the spring is the best way to deliver a good-quality golfer experience as the playing surfaces shift from ryegrass to bermudagrass.
West Region Agronomists:
Brian Whitlark, regional director, West Region – bwhitlark@usga.org
Ross Niewola, agronomist – rniewola@usga.org