David M. Kopec, Extension Turfgrass Specialist
On the first hot and sweltering days, everyone starts to think about transition of ryegrass back to bermudagrass. There are probably more ways to do this, than there are overseeding preparation techniques in the fall. Whatever you do, keep this in mind.
Bermudagrass grows best when the nighttime temperatures (on the course) have a low temperature of 60 F for seven days in a row.
So, whatever you do for transition, you should keep this in mind because the response of bermuda should begin at the minimum level under the above weather conditions.
Cool Season Grasses and Spring Growth
Ryegrass and Poa trivialis grow like mad when the temperatures are 85 in the day and 55 at night. What they are doing is elongating their existing shoots and really not making more shoots (in the late spring). Therefore, one thought is to enhance the elongation and cut off the green vegetation (increased mowing stress) at the same time.
Twenty years ago, ryegrass varieties could be easily eliminated rather quickly from fairways and roughs by lowering the mowing height and increasing the mowing frequency. This would "burn-out" the grass rather easily. Today, the lower growing, higher density and more heat tolerant varieties tolerate the decreased mowing heights at regular mowing frequencies. This makes transition take longer.
Forcing a transition by "mowing" probably has taken another turn. Chip Howard has conducted tests that show "outright scalping of the ryegrass" (as a mowing treatment alone) provided the best transition on fairways and roughs. It might look ugly, but the bermuda grows back quickly, and has a long time to fully recuperate.
Scalping is a cost effective option. You need the support of the club if you are going to do this. Perhaps, right after the last big spring tournament, is the time to scalp the fairways and roughs (weather conditions being met).
Intuitively, the addition of 1.0 lb. of nitrate applied 2-3 days before the scalping will help burn out the turf. The grass will elongate tremendously and probably require additional scalps.
There are chemical alternatives to transition of fairways and roughs. Surflan will stop ryegrass in its tracks, turn the end of the leaf tips white and stop its growth. However, Surflan would limit bermudagrass stolons from pegging for about a month.
Image wipes out cool season grasses. The half rate of 0.25 lb. ai/A worked well for me on replicated test plots. Kerb has given me mixed results. It wipes out rye, but can twist, cup and stunt the bermudagrass for up to 5-6 weeks (not acceptable). MSMA at 2.0 lbs. with a surfactant will also do a number on the ryegrass.
For greens, I have found that repeated light verticutting is the best way to get rid of Poa trivialis, or ryegrass at transition. Other things equal, ryegrass has yielded more bermudagrass than Poa trivialis, under all management treatments. Keep your nitrogen levels up so you will favor bermuda and weaken the ryegrass.
Issued in furtherance of Cooperative Extension work, acts of May 8 and June 30, 1914, in cooperation with the U.S. Department of Agriculture, James A. Christenson, Director, Cooperative Extension, College of Agriculture & Life Sciences, The University of Arizona. The University of Arizona is an equal opportunity, affirmative action institution. The University does not discriminate on the basis of race, color, religion, sex, national origin, age, disability, veteran status, or sexual orientation in its programs and activities.