Sulfosulfuron and Bispyribac-Sodium Combined with Overseeding Creeping Bentgrass (Agrostis stolonifera L.) for Fairway Conversion.

Roughstalk bluegrass (Poa trivialis L.) contamination is problematic on golf course fairways from the Midwest to the Mid-Atlantic United States.  Bispyribac-sodium and sulfosulfuron have potential to selectively control roughstalk bluegrass.  Our objective was to determine the most effective herbicide treatments for short- and long-term roughstalk bluegrass control and to determine if overseeding with creeping bentgrass (Agrostis stolonifera L.) after herbicide treatments improves long-term control of roughstalk bluegrass or conversion to creeping bentgrass.  Studies were initiated in Indiana in 2006, 2007 and 2008.  Plots were treated with bispyribac-sodium or sulfosulfuron and then half of each plot was overseeded with creeping bentgrass in early August, two weeks after the final herbicide application.  The most effective herbicide treatments for short-term roughstalk bluegrass control were sulfosulfuron at 27 g a.i. ha^-1 applied three times or bispyribac-sodium at 74 g a.i. ha^-1 applied four times, which resulted in less than 30% roughstalk bluegrass cover in all three years.  Overseeding with creeping bentgrass improved long-term roughstalk bluegrass control and quickened conversion to creeping bentgrass resulting in 69 and 85% creeping bentgrass cover in 2006 and 2007, respectively.  Seeding had no effect in 2008 as roughstalk bluegrass quickly recovered from herbicide injury and out-competed creeping bentgrass seedlings in an unseasonably cool August.