Multi-year Roughstalk Bluegrass Control in Creeping Bentgrass with Bispyribac-sodium and Sulfosulfuron

Bispyribac-sodium and sulfosulfuron are labeled for roughstalk bluegrass control in creeping bentgrass but comprehensive investigations are limited for long-term control. The objective of these field experiments was to investigate roughstalk bluegrass control with these herbicides on a creeping bentgrass fairway over three years. Bispyribac-sodium was applied twice at 37, 74, or 111 g a.i./ha or thrice at 37 or 74 g/ha. Sulfosulfuron was applied twice or thrice at 6.5 or 13 g a.i./ha or once at 26 g/ha. Creeping bentgrass chlorosis from herbicides was less than 20% by two to three weeks after applications while all treatments generally provided substantial reductions in roughstalk bluegrass cover by late July. However, roughstalk bluegrass regrowth was detected by October in all three years suggesting herbicide applications visually eliminated foliage but did not control the entire plant. Overall, bispyribac-sodium and sulfosulfuron effectively suppressed roughstalk bluegrass ground cover in summer months but regrowth during fall months prevented long-term successful control.