Annual Bluegrass Control in Overseeded Golf Course Fairways when Mitosis-Inhibiting Herbicides are Not Effective

Abstract

Annual bluegrass is a problematic weed in highly maintained turfgrasses, especially when overseeding with cool-season species. Two studies were conducted on bermudagrass fairways overseeded with perennial ryegrass in South Carolina to evaluate pre- and postemergence control options for annual bluegrass when mitosis-inhibiting (MI) herbicides were no longer effective. Prodiamine at 0.84 kg ai/ha applied 60 days before overseeding (DBO) and dithiopyr at 0.56 kg ai/ha applied 45 DBO and 90 days after overseeding (DAO) provided less than 33% annual bluegrass control regardless of study or year. Greater than 90% annual bluegrass control and 80% turf density were achieved with ethofumesate at 1.1 kg ai/ha 30 and 50 DAO and ethofumesate at 1.1 kg ai/ha 30 DAO followed by bispyribac-sodium at 0.074 kg ai/ha 120 DAO. All treatments containing ethofumesate at 1.1 kg ai/ha 30 DAO provided greater than 85% annual bluegrass control regardless of year. Greater than 70% annual bluegrass control and 80% turf density was achieved with foramsulfuron at 0.028 kg ai/ha and rimsulfuron at 0.018 kg ai/ha both applied 7 DBO. Oxadiazon at 2.2 kg ai/ha 60 DBO provided 69% annual bluegrass control. This research indicates that other herbicide regimes will provide acceptable annual bluegrass control and perennial ryegrass density when MI herbicides lose their effectiveness on overseeded golf course fairways.