Herbicide Tolerance In 11 Grass Species For Minimal-To-No-Mow Golf Course Rough

Research was conducted to determine the tolerance of 11 grass species used in minimal-to-no-mow turf areas to three postemergence herbicides applied at one- and twofold the maximum label rates in 2018 and 2019. Grasses were transplanted into field plots in West Lafayette, IN, in 2018 and 2019, allowed time to establish (similar to 1-2 mo), and then either treated with one application of quinclorac, sethoxydim, and topramezone at two rates or not treated. All 11 grass species had acceptable tolerance (<= 20% injury) to quinclorac applied at 0.845 kg acid equivalent (a.e.) ha(-1). Quinclorac at 1.69 kg a.e. ha(-1) produced moderate injury (>= 21% injury) on only little bluestem [Schizachyrium scoparium (Michx.) Nash.], prairie dropseed [Sporobolus heterolepis (A. Gray) A. Gray], and switchgrass (Panicum virgatum L.). Strong creeping red fescue (Festuca rubra L. ssp. rubra Gaudin), which had <= 5% injury from all three herbicides, exhibited the greatest tolerance among grass species tested. With the exception of strong creeping red fescue, sethoxydim significantly injured all other grass species. Injury from topramezone varied among grass species and herbicide rates. Grasses tolerant (<= 20% injury) to topramezone at both rates were big bluestem (Andropogon gerardii Vitman), broomsedge bluestem (Andropogon virginicus L.), indiangrass [Sorghastrum nutants (L.) Nash], strong creeping red fescue, and tall fescue [Festuca arundinacea Schreb.; syn. Schedonorus arundinaceus (Schreb.) Dumort., nom. cons.]. Tolerance among species was variable to quinclorac, sethoxydim, and topramezone, and thus turf managers should first identify desired grass species prior to herbicide application.