Tolerance of Red Fescue (Festuca rubra) and Bentgrass (Agrostisspp.) to Sethoxydim

Publisher Website
Google Scholar
Abstract
Sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one} is used to control weedy grasses in red fescue (Festuca rubra L. # FESRU and F. rubra ssp. commutata), an important seed crop in Oregon. The sethoxydim rate required to reduce growth rate of 11 cultivars of red fescue and four cultivars of bentgrass (Agrostis tenuis Sibth. # AGSTE and A. stolonifera L. var. palustris # AGSST), a common contaminant in red fescue fields, by 50% (GR50) was determined in greenhouse and laboratory experiments. Field experiments compared only red fescue cv. ‘Pennlawn’ and bentgrass cv. ‘Penncross'. The GR50 values for Pennlawn red fescue in the field, the greenhouse, and the laboratory were 30 kg ai/ha, 15 kg/ha, and 5300 μM, respectively. Penncross bentgrass was approximately 400, 1400, and 12 900 times more susceptible than Pennlawn red fescue in the field, in the greenhouse, and in laboratory experiments, respectively. Plants were at different growth stages in the different experiments. The xylene and surfactant used as a solvent for the technical grade sethoxydim was as toxic to red fescue without sethoxydim as when sethoxydim was included. Cultivars of red fescue differed in their response to sethoxydim, but cultivars of bentgrass did not. The GR50's of other species tested in the greenhouse were >4 kg/ha for annual bluegrass (Poa annua L. # POAAN), 0.22 kg/ha for tall fescue (F. arundinacea Schreb. # FESAR), 0.37 kg/ha for downy brome (Bromus tectorum L. # BROTE), and 0.017 kg/ha for Italian ryegrass (Lolium multiflorum Lam. # LOLMU).