Response of Japanese Stiltgrass (Microstegium vimineum) to Application Timing, Rate, and Frequency of Postemergence Herbicides1

Japanese stiltgrass is a nonnative invasive grass that occurs in a variety of habitats and is widely distributed throughout the eastern United States. In natural areas such as forests, herbicide options that selectively control Japanese stiltgrass while preserving native herbaceous and woody vegetation may be desired. The efficacy of three selective postemergence herbicides (fenoxaprop-P, imazapic, and sethoxydim) applied early season, midseason, or late season on monoculture understory stands of Japanese stiltgrass in forests was examined in an experiment conducted at a site in North Carolina and a site in Virginia from 2002 to 2004. The herbicides, averaged across application timings, controlled Japanese stiltgrass at the end of the growing season 83 to 89% and seedhead production 79 to 94% compared with nontreated plants. Seedling emergence was reduced in the spring of 2004 by 89, 70, and 78% by fenoxaprop-P, imazapic, and sethoxydim, respectively, applied in 2003. In another experiment at the North Carolina site in 2002 and 2003, fenoxaprop-P or sethoxydim applied twice (4 wk apart) at half-registered rates controlled Japanese stiltgrass. This study demonstrates that land managers have multiple POST herbicide and application timing, rate, and frequency options for Japanese stiltgrass control. Nomenclature: Fenoxaprop-P; imazapic; sethoxydim; Japanese stiltgrass, Microstegium vimineum (Trin.) A. Camus #3 MCGVM. Additional index words: Invasive plant, annual jewgrass, bamboograss, flexible sesagrass, Japanese grass, Mary's grass, Nepalese browntop. Abbreviations: 1X, maximum use rate.