Preemergence (PRE) and postemergence (POST) herbicides registered for large crabgrass control were evaluated for control of Japanese stiltgrass, an invasive, nonnative C4 annual grass. Benefin plus oryzalin, dithiopyr, isoxaben plus trifluralin, oryzalin, oxadiazon, pendimethalin, prodiamine, or trifluralin applied PRE controlled Japanese stiltgrass 87% or greater 8 wk after treatment. Benefin plus trifluralin, metolachlor, or napropamide applied PRE were less effective (78, 39, and 59% control, respectively). Single POST applications of clethodim, fenoxaprop-P, fluazifop-P, or sethoxydim controlled Japanese stiltgrass 50 to 88%. These herbicides applied twice provided 82 to 99% control. Single POST applications of glufosinate controlled Japanese stiltgrass 82 to 85%, whereas two applications provided complete control. Single POST applications of glyphosate were just as effective as two applications in controlling Japanese stiltgrass. Dithiopyr, MSMA, and quinclorac applied POST were ineffective on Japanese stiltgrass. All PRE and POST herbicides tested were equally or more effective on Japanese stiltgrass than on large crabgrass, with the exception of metolachlor applied PRE and dithiopyr or quinclorac applied POST.

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.