Jointed Goatgrass Management with Imazamox‐Resistant Cultivars in a Winter Wheat–Fallow Rotation

Abstract

Jointed goatgrass (Aegilops cylindrica Host) is an economically important weed in winter wheat (Triticum aestivum L.)–fallow production regions of the United States. Few options exist for management of jointed goatgrass in winter wheat due to the close genetic relationship between the two species. This research evaluated use of imazamox herbicide (2‐[(RS)‐4‐isopropyl‐4‐methyl‐5‐oxo‐2‐imidazolin‐2‐yl]‐5‐methoxymethylnicotinic acid) in an imazamox‐resistant (IR) winter wheat–fallow rotation over 6 yr when grown continuously or in rotation with a conventional winter wheat cultivar. The objectives of this study were to compare use patterns of IR technology in winter wheat with respect to jointed goatgrass density and wheat grain contamination over three crop years in a winter wheat–fallow system and to monitor jointed goatgrass and jointed goatgrass × wheat hybrid populations for resistance to imazamox. The IR treatment resulted in reduced jointed goatgrass density compared to conventional treatments in 5 out of 6 yr. Reductions in jointed goatgrass tiller density resulting from use of imazamox in IR winter wheat were evident in a subsequent crop year at each of two experimental sites. No IR jointed goatgrass plants nor viable jointed goatgrass × wheat hybrid plants were found. In a winter wheat–fallow rotation, IR technology can effectively manage jointed goatgrass populations and reduce jointed goatgrass contamination of grain. Use of the technology every other crop year, or two out of every three crop years, will provide management benefits in subsequent years.