Selective Control of Jointed Goatgrass (Aegilops cylindrica) with Imazamox in Herbicide-Resistant Wheat'

Jointed goatgrass (Aegilops cylindrica) is a serious problem for winter wheat producers throughout the western U.S. Interference from this weed can severely reduce grain yield and con- taminate harvested grain, resulting in dockage losses. There are currently no selective herbicides registered for controlling jointed goatgrass in wheat. Imazamox, an imidazolinone herbicide, was applied to an imidazolinone herbicide-resistant (IMI) wheat mutant of the winter wheat cultivar 'Fidel.' Jointed goatgrass control from spring postemergence application of imazamox ranged from 61 to 97% when applied at 36 g/ha. Negligible crop injury from imazamox treatment was observed at 36 g/ha at several locations under dryland environments in the U.S. Pacific Northwest. Wheat yield was increased 19 to 41 % by imazamox treatment in three of four experiments. Percent dockage resulting from jointed goatgrass spikelet contamination of harvested wheat grain was eliminated by imazamox treatment. Introduction of the IMI trait into commercial wheat cultivars could provide an effective method for selective control of jointed goatgrass in winter wheat. Nomenclature: Imazamox, 2-(4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-lH-imidazol-2-yl)-5- (methoxymethyl)-3-pyridinecarboxylic acid; jointed goatgrass, Aegilops cylindrica Host #3 AEGCY; winter wheat, Triticum aestivum L. IMI-Fidel. Additional index words: Herbicide-tolerant crop, IMI wheat, AEGCY, AVEFA, LOLMU, BROTE. Abbreviations: AHAS, acetohydroxyacid synthase; IMI, imidazolinone herbicide-resistant; PNW, Pacific Northwest.