The potential for future commercialization of glyphosate-resistant wheat necessitates evaluation of agronomic merits of this technology. Experiments were established to evaluate glyphosate-resistant wheat and weed responses to glyphosate rate, application timing, and tank mixtures. Glyphosate at 1,680 g/ha did not injure wheat. Wheat response to glyphosate applied to one- to three- or three- to five-leaf wheat was not different from that of untreated wheat. Wheat was injured more from glyphosate plus thifensulfuron or glyphosate plus dicamba than from individual herbicides at one of six locations, but grain yield was not affected by glyphosate tank mixtures. Glyphosate application timing did not affect control of wild oat or common lambsquarters 56 d after treatment. Glyphosate when applied to one- to three-leaf wheat provided better control of wild buckwheat than later glyphosate application, whereas glyphosate applied to three- to five-leaf wheat provided the best control of green and yellow foxtail, redroot pigweed, and Canada thistle. Weed control with glyphosate tended to be better than with conventional herbicides, and wheat treated with glyphosate produced approximately 10% more grain than wheat treated with conventional herbicide tank mixes.
Nomenclature: Dicamba; glyphosate; thifensulfuron; Canada thistle, Cirsium arvense (L.) Scop. #3 CIRAR; green foxtail, Setaria viridis (L.) Beauv. # SETVI; redroot pigweed, Amaranthus retroflexus L. # AMARE; wild buckwheat, Polygonum convolvulus L. # POLCO; yellow foxtail, S. glauca (L.) Beauv. # SETLU; spring wheat, Triticum aestivum L.
Additional index words: Genetically modified organism, GMO, herbicide injury, herbicide-resistant crops, transgenic wheat, wheat yield.
Abbreviations: DAT, days after treatment; GMO, genetically modified organism.