Winter wheat is the predominant crop in Oklahoma, but winter annual grasses are becoming increasingly difficult to control. Summer crop rotations have not been generally adopted; it was decided, therefore, to use winter canola in a crop rotation. However, very little is known about how well herbicides used in canola production will control the winter annual grasses found in Oklahoma wheat fields. Thus, an experiment was conducted at three sites, and repeated the following year, to determine the efficacy of trifluralin, quizalofop, clethodim, and glyphosate in canola production. The weeds evaluated in the experiment were Italian ryegrass, feral cereal rye, and volunteer wheat, along with two varieties of canola: a glyphosate-resistant variety and a conventional variety. All herbicides effectively controlled volunteer wheat. Feral cereal rye and Italian ryegrass varied in response to the herbicide treatments. Trifluralin followed by (fb) quizalofop and glyphosate fb glyphosate were effective on all target species across locations. Effective control of grass weeds was obtained in both conventional and glyphosate-resistant winter canola. Most herbicide treatments improved canola yield over the nontreated check. This experiment demonstrates that Oklahoma wheat producers can effectively rotate to canola to use other herbicides for control of problematic grassy weeds.

Nomenclature: Clethodim; glyphosate; quizalofop; trifluralin; Italian ryegrass, Lolium perenne L. ssp. multiflorum (Lam.) Husnot LOLMU, cereal rye, Secale cereal L. SECCE, volunteer wheat, Triticum aestivum L. TRZAX; canola, Brassica napus L. BRSNN.