Pyroxasulfone Is Effective for Management ofBromusspp. in Winter Wheat in Western Canada

Abstract

AbstractIn response to concerns about acetolactate synthase (ALS) inhibitor–resistant weeds in wheat production systems, we explored the efficacy of managingBromusspp., downy and Japanese bromes, in a winter wheat system using alternative herbicide treatments applied in either fall or spring. Trials were established at Lethbridge and Kipp, Alberta, and Scott, Saskatchewan, Canada over three growing seasons (2012–2014) to compare the efficacy of pyroxasulfone (a soil-applied very-long-chain fatty acid elongase inhibitor; WSSA Group 15) and flumioxazin (a protoporphyrinogen oxidase inhibitor; WSSA Group 14) against industry-standard ALS-inhibiting herbicides for downy and Japanese brome control. Winter wheat injury from herbicide application was minor, with the exception of flucarbazone application at Scott.Bromusspp. control was greatest with pyroxsulam and all herbicide treatments containing pyroxasulfone. Downy and Japanese bromes were controlled least by thiencarbazone and flumioxazin, respectively, whereasBromusspp. had intermediate responses to the other herbicides tested. Herbicides applied in fall resulted in reduced winter wheat yield relative to the spring applications. Overall, pyroxasulfone or pyroxsulam provided the most efficaciousBromusspp. control compared with the other herbicides and consistently maintained optimal winter wheat yields. Therefore, pyroxasulfone could facilitate management ofBromusspp. resistant to ALS inhibitors in winter wheat in the southern growing regions of western Canada. Improved weed control and delayed herbicide resistance may be achieved when pyroxasulfone is applied in combination with flumioxazin.