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

Abstract

In response to concerns about acetolactate synthase (ALS) inhibitor-resistant weeds in wheat production systems, we explored the efficacy of managing Bromus spp., 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)(2013)(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 ALSinhibiting herbicides for downy and Japanese brome control. Winter wheat injury from herbicide application was minor, with the exception of flucarbazone application at Scott. Bromus spp. control was greatest with pyroxsulam and all herbicide treatments containing pyroxasulfone. Downy and Japanese bromes were controlled least by thiencarbazone and flumioxazin, respectively, whereas Bromus spp. 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 efficacious Bromus spp. control compared with the other herbicides and consistently maintained optimal winter wheat yields. Therefore, pyroxasulfone could facilitate management of Bromus spp. 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.

First report of glyphosate-resistant downy brome (Bromus tectorum L.) in Canada

“…Enhanced monitoring of downy brome populations will comprise a critical mitigation measure to limit the spread of glyphosate-resistant downy brome in Alberta as well as neighboring provinces and states. While effective pre-and post-emergence herbicide options 25,26,48,49 will play an important role in managing glyphosate-resistant downy brome, integration of non-chemical management strategies will be necessary to mitigate selection for resistance to these remaining herbicide options. Growing competitive cultivars 50 , crop rotations involving summer-annuals 51,52 , strategic timing of nitrogen fertilization 53 , and judicious use of tillage 54 may help reduce selection pressure for herbicide-resistant downy brome in cropping systems.…”

Pro-197-Ser Mutation and Cytochrome P450-Mediated Metabolism Conferring Resistance to Flucarbazone-Sodium in Bromus japonicus

“…Through cross-and multiple-herbicide resistance testing, some selective herbicides used in wheat fields cannot effectively distinguish them. In the field study by Johnson et al [6], treatment with pyroxsulam and flucarbazone-sodium obtained a similar result, in which these two kinds of ALS inhibitors were still effective. Therefore, in wheat fields, in addition to ALS inhibitors, other MOA herbicides (such as PS II and ACCase inhibitors) may not be effective for weed control.…”

“…When the density of B. japonicus in wheat fields is 4 plants per square meter, it can cause yield losses of 2.11% to 2.24% [5]. Thus, the grain and biological yields of wheat varieties are negatively affected by competition from B. japonicus [6].…”

Wild Mustard (Sinapis arvensis) Competition and Control in Rain-Fed Spring Wheat (Triticum aestivum L.)

“…Therefore, it is critical for spring wheat to be free of weeds that can interfere with this crop. For sustainable wild mustard control, the integration of POST and -PRE herbicide application is recommended [25]. For instance, Johnson et al [9] reported a broad spectrum weed suppression can be attained through the use of tribenuron and pyroxsulam which are both ALS inhibiting active ingredients.…”