Using Pyroxasulfone for Downy Brome (&amp;lt;i&amp;gt;Bromus tectorum&amp;lt;/i&amp;gt; L.) Control in Winter Wheat

Vipan Kumar,Prashant Jha,Amit J Jhala

doi:10.4236/ajps.2017.810159

Abstract

Downy brome is one of the most troublesome weeds in no-till wheat production systems of the US Great Plains. Pyroxasulfone is a relatively new, soil-applied residual herbicide (root/shoot growth inhibitor) labeled for use in wheat. Multiple field experiments were conducted near Huntley, MT from 2012 through 2016 to determine the efficacy of pyroxasulfone to control downy brome in imidazolinone (IMI)-tolerant (Clearfield&#8482) winter wheat. Pyroxasulfone did not cause any injury to wheat in any of the three studies. Downy brome injury with pyroxasulfone preemergence (PRE) only program did not differ between 89 or 178 g·ai (active ingredient)·ha-1 rates, and averaged 82% and 84% in 2 separate studies. In a preplant (PP) burndown program, the addition of pyroxasulfone (178 g·ai·ha-1) to glyphosate improved downy brome end-season injury from 15% to 74%. In a separate study, the end-season injury with pyroxasulfone was greater when applied PRE (84%) compared to the delayed PRE (DPRE) timing (74%). In addition, the water dispersible granule (WDG) formulation of pyroxasulfone performed slightly better than the suspension concentrate (SC) formulation for downy brome injury. Pyroxasulfone applied PRE in the fall at a rate of 89 g·ai·ha-1 followed by (fb) imazamox (44 g·ai·ha-1 rate) applied postemergence (POST) in the spring effectively controlled downy brome (99% end-season injury). Furthermore, the injury was consistent with the standard program comprising of propoxycarbazone (29 g·ai·ha-1) PRE fb imazamox POST in IMI-tolerant winter wheat. In conclusion, pyroxasulfone applied PRE in the fall can be effectively utilized in conjunction with a standard acetolactate synthase (ALS)-inhibitor-based POST herbicide program for a season-long downy brome management in winter wheat.

Highlights

Wheat (Triticum aestivum L.) is an important cereal grain crop well suited for dryland cropping systems of the northwestern United States, including Montana
Pyroxasulfone (89 g∙ha−1) or propoxycarbazone (29 g∙ai∙ha−1) PRE followed by imazamox (44 g∙ai∙ha−1) POST were the most effective treatments (>97% injury) for managing downy brome in IMI-tolerant wheat at 2, 5, and 8 weeks after the POST (WAPOST) (Table 3)
Downy brome injury with pyroxasulfone (89 or 178 g∙ai∙ha−1) PRE alone was greater than propoxycarbazone PRE alone, but comparable to imazamox (44 g∙ha−1) POST standalone treatment across all evaluation dates, and averaged 81% at 8 WAPOST

Summary

Introduction

Wheat (Triticum aestivum L.) is an important cereal grain crop well suited for dryland cropping systems of the northwestern United States, including Montana. Downy brome (commonly known as cheatgrass) is an invasive, self-pollinated, winter annual grass weed, widespread in rangeland and winter wheat production areas of this region [6]. It is a native of Mediterranean region of Europe, and was first identified in the United States in 1861 in New York and Pennsylvania [7]. Fall-emerging downy brome seedlings overwinter in a semi-dormant state and resume growth in the spring after winter vernalization. Those plants attain physiological maturity by mid-June in this region [11]. Downy brome is a prolific seed producer (up to 2.6 billion seeds ha−1) [12]

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