Field evaluation of preemergence and postemergence herbicides for control of protoporphyrinogen oxidase-resistant Palmer amaranth (Amaranthus palmeri S. Watson)

Michael M Houston,Tom Barber,Jason K Norsworthy,Chad Brabham

doi:10.1017/wet.2019.37

Michael M Houston, Tom Barber + Show 2 more

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https://doi.org/10.1017/wet.2019.37

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Journal: Weed Technology	Publication Date: Jun 26, 2019
Citations: 11	License type: CC BY 4.0

Affiliation: University of Arkansas at Fayetteville

Abstract

AbstractPalmer amaranth accessions resistant to protoporphyrinogen oxidase (PPO), 5-enolpyruvyl-shikimate-3-phosphate synthase, and acetolactate synthase (ALS)-inhibitor herbicides are widespread in the Midsouth, making control difficult. Field experiments were conducted in Marion and Crawfordsville, AR, in 2016 and 2017 to assess PRE and POST herbicides labeled for use in corn, cotton, or soybean for control of multiresistant Palmer amaranth. Accessions at both locations were resistant to glyphosate and ALS inhibitors and segregating for both the R128 and ΔG210 PPO resistance mechanisms. Of the 15 herbicide treatments tested, only atrazine (1,120 g ai ha−1), pyroxasulfone (149 g ha−1), and flumioxazin (144 g ha−1) provided 85% or greater Palmer amaranth control 14 days after treatment (DAT). Visible control ratings at 35 DAT declined sharply, with no treatment providing more than 84% control, suggesting POST applications should be made no later than 28 DAT. Glufosinate (594 and 818 g ha−1), dicamba (560 g ae ha−1), 2,4-D plus glyphosate (784 g ae ha−1 plus 834 g ae ha−1), and paraquat (700 g ha−1) applied POST to 7- to 10-cm plants reduced Palmer amaranth density 83% or more 14 DAT. Both glyphosate (1,266 g ha−1) and pyrithiobac sodium (73 g ha−1) provided less than 7% Palmer amaranth control. Although flumioxazin alone at a labeled rate controlled Palmer amaranth 82% in the PRE experiment, PPO inhibitors by themselves applied POST provided no more than 37% control at 14 DAT. Effective foliar herbicides applied POST, including residual herbicides, should be made when Palmer amaranth are less than 10-cm tall for optimal control of these multiresistant Palmer amaranth accessions.

Highlights

Multiple herbicide-resistant Palmer amaranth in corn, cotton, and soybean fields is difficult to control and can drastically reduce yields if not controlled (Culpepper et al 2010; Fast et al 2009; Forseth et al 1984; Klingaman and Oliver 1994; Massinga et al 2001; Ward et al 2013)
In Arkansas and surrounding states, Palmer amaranth accessions resistant to both enolpyruvyl-shikimate3-phosphate synthase (EPSPS)- and acetolactate synthase (ALS)-inhibiting herbicides are common (Burgos et al 2001; Norsworthy et al 2008), and this widespread infestation has caused a dynamic shift in weed control programs (Hoffner et al 2012; Neve et al 2011)
The increased reliance on protoporphyrinogen oxidase (PPO) inhibitors for Palmer amaranth control selected for PPO resistance

Summary

Introduction

Multiple herbicide-resistant Palmer amaranth in corn, cotton, and soybean fields is difficult to control and can drastically reduce yields if not controlled (Culpepper et al 2010; Fast et al 2009; Forseth et al 1984; Klingaman and Oliver 1994; Massinga et al 2001; Ward et al 2013). Unlike residual PRE activity, effective control of PPO-resistant Palmer amaranth with PPO inhibitors POST is only achievable at much higher-than-labeled rates (Schwartz-Lazaro et al 2017). PRE and POST fallow experiments were conducted to determine how to control multiresistant Palmer amaranth accessions harboring both the 210 and R128 PPO resistance mechanisms.

Results

Conclusion