Evaluation of Preemergence Herbicide Programs for Control of Protoporphyrinogen Oxidase-Resistant Amaranthus palmeri in Soybean

L. Tom Barber,Trent L. Roberts,Michael M. Houston,Patrick J. Tranel,Jason K. Norsworthy

doi:10.1155/2021/6652382

L. Tom Barber, Trent L. Roberts + Show 3 more

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https://doi.org/10.1155/2021/6652382

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Abstract

Protoporphyrinogen oxidase- (PPO-) resistant Amaranthus palmeri (S.) Wats. (Palmer amaranth) was confirmed in Arkansas in 2015. Field trials were conducted in Crawfordsville, Gregory, and Marion, Arkansas in 2016, and Crawfordsville and Marion in 2017, assessing PPO-resistant Palmer amaranth control options in Glycine max (L.) Merr. (soybean). Twelve trials consisted of 26 preemergence (PRE) treatments, evaluated for Palmer amaranth control and density reduction at 28 days after treatment (DAT). Treatments that consisted of PPO- or acetolactate synthase- (ALS-) inhibiting herbicides such as flumioxazin (72 g ai ha−1) or sulfentrazone + cloransulam (195 g ha−1 + 25 g ha−1) controlled Palmer amaranth <60%. At 28 DAT, treatments including mixtures of a very-long-chain fatty acid (VLCFA) plus the photosystem II- (PSII-) inhibiting herbicide metribuzin provided increased control over single herbicide sites of action (SOA) or herbicides mixtures to which Palmer amaranth was resistant. Pyroxasulfone + metribuzin (149 g ha−1 + 314 g ha−1) controlled Palmer amaranth 91% control across twelve trials at 28 DAT. S-metolachlor alone did not provide consistent, acceptable control of PPO-resistant Palmer amaranth (55–77%); subsequent research has determined that these populations are resistant to S-metolachlor. A minimum of two effective herbicides should be included in soybean PRE programs for control of PPO-resistant Palmer amaranth.

Highlights

Over-reliance on a single herbicide site of action (SOA)perpetuates the evolution and spread of herbicide-resistant biotypes [1,2,3]
Inhibiting herbicides and glyphosate was selected for Palmer amaranth with mechanisms of resistance to one or both of these SOA [4,5,6]
Two herbicides were used on more acreage in the US, sulfentrazone (17%), which is another PPO-inhibiting herbicide, and glyphosate (85%) [8]

Summary

Introduction

Over-reliance on a single herbicide site of action (SOA)perpetuates the evolution and spread of herbicide-resistant biotypes [1,2,3]. Inhibiting herbicides and glyphosate was selected for Palmer amaranth with mechanisms of resistance to one or both of these SOA [4,5,6]. After the identification of GR-resistant Palmer amaranth, use of PPO-inhibiting herbicides increased, offering both residual and foliar control of GR-resistant Palmer amaranth [9, 10]. PPO inhibitors offered both versatile and reliable control of Palmer amaranth [11, 12]. A PPO-inhibiting herbicide in the diphenylether family, use increased from 2 to 16% of all US soybean acreage after confirmation of GR-resistant Palmer amaranth [7, 8], with the heaviest reliance on this herbicide in the Midsouth. Two herbicides were used on more acreage in the US, sulfentrazone (17%), which is another PPO-inhibiting herbicide, and glyphosate (85%) [8]

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