Control of acetolactate synthase-inhibiting herbicide-resistant Palmer amaranth (Amaranthus palmeri) with sequential applications of dimethenamid-Pin dry edible bean

Abstract

In Western Nebraska, Palmer amaranth is becoming more prevalent where acetolactate synthase (ALS)−inhibitor−resistant biotypes are widespread. There are limited effective postemergence (POST) herbicides labeled for ALS−inhibitor−resistant Palmer amaranth control in dry edible bean. The objective of this study was to evaluate the efficacy of dimethenamid−P in a sequential preemergence (PRE) fb (followed by) POST program at two POST application timings, V1 and V3, for controlling ALS−inhibitor−resistant Palmer amaranth in dry edible bean. A field study was conducted in 2019, 2020, and 2021 in Scottsbluff, NE. PRE−alone programs of pendimethalin + dimethenamid−P provided inconsistent Palmer amaranth control. Dimethenamid−P applied POST following a PRE application of pendimethalin + dimethenamid−P provided effective Palmer amaranth control (>90%) at 4 WAV3 only at the V1 application timing in 2019. In 2020 and 2021 Dimethenamid−P applied POST at V1 and V3 following a PRE application of pendimethalin + dimethenamid−P provided 99% and 98% Palmer amaranth control at 4 WAV3 and 98% and 94% Palmer amaranth control at harvest, respectively. Palmer amaranth biomass was reduced 95−99% and 96−98% compared to the non−treated control when dimethenamid−P was applied POST at V1 and V3, respectively, following a PRE application of pendimethalin + dimethenamid−P in 2020 and 2021. Mixing dimethenamid−P with imazamox + bentazon POST performed similarly to the fomesafen−containing treatments and dimethenamid−P alone POST. Dimethenamid−P applied POST following a PRE application of pendimethalin + dimethenamid−P resulted in similar yield as the fomesafen−containing treatments. If fomesafen is not an option due to the crop rotation interval restriction, using dimethenamid−P in a sequential PRE fb POST program is the only effective alternative to control ALS−inhibitor−resistant Palmer amaranth in Nebraska. The use of dimethenamid−P in a sequential PRE fb POST program, alone or mixed with foliar−active herbicides should be considered by dry edible bean growers who are dealing with ALS−inhibitor−resistant Palmer amaranth.

Control of acetolactate synthase–resistant Palmer amaranth in dry edible bean

“…The level of control provided by a PRE-only treatment was reduced to 14% and 55% control at harvest time in 2017 and 2019, respectively (Table 2). Sequential applications of soil-active herbicides POST may extend Palmer amaranth control later into the growing season and could be an option to manage herbicide-resistant populations (Miranda et al 2022). In 2017, POST treatments provided generally low levels of Palmer amaranth control 3 wk after first POST application when applied with no PRE herbicide.…”

Crop safety and control of acetolactate synthase inhibitor-resistant Palmer amaranth (Amaranthus palmeri) with very long-chain fatty acid-inhibiting herbicides in dry edible bean

“…The objective of this approach is to overlap and prolong residual control until crop canopy closure (McCloskey, 2001). Very long chain fatty acid (VLCFA)-inhibiting herbicides, categorized under Weed Science Society of America (WSSA) Group 15 herbicides, are integral components of sequential PRE fb POST programs, providing effective control of several herbicide-resistant pigweed species (Steckel et al, 2002;Jhala et al, 2015;Chahal et al, 2018;Goodrich et al, 2018;Miranda et al, 2022b). Pigweed species often exhibit resistance to multiple herbicide modes of action, making the evaluation of VLCFA-inhibiting herbicides critical (Jhala et al, 2024) These herbicides, including dimethenamid-P, S-metolachlor and pyroxasulfone, offer a potential solution for effective season-long control of Palmer amaranth in dry edible beans (Wilson and Sbatella, 2014;Soltani et al, 2018b).…”

Discrimination between protoporphyrinogen oxidase–inhibiting herbicide-resistant and herbicide-susceptible redroot pigweed (Amaranthus retroflexus) with spectral reflectance

“…Despite being pervasive, the species has historically been easy to control with herbicides (Mayo et al 1995; Oliveira et al 2017). Control difficulty is exacerbated in crops where the chemical control options are limited (Miranda et al 2022; Owen and Zelaya 2005). Acetolactate synthase (ALS; EC 2.2.1.6; Group 2) and protoporphyrinogen oxidase (PPO; EC 1.3.3.4; Group 14) are herbicides used in soybean [ Glycine max (L.) Merr.]…”