Multiple herbicide resistance in waterhemp (Amaranthus tuberculatus) accessions from Wisconsin

Abstract

A comprehensive WI state-wide assessment of waterhemp response to a diverse group of herbicide sites of action (SOAs) has not been conducted. Our objective was to characterize the response of a WI state-wide collection of waterhemp accessions to postemergence (POST) and preemergence (PRE) herbicides commonly used in corn and soybean. Greenhouse experiments were conducted with more than 80 accessions from 27 counties. POST treatments were 2,4-D, atrazine, dicamba, fomesafen, glufosinate, glyphosate, imazethapyr, and mesotrione at 1× and 3× label rates. PRE treatments were atrazine, fomesafen, mesotrione, metribuzin, and S-metolachlor at 0.5×, 1×, and 3× label rates. Ninety-eight and 88% of the accessions exhibited ≥ 50% plant survival after exposure to imazethapyr and glyphosate POST 3× rate, respectively. Seventeen, 16, and 3% of the accessions exhibited ≥ 50% plant survival after exposure to 2,4-D, atrazine, and dicamba POST 1× rate, respectively. Survival of all accessions was ≤ 25% after exposure to 2,4-D or dicamba POST 3× rate, or glufosinate, fomesafen, and mesotrione POST at either rate evaluated. No plant of any accession survived exposure to glufosinate at either rate. Forty-five and 3% of the accessions exhibited < 90% plant density reduction after exposure to atrazine PRE 3× rate and fomesafen PRE 1× rate, respectively. Plant density reduction of all accessions was ≥ 96% after exposure to fomesafen PRE 3× rate, or metribuzin, S-metolachlor, and mesotrione PRE 1× rate. Our results suggest that waterhemp resistance to imazethapyr and glyphosate POST is widespread in WI, whereas resistance to 2,4-D, atrazine, and dicamba POST is present to a lower extent. One accession (A75, Fond du Lac County) exhibited multiple resistance to imazethapyr, atrazine, glyphosate, and 2,4-D POST. Overall, atrazine PRE was ineffective for waterhemp control in WI. Proactive resistance management and the use of effective PRE and POST herbicides are fundamental for waterhemp management in WI.

Preemergence herbicide premixes reduce the risk of soil residual weed control failure in corn

“…The low degree of waterhemp control provided by the PRE herbicide premix flumetsulam þ clopyralid and atrazine may be related to waterhemp resistance to herbicides that inhibit acetolactate synthase (ALS) (Faleco et al 2022b) and photosystem II (PS II), respectively (Faleco et al 2022a(Faleco et al , 2022b. ALS-and PS IIresistant waterhemp has been widely reported across the midwestern United States (Evans et al 2019;Heap 2022;Vennapusa et al 2018).…”

Layered‐residual herbicide programs for waterhemp control in glufosinate‐resistant soybean

“… a The natural waterhemp populations in Lancaster and Brooklyn were previously determined to be resistant to acetolactate synthase (ALS)‐inhibiting herbicides; the Brooklyn waterhemp was also determined to be glyphosate‐resistant (Faleco et al., 2022). …”

Impact of cereal rye cover crop on the fate of preemergence herbicides flumioxazin and pyroxasulfone and control of Amaranthus spp. in soybean

“…and Palmer amaranth ( Amaranthus palmeri S. Watson), hereafter referred to as Amaranthus spp., are two of the most troublesome weed species in row-crop production systems in the U.S. Midwest (Steckel 2007; Van Wychen 2022). These diecious Amaranthus species are highly competitive weeds (Steckel 2007) and prolific seed producers (Schwartz et al 2016) and have rapidly evolved resistance to the main postemergence herbicides (i.e., glyphosate and imazethapyr) adopted for their management in soybean (Faleco et al 2022; Heap 2023; Peterson et al 2018). After the release of glyphosate-resistant crops in the late 1990s, farmers reduced the use of preemergence herbicides due to the excellent postemergence efficacy of glyphosate for controlling weeds such as Amaranthus spp.…”

“…(Duke and Powles 2008; Green 2014). However, after years of reliance on glyphosate, herbicide-resistance cases have increased dramatically (Faleco et al 2022; Heap 2023; Peterson et al 2018), and the use of preemergence herbicides has again become an important tool for weed management programs in soybean (Beckie et al 2019; Perkins et al 2021).…”