Confirmation of 2,4‐D resistance and identification of multiple resistance in a Kansas Palmer amaranth (Amaranthus palmeri) population

Abstract

BACKGROUND: Amaranthus palmeri S. Wats is among the most problematic annual broadleaf weed species in the USA, including in Kansas. In late summer 2015, seeds of an A. palmeri population (MHR) that had survived field-use rates of 2,4-D were collected from Barton County, KS, USA. The main objectives were to: (i) confirm and characterize 2,4-D resistance in a MHR population; (ii) characterize the resistance profile of the MHR population in relation to a multiple herbicide-susceptible (MHS) population to glyphosate, chlorsulfuron, atrazine, mesotrione, fomesafen; and (iii) determine the effectiveness of alternative POST burndown herbicides for controlling MHR population. RESULTS: The MHR population had 3.2-fold resistance to 2,4-D. In addition, the MHR population also exhibited multiple resistance to glyphosate (11.8-fold), chlorsulfuron (5.0-fold), atrazine (14.4-fold), and mesotrione (13.4-fold). Furthermore, the MHR population also showed reduced sensitivity to fomesafen (2.3-fold). In a separate study, dicamba with glyphosate, atrazine or fluroxypyr + 2,4-D, and paraquat alone or with atrazine, metribuzin, saflufenacil or 2,4-D provided ≥ 99% injury to the MHR population. Similarly, saflufenacil alone or with atrazine, metribuzin or 2,4-D, and glufosinate alone or with glyphosate + 2,4-D, and glyphosate + dicamba, and a premix of bicyclopyrone + atrazine + mesotrione + S-metolachlor also effectively controlled the MHR population. CONCLUSION: This research confirms the first global case of an A. palmeri population from Kansas with multiple resistance to 2,4-D, glyphosate, chlorsulfuron, atrazine and mesotrione, and reduced sensitivity to fomesafen. Dicamba, glufosinate, paraquat, and saflufenacil alone or in tank-mixtures with PRE herbicides effectively controlled this MHR population.

Differential sensitivity of Kansas Palmer amaranth populations to multiple herbicides

“…The progeny seeds obtained from those female survivors (5 from KW2 and 7 from PR8 population) were used to further characterize the sensitivity levels in both populations (KW2 and PR8) to 2,4‐D and other key herbicides (glyphosate, chlorsulfuron, atrazine, and mesotrione) tested. A Palmer amaranth population (MHS) previously known to be susceptible to 2,4‐D and all other aforementioned herbicides was also included (Kumar et al., 2019). This MHS population was originally collected from Kansas State University Ashland Bottom research fields in Riley County, Kansas and was previously used in various greenhouse and laboratory studies (Mithila Jugulam, personal communication).…”

“…Similarly, a Palmer amaranth population with resistance to atrazine, mesotrione, tembotrione, and topramezone was reported from Nebraska in 2014 (Jhala et al., 2014). More recently, a single Palmer amaranth population in Kansas has been identified with multiple resistance to five different herbicide MOAs (2,4‐D, glyphosate, chlorsulfuron, atrazine, mesotrione), and with reduced sensitivity to PPO inhibitors (fomesafen) (Kumar, Liu, Boyer, & Stahlman, 2019).…”

Characterization and Management of Glyphosate- and HPPD-Inhibitor-Resistant Palmer Amaranth in Kansas Corn Production

“…In a separate mesotrione (Callisto) dose-response study, the MHR population also exhibited 3.5-fold resistance to mesotrione herbicide on the basis of visual control data (LD 50 values) ( Figure 2). In comparison, a Palmer amaranth population from Barton County, KS, has recently been reported with multiple resistance to 2,4-D, glyphosate (Roundup PowerMax), chlorsulfuron (Glean), atrazine (Aatrex), and mesotrione (Callisto) (Kumar et al, 2019).…”

“…Furthermore, multiple herbicide-resistant (MHR) Palmer amaranth is also an increasing concern for Kansas growers. Palmer amaranth populations that have resistance to one or more of the following herbicide site(s) of action, including sulfonylureas (ALS inhibitors), atrazine (PS II inhibitor), mesotrione (HPPD inhibitor), glyphosate (EPSPS inhibitor), and more recently to 2,4-D (synthetic auxins) have been reported in Kansas (Heap, 2019;Kumar et al, 2019).…”

Effective Herbicide Options for Controlling Glyphosate-Resistant Palmer Amaranth in Roundup Ready 2 Xtend Soybean

“…Furthermore, multiple herbicide-resistant (MHR) Palmer amaranth is also a serious management challenge to Kansas growers. Currently, Palmer amaranth populations are reported with resistance to one or more of the following herbicide site(s) of action, including sulfonylureas (ALS inhibitors), atrazine (PS II inhibitor), mesotrione (HPPD inhibitor), glyphosate (EPSPS inhibitor), and more recently to 2,4-D (synthetic auxins) in Kansas (Heap, 2019;Kumar et al, 2019).…”