Management of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in 2,4-D–, glufosinate-, and glyphosate-resistant soybean

Abstract

Glyphosate-resistant (GR) Palmer amaranth is a problematic annual broadleaf weed in soybean production fields in Nebraska and many other states in the United States. Soybean resistant to 2,4-D, glyphosate, and glufosinate (Enlist E3TM) has been developed and was first grown commercially in 2019. The objectives of this research were to evaluate the effect of herbicide programs applied PRE, PRE followed by (fb) late-POST (LPOST), and early-POST (EPOST) fb LPOST on GR Palmer amaranth control, density, and biomass reduction, soybean injury, and yield. Field experiments were conducted near Carleton, Nebraska in 2018, and 2019 in a grower’s field infested with GR Palmer amaranth in 2,4-D, glyphosate, and glufosinate-resistant soybean. Sulfentrazone + cloransulam-methyl, imazethapyr + saflufenacil + pyroxasulfone, and chlorimuron ethyl + flumioxazin + metribuzin applied PRE provided 84% to 97% control of GR Palmer amaranth compared to the nontreated control 14 d after PRE. Averaged across herbicide programs, PRE fb 2,4-D and/or glufosinate, and sequential application of 2,4-D or glufosinate applied EPOST fb LPOST resulted in 92% and 88% control of GR Palmer amaranth, respectively, compared with 62% control with PRE-only programs 14 d after LPOST. Reductions in Palmer amaranth biomass followed the same trend; however, Palmer amaranth density was reduced 98% in EPOST fb LPOST programs compared to 91% reduction in PRE fb LPOST and 76% reduction in PRE-only programs. PRE fb LPOST and EPOST fb LPOST programs resulted in an average soybean yield of 4,478 and 4,706 kg ha−1, respectively, compared with 3,043 kg ha−1 in PRE-only programs. Herbicide programs evaluated in this study resulted in no soybean injury. The results of this research illustrate that herbicide programs are available for the management of GR Palmer amaranth in 2,4-D, glyphosate, and glufosinate-resistant soybean.

Control of acetolactate synthase inhibitor/glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in isoxaflutole/glufosinate/glyphosate-resistant soybean

“…Herbicides applied PRE fb glufosinate reduced MHR Palmer amaranth density by at least 87% in 2018 and 2019. Similar findings were reported by Shyam et al (2021) and Norsworthy et al (2016). Glufosinate applied alone reduced MHR Palmer amaranth density 89% and 58% in 2018 and 2019, respectively, whereas glufosinate mixed with isoxaflutole reduced density by 63% to 100% in 2018, and 85% to 94% in 2019 (Table 4).…”

“…Glufosinate mixed with isoxaflutole controlled Palmer amaranth 92% to 95% in 2018 and 85% to 94% in 2019 (Table 3). Shyam et al (2021) reported 88% Palmer amaranth control 14 DAEPOST with glufosinate. Conversely, found that glufosinate in single and sequential applications provided 53% to 76% and 56% to 77% waterhemp control, respectively.…”

Effect of row spacing and herbicide programs for control of glyphosate-resistant Palmer amaranth (Amaranthus palmeri) in dicamba/glyphosate-resistant soybean

“…Reduced control of Palmer amaranth with dicamba applied alone in 2019 can be attributed primarily to the shorter residual control by dicamba compared to other PRE herbicide programs evaluated as observed by Hedges et al (2019). Efficacy of premixed and tank-mixed PRE herbicides with multiple effective sites of action on Palmer amaranth control were previously evaluated in soybean fields in Nebraska, with Striegel et al (2020) and Shyam et al (2021) reporting 93% to 99% control 14 and 28 DAPRE. Results from the current study are similar to those reported by Meyer et al (2015), when flumioxazin/pyroxasulfone, metribuzin, dicamba, S-metolachlor, S-metolachlor/ fomesafen, acetochlor, isoxaflutole, and S-metolachlor/mesotrione applied PRE provided 95% to 99% control of Palmer amaranth 21 DAPRE in field experiments conducted in Arkansas, Illinois, Indiana, Missouri, Nebraska, and Tennessee.…”

Interference and management of herbicide-resistant crop volunteers

“…In a 2-yr study in Nebraska, Striegel et al (2020) reported that quizalofop can be applied for selective control of glyphosate/glufosinate-resistant volunteer corn in corn resistant to FOPs. Multiple HR soybean traits have been developed that enable use of phenoxy herbicides such as 2,4-D or dicamba in a mixture with glyphosate (Byker et al 2013;Shyam et al 2021). Growers prefer to mix 2,4-D or dicamba with ACCase inhibitors, assuming this mixture will provide broad-spectrum weed control; however, it can antagonize grass weed control (Blackshaw et al 2006;Underwood et al 2016).…”

“…Multiple HR crops have been developed and commercialized in recent years, including glyphosate/dicamba-or 2,4-D-resistant soybean and cotton, glyphosate/glufosinate-resistant corn, and 2,4-D/glufosinate/glyphosate-resistant corn primarily for control of GR weeds (Beckie et al 2019). Shyam et al (2021) reported herbicide programs for effective control of GR Palmer amaranth (Amaranthus palmeri S. Watson) in 2,4-D/glufosinate/glyphosate-resistant soybean. A few other studies reported greater control of GR weeds in multiple HR soybean (Byker et al 2013;Vink et al 2012;Yadav et al 2020).…”