Overlapping Residual Herbicides for Control of Photosystem (PS) II- and 4-Hydroxyphenylpyruvate Dioxygenase (HPPD)-Inhibitor-Resistant Palmer amaranth (Amaranthus palmeri S. Watson) in Glyphosate-Resistant Maize

Abstract

A Palmer amaranth (Amaranthus palmeri S. Watson) biotype has evolved resistance to photosystem (PS) II- (atrazine) and 4-hydroxyphenylpyruvate dioxygenase (HPPD)-inhibiting herbicides (mesotrione, tembotrione, and topramezone) in maize seed production field in Nebraska, USA. The objectives of this study were to determine the effect of soil residual pre-emergence (PRE) herbicides followed by (fb) tank-mixture of residual and foliar active post-emergence (POST) herbicides on PS-II- and HPPD-inhibitor-resistant Palmer amaranth control, maize yield, and net economic returns. Field experiments were conducted in a grower's field infested with PS II- and HPPD-inhibitor-resistant Palmer amaranth near Shickley in Fillmore County, Nebraska, USA in 2015 and 2016. The contrast analysis suggested that saflufenacil plus dimethenamid-P or pyroxasulfone plus saflufenacil applied PRE provided 80–82% Palmer amaranth control compared to 65 and 39% control with saflufenacil and pyroxasulfone applied alone at 3 weeks after PRE (WAPRE), respectively. Among the PRE fb POST herbicide programs, 95–98% Palmer amaranth control was achieved with pyroxasulfone plus safluefenacil, or saflufenacil plus dimethenamid-P applied PRE, fb glyphosate plus topramezone plus dimethenamid-P plus atrazine, glyphosate plus diflufenzopyr plus dicamba plus pyroxasulfone, glyphosate plus diflufenzopyr plus pendimethalin, or glyphosate plus diflufenzopyr plus dicamba plus atrazine applied POST at 3 weeks after POST (WAPOST) through maize harvest. Based on contrast analysis, PRE fb POST programs provided 77–83% Palmer amaranth control at 3 WAPOST through maize harvest compared to 12–15% control with PRE-only and 66–84% control with POST-only programs. Similarly, PRE fb POST programs provided 99% biomass reduction at 6 WAPOST compared to PRE-only (28%) and POST-only (87%) programs. PRE fb POST programs provided higher maize yield (13,617 kg ha−1) and net return (US $1,724 ha−1) compared to the PRE-only (2,656 kg ha−1; US $285 ha−1) and POST-only (11,429 kg ha−1; US $1,539 ha−1) programs. The results indicated that effective control of multiple herbicide-resistant Palmer amaranth can be achieved with PRE fb POST programs that include herbicides with overlapping residual activity to maintain season-long control.

Palmer Amaranth (Amaranthus palmeri) and Velvetleaf (Abutilon theophrasti) Control in No-Tillage Conventional (Non–genetically engineered) Soybean Using Overlapping Residual Herbicide Programs

“…Most of the PRE fb POST-WR programs resulted in ≥97% control of Palmer amaranth at 28 DAPOST. Similarly, Chahal et al (2018) reported that mixing soil-residual herbicides with foliar-active POST herbicides controlled HPPD and PSII inhibitor–resistant Palmer amaranth season-long in Nebraska. Averaged across programs, PRE-only herbicide programs reduced Palmer amaranth density by 67% at 28 DAPOST compared with the nontreated control (36 plants m −2 with PRE-only programs vs. 110 plants m −2 in nontreated control; Table 4).…”

“…Whitaker et al (2010) noted that PRE fb POST/POST-WR herbicide programs are necessary for effective management of Palmer amaranth and higher soybean yield. Moreover, Chahal et al (2018) showed that inclusion of soil-residual herbicides in POST treatments increased corn yield and net economic returns. Butts et al (2016) also reported that a PRE fb POST/POST-WR herbicide strategy is an important component in integrated weed management that can effectively manage Amaranthus spp.…”

“…In 2017, only 6% of soybean area in the United States was planted with non-GE soybean cultivars (USDA-NASS 2017). Palmer amaranth is the most problematic weed in conservation agriculture in the United States (Chahal et al 2015;Price et al 2011). A survey conducted by Sarangi and Jhala (2018) ranked Palmer amaranth and velvetleaf among the six most problematic weeds in Nebraska.…”

Integrated pigweed (Amaranthus spp.) management in glufosinate-resistant soybean with a cover crop, narrow row widths, row-crop cultivation, and herbicide program

“…Herbicide applications to manage difficult-to-control weeds should be implemented as part of a diverse integrated weed management program (Shaner 2014) and should contain multiple components, such as sequential applications of residual herbicides (Chahal et al 2018;Sarangi and Jhala 2018;Sosnoskie and Culpepper 2014;Steckel et al 2002). In addition, treatments should be planned that contain multiple effective sites of action for those species that are most likely to develop herbicide resistance (e.g., Palmer amaranth and waterhemp) as a best management practice (Norsworthy et al 2012).…”

Preemergence herbicide delays the critical time of weed removal in popcorn

“…Although PRE herbicides are important to corn production, they usually do not provide season-long control of certain weed species with wide emergence patterns, such as common waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] and Palmer amaranth (A. palmeri S. Watson) unless followed by a POST herbicide (Chahal et al 2018a(Chahal et al , 2018bNolte and Young 2002;Steckel et al 2002).…”