Reduced Translocation of Glyphosate and Dicamba in Combination Contributes to Poor Control of Kochia scoparia: Evidence of Herbicide Antagonism

Abstract

Kochia scoparia is a troublesome weed across the Great Plains of North America. Glyphosate and dicamba have been used for decades to control K. scoparia. Due to extensive selection, glyphosate- and dicamba-resistant (GDR) K. scoparia have evolved in the USA. Herbicide mixtures are routinely used to improve weed control. Herbicide interactions if result in an antagonistic effect can significantly affect the management of weeds, such as K. scoparia. To uncover the interaction of glyphosate and dicamba when applied in combination in K. scoparia management the efficacies of different doses of glyphosate plus dicamba were evaluated under greenhouse and field conditions using GDR and a known glyphosate- and dicamba-susceptible (GDS) K. scoparia. The results of greenhouse and field studies suggest that the combination of glyphosate and dicamba application controlled GDS, but glyphosate alone provided a better control of GDR K. scoparia compared to glyphosate plus dicamba combinations. Furthermore, investigation of the basis of this response suggested glyphosate and dicamba interact antagonistically and consequently, the translocation of both herbicides was significantly reduced resulting in poor control of K. scoparia. Therefore, a combination of glyphosate plus dicamba may not be a viable option to control GDR K. scoparia.

2,4-D antagonizes glyphosate in glyphosate-resistant barnyard grass <i>Echinochloa colona</i>

“…8,16) In addition, reduced glyphosate translocation by the auxin herbicide dicamba was recently reported in Kochia scoparia. 17) Here, a similar mechanism was observed in glyphosate-resistant barnyard grass (Table 2; Supplemental Fig. S1).…”

“…[2][3][4] However, synergism or antagonism can occur with certain herbicide mixtures. 2,5,6) Herbicide mixture synergism or antagonism can be due to altered herbicide uptake and/or translocation 5,[7][8][9][10][11][12][13][14][15][16][17] and metabolism. 5,[18][19][20] Both synergistic and an-tagonistic effects of 2,4-D (2,4-dichlorophenoxyacetic acid) and glyphosate [N-(phosphonomethyl) glycine] have been reported and are weed species specific.…”

Herbicide options for glyphosate-resistant kochia (Bassia scoparia) management in the Great Plains

“…For example, warmer temperatures can improve herbicide absorption and efficacy (Ganie et al 2017;Schultz and Burnside 1980). However, kochia control with glyphosate and dicamba can be reduced at elevated (32.5/22.5 C day/night) temperatures (Ou et al 2018 One of the challenges in weed management is dealing with the often-unpredictable variability caused by environmental or biological differences between sites. With the herbicide programs selected, those registered for corn and soybean demonstrated less variability in kochia control compared with fallow, wheat, and sugar beet (Figure 1).…”

“…Kochia is an invasive annual forb native to Asia, introduced into the United States at the end of the 1800s as an ornamental from Europe (Friesen et al 2009;Whitson et al 2000). Kochia is widespread throughout the northwestern United States, where it is found growing in grasslands, pastures, prairies, roadsides, ditch banks, wastelands, floodplains, riparian habitats, and cultivated fields (Casey 2009;Ou et al 2018;Stubbendieck et al 2003). Kochia was ranked among the most serious weed species in the northwest United States due to its high rate of spread (Forcella 1985).…”

Basis of Atrazine and Mesotrione Synergism for Controlling Atrazine‐ and HPPD Inhibitor‐Resistant Palmer Amaranth

“…At 4, 8, 24, 48, and 72 HAT, plants were dissected into treated leaf (TL), leaves above the treated leaf (ATL), leaves below the treated leaf (BTL), and the roots. Treated leaves were rinsed twice in a 20‐mL scintillation vial containing 5 mL of wash solution (10% v/v ethanol aqueous solution with 0.5% of Tween‐20) for 1 min to remove the unabsorbed herbicide from the surface of the treated leaf (Ganie et al, 2017b; Godar et al, 2015; Ou et al, 2018). The leaf rinse was mixed with 15 mL of scintillation cocktail [Ecolite‐( R ), MP Biomedicals, LLC, Santa Ana, CA], and radioactivity was determined by using liquid scintillation spectrometry (LSS) (Beckman Coulter LS6500 Multipurpose Scintillation Counter, Beckman Coulter, Inc., Brea, CA).…”