Efficacy of 2,4-D, Dicamba, Glufosinate and Glyphosate Combinations on Selected Broadleaf Weed Heights

Abstract

Palmer amaranth, sicklepod and pitted morningglory are the three most common and troublesome weeds in soybean in South Carolina. They exhibit very aggressive growth capabilities and if left uncontrolled in fields will cause significant reductions in soybean yields. Dicamba and 2,4-D herbicides are currently having a resurgence in usage due to the recent commercialization of soybean trait technologies with tolerance to these herbicides. Dicamba and 2,4-D when tank mixed with glufosinate and glyphosate may offer additional weed control to resistant weeds through the process of herbicide synergism. Greenhouse experiments were conducted in 2013 at Edisto Research and Education Center near Blackville, SC to evaluate the efficacy of glyphosate, glufosinate, dicamba and 2,4-D treatments alone and in combination on Palmer amaranth, sicklepod, and pitted morningglory at selected heights. Results suggested that glufosinate alone provided the overall best control for all 3 weed species. Glyphosate alone provided the lowest control of all 3 species at all heights. Synergism or improved sicklepod control was observed when glufosinate was tank mixed with dicamba. However, as sicklepod increased in height, glufosinate + 2,4-D or dicamba combination offered the best control compared to glufosinate alone (90% versus 86% in 20 cm plants and 87% versus 85% in 30 cm plant). In the 5 cm Palmer amaranth, decreased control was observed when glyphosate or glufosinate was tank mixed with 2,4-D. These experiments showed that glufosinate alone and/or in combination with 2,4-D or dicamba was the overall best treatment on the three broadleaf weed species.

Increased Absorption and Translocation Contribute to Improved Efficacy of Dicamba to Control Early Growth Stage Palmer amaranth (Amaranthus palmeri)

“…Similar to field observations, A. palmeri control declined on more fully developed plants at time of dicamba application as reported elsewhere (Hedges et al 2018;Joseph et al 2018). For example, increase in plant height from 5 cm to 10 cm and 30 cm at time of dicamba application resulted in a decline in A. palmeri control from 100% to 94% and 84%, respectively (Joseph et al 2018). Similarly, when either glyphosate or dicamba was applied on (to) 5-, 15-, and 25-cm-tall glyphosate-resistant horseweed (Erigeron canadensis L.), its control declined from 87% to 76% and 62%, respectively (Hedges et al 2018).…”

“…No experiment by treatment interaction was detected; therefore, data were combined across experiments. Similar to field observations, A. palmeri control declined on more fully developed plants at time of dicamba application as reported elsewhere (Hedges et al 2018;Joseph et al 2018). For example, increase in plant height from 5 cm to 10 cm and 30 cm at time of dicamba application resulted in a decline in A. palmeri control from 100% to 94% and 84%, respectively (Joseph et al 2018).…”

“…Increase in plant height at time of spraying from ≤10to 15-and 30-cm tall, however, reduced A. palmeri control from 25% to 0% and 99% to 42% and 30%, respectively, with an increase in dicamba dose from 70 to 560 g ha −1 (Figure 1). This reduction in control suggests that dicamba efficacy to control A. palmeri largely depend(s) on plant height at time of spraying (Hedges et al 2018;Joseph et al 2018). For instance, when the label-recommended dose of dicamba (560 g ha −1 ) was applied, 99% of ≤10-cm-tall A. palmeri control was achieved compared with only 42% and 30% of 15-and 30-cm-tall A. palmeri, respectively, which is less than the level of control (47%) achieved when only one-fourth of the label-recommended dose of dicamba was sprayed on ≤10-cm-tall A. palmeri (Figure 1).…”

Glufosinate‐ammonium: a review of the current state of knowledge

“…87 Tank-mixing glufosinate with 2,4-D or dicamba also provided additive or synergistic effect controlling glyphosate-resistant broadleaf weeds and might be largely adopted in transgenic glufosinate + dicamba and glufosinate +2,4-D resistant crops. 88 However, glufosinate mixtures with other herbicides have not always worked well. For example, glufosinate antagonized acetyl CoA carboxylase inhibitors for Eleusine indica control.…”

Physiological performance of glyphosate and imazamox mixtures on Amaranthus palmeri sensitive and resistant to glyphosate

“…The full comprehension of the physiology of individual and mixture herbicidal effects might enable knowledge-based adoption of alternative weed management practices in order to control the evolution of resistant weeds. Indeed, both synergism 43 and antagonism 44 have been described after mixing other herbicides. The close relationship between AAA and BCAA biosynthetic pathways and the common physiological effects provoked by EPSPS and AHAS-inhibitors (as they have been introduced above) makes interesting to study the physiological effects of their mixtures in plants.…”