Weed Control with Halauxifen-Methyl Applied Alone and in Mixtures with 2,4-D, Dicamba, and Glyphosate

Abstract

Synthetic auxin herbicides such as 2,4-D and dicamba are often utilized to control broadleaf weeds in preplant burndown applications to soybean. Halauxifen-methyl is a new synthetic auxin herbicide for broadleaf weed control in preplant burndown applications to corn, cotton, and soybean at low use rates (5 g ae ha–1). Field experiments were conducted to evaluate efficacy and weed control spectrum of halauxifen-methyl applied alone and in mixtures with 2,4-D (560 g ae ha–1), dicamba (280 g ae ha–1), and glyphosate (560 g ae ha–1). Glyphosate-resistant (GR) horseweed was controlled with halauxifen-methyl applied alone (90% control) and in mixtures (87% to 97% control) 35 d after treatment (DAT). Common ragweed was controlled 93% with halauxifen-methyl applied alone and 91% to 97% in mixtures 35 DAT. Halauxifen-methyl applied alone resulted in poor giant ragweed control 21 DAT (73% control); however, mixtures of halauxifen-methyl with 2,4-D, dicamba, or glyphosate controlled giant ragweed (86% to 98% control). Halauxifen-methyl alone resulted in poor redroot pigweed control (62% control) 21 DAT; however, mixtures of halauxifen-methyl with dicamba, 2,4-D, or glyphosate controlled redroot pigweed (89% to 98% control). Halauxifen-methyl controls GR horseweed and common ragweed applied alone and in mixtures with other synthetic auxin herbicides and glyphosate. Furthermore, mixing 2,4-D or dicamba with halauxifen-methyl can increase the weed control spectrum in preplant burndown applications.

Halauxifen-methyl controls glyphosate-resistant horseweed (Conyza canadensis) but not giant ragweed (Ambrosia trifida) in winter wheat

“…Furthermore, Kumar et al (2017) observed that fluroxypyr provided 83% to 88% control of GR horseweed 31 d after treatment (DAT), similar to the 89% control in this study. Previous research conducted by Zimmer et al (2018aZimmer et al ( , 2018b also found that halauxifen-methyl (5 g ai ha -1 ) provided 90% control of GR horseweed in soybean 35 DAT, comparable to the control observed in this study. In contrast, McCauley et al (2018) reported that halauxifen-methyl (5 g ha -1 ) provided 65% to 80% control of GR horseweed 28 DAT; their study was in a no-crop system, and plants ranged from 5 to 30 cm at application, whereas in this study all weeds were <10 cm tall, with crop competition, which may explain the lower control in that study.…”

“…Similar to this study, Mahoney et al (2016) reported that 2,4-D, clopyralid, fluroxypyr þ MCPA, and pyrasulfotole/bromoxynil reduced GR horseweed density by 94% to 99%. In contrast, Zimmer et al (2018a) reported that halauxifen-methyl applied in soybean reduced GR horseweed density by 76%.…”

Comparison of 2,4-D, dicamba and halauxifen-methyl alone or in combination with glyphosate for preplant weed control

“…These data from North Carolina and Virginia, in addition to research from Indiana (Zimmer et al 2018a(Zimmer et al , 2018b, indicate halauxifen-methyl effectively controls horseweed. In this experiment, halauxifen-methyl and dicamba controlled horseweed averaging 5 or 15 cm in height more effectively than did 2,4-D.…”

“…Other members of the pyridine-2-carboxylate family include picloram, clopyralid, and aminopyralid (Epp et al 2016). Halauxifen-methyl effectively controls horseweed at varying sizes (McCauley and Young 2016;Zimmer et al 2018a, Zimmer et. al 2018b.…”

“…al 2018b. Zimmer et al (2018aZimmer et al ( , 2018b reported halauxifen-methyl applied alone at 5 g ae ha −1 controlled GR horseweed 90%, and halauxifenmethyl in combinations with 2,4-D, dicamba, and/or glyphosate controlled GR horseweed 87% to 97%. In another study, dicamba and halauxifen-methyl applied alone provided 80% control of 30-cm horseweed, whereas 2,4-D applied at 560 g ae ha −1 controlled the weed less than 50% (McCauley and Young 2016).…”