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

Abstract

Horseweed is a competitive summer or winter annual weed that produces up to 230,000 small seeds per plant that are capable of traveling more than 500 km via wind. Giant ragweed is a tall, highly competitive summer annual weed. Glyphosate-resistant (GR) horseweed and GR giant ragweed pose significant challenges for producers in the United States and Ontario, Canada. It is thought that an integrated weed management (IWM) system involving herbicide rotation is required to control GR biotypes. Halauxifen-methyl is a new selective broadleaf POST herbicide registered for use in cereal crops; there is limited information on its efficacy on horseweed and giant ragweed. The purpose of this research was to determine the efficacy of halauxifen-methyl applied POST, alone and in a tank mix, for the control of GR horseweed and GR giant ragweed in wheat across southwestern Ontario. For each weed species, an efficacy study consisting of six field experiments was conducted over a 2-yr period (2018, 2019). At 8 wk after application (WAA), halauxifen-methyl, fluroxypyr/halauxifen-methyl, fluroxypyr/halauxifen-methyl + MCPA EHE, fluroxypyr + MCPA ester, 2,4-D ester, clopyralid, and pyrasulfotole/bromoxynil + ammonium sulfate controlled GR horseweed >95%. Fluroxypyr and MCPA provided only 86% and 37% control of GR horseweed, respectively. At 8 WAA, fluroxypyr, fluroxypyr/halauxifen-methyl, fluroxypyr/halauxifen-methyl + MCPA EHE, fluroxypyr + MCPA ester, fluroxypyr/halauxifen-methyl + MCPA EHE + pyroxsulam, 2,4-D ester, clopyralid, and thifensulfuron/tribenuron + fluroxypyr + MCPA ester controlled GR giant ragweed 87%, 88%, 90%, 94%, 96%, 96%, 98%, and 93%, respectively. Halauxifen-methyl and pyroxsulam provided only 45% and 28% control of GR giant ragweed, respectively. Halauxifen-methyl applied alone POST in the spring controlled GR horseweed but not GR giant ragweed in winter wheat.

Control of Multiple-Herbicide-Resistant Canada Fleabane With Fall, Spring, and Sequential Herbicide Applications in Winter Wheat

“…At 1 and 4 WAA and 1 and 4 WAB there was no visible winter wheat injury from any of the herbicide treatments evaluated (data not presented). These results are similar to other studies that have shown minimal injury in winter wheat with herbicide applications that included pyrasulfotole, bromoxynil, fluroxypyr, halauxifen, and MCPA (Mahoney et al, 2016;McNaughton et al, 2014;Reddy et al, 2012;Robinson et al, 2015;Soltani et al, 2006Soltani et al, , 2020Quinn et al, 2020).…”

“…The results of this are similar to other studies in which pyrasulfotole/bromoxynil, halauxifen, fluroxypyr/halauxifen + MCPA, pyrasulfotole/bromoxynil/fluroxypyr, pyrasulfotole/bromoxynil/thiencarbazone, pyrasulfotole/bromoxynil/thiencarbazone + MCPA, and fluroxypyr/halauxifen + pyroxsulam + MCPA controlled GR Canada fleabane 94-100% in winter wheat (Soltani et al, 2020). Quinn et al (2020) reported that GR Canada fleabane was controlled 91-98% with pyrasulfotole/bromoxynil, 83-97% with fluroxypyr/halauxifen + MCPA, and 86-97% with clopyralid applied in the spring. In another study, GR Canada fleabane was controlled 54-60% with bromoxynil + MCPA, 82-87% with fluroxypyr + MCPA, 95-97% with pyrasulfotole/bromoxynil, and 86-96% with clopyralid in winter wheat (Mahoney et al, 2016).…”

Hairy buttercup (Ranunculus sardous) and cutleaf evening primrose (Oenothera laciniata) control using halauxifen-methyl based programs in Mississippi and Oklahoma winter wheat

“…Halauxifen plus florasulam resulted in similar control to the best-performing herbicide treatments for hairy buttercup control. These results were also observed in other studies assessing control of halauxifen plus florasulam for horseweed control (Crose et al 2020;McCauley et al 2018;Quinn et al 2020) and control of other annual broadleaf weeds (Love et al 2016;Zimmer et al 2018). For cutleaf evening primrose control, our preliminary results suggest that using chlorsulfuron plus metsulfuron is highly effective, though overuse of ALS herbicides will increase the likelihood of herbicide-resistance development in cutleaf evening primrose, which has yet to be documented.…”

“…Halauxifen-methyl provided effective control of nine broadleaf weed species, with a shorter soil half-life compared with other screened herbicides, which led to the commercialization of this herbicide active ingredient (Schmitzer et al 2015). Halauxifen-methyl is effective at controlling horseweed (Crose et al 2020;McCauley et al 2018;Quinn et al 2020), but little research has been published on control of other winter broadleaf weeds like hairy buttercup or cutleaf evening primrose. The objective of the present study was to assess the effectiveness of halauxifen-methyl plus florasulam herbicide programs to control hairy buttercup and cutleaf evening primrose in Mississippi and Oklahoma.…”

Glyphosate-Resistant Canada Fleabane Control in Winter Wheat with Postemergence Herbicides

“…Weeds such as GR Canada fleabane competes with winter wheat for light, water, space, and nutrients and can cause significant yield losses in winter wheat [7]. Quinn et al [8] found a 13% numeric yield decrease due to GR Canada fleabane interference in winter wheat. e discovery of GR weeds in Ontario has provided a market opportunity for various agri-chemical companies that have herbicides with activity on these GR biotypes as they may provide an efficacious, cost-effective weed management solution for the control of these yield robbing weed biotypes.…”