Abstract
A study was conducted for three seasons in northwest Kansas, USA to evaluate acetolactate synthase (ALS)-inhibiting herbicides for downy brome (Bromus tectorum L.) and winter annual broadleaf weed control in winter wheat. Herbicides included pyroxsulam at 18.4 g ai ha−1, propoxycarbazone-Na at 44 g ai ha−1, premixed propoxycarbazone-Na & mesosulfuron-methyl at 27 g ai ha−1, and sulfosulfuron at 35 g ai ha−1. The herbicides were applied postemergence in fall and spring seasons. Averaged over time of application, no herbicide controlled downy brome more than 78% in any year. When downy brome densities were high, control was less than 60%. Pyroxsulam controlled downy brome greater than or similar to other herbicides tested. Flixweed (Descurainia sophia L.), blue mustard [Chorispora tenella (Pallas) DC.], and henbit (Lamium amplexicaule L.) control did not differ among herbicide treatments. All herbicides tested controlled flixweed and blue mustard at least 87% and 94%, respectively. However, none of the herbicides controlled henbit more than 73%. Fall herbicide applications improved weed control compared to early spring applications; improvement ranged from 3% to 31% depending on the weed species. Henbit control was greatly decreased by delaying herbicide applications until spring compared to fall applications (49% vs. 80% control). Herbicide injury was observed in only two instances. The injury was ≤13% with no difference between herbicides and the injury did not impact final plant height or grain yield.
Highlights
Wheat (Triticum aestivum L.) is the most important cereal grain crop in the USA, where it was planted on 23 million ha in 2012 [1]
Common broadleaf weeds found in winter wheat growing regions of the central U.S include blue mustard [Chorispora tenella (Pallas) DC.], henbit (Lamium amplexicaule L.), flixweed [Descurainia sophia (L.) Webb
Year-by-herbicide interaction was significant for downy brome and flixweed
Summary
Wheat (Triticum aestivum L.) is the most important cereal grain crop in the USA, where it was planted on 23 million ha in 2012 [1]. Winter annual grasses in wheat typically are more difficult to control than broadleaf weeds. Acetolactate synthase (ALS)-inhibiting herbicides have been primary herbicides for broadleaf weed control in winter wheat for more than three decades and for winter annual grass control for nearly two decades. Chlorsulfuron, metsulfuron, thifensulfuron, triasulfuron and tribenuron are registered for weed control in wheat These herbicides provide good broadleaf weed control efficacy, but have little or no activity on brome species (Bromus spp.) [11]. Was the first herbicide registered primarily to control winter annual grasses in wheat [11]. The objectives of this study were (1) to compare weed control efficacy of sulfosulfuron, propoxycarbazone-Na, propoxycarbazone-Na plus mesosulfuron, and pyroxsulam in winter wheat and (2) to determine the effect of herbicide application timing on weed control
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