A new formulation of pyroxasulfone + encapsulated saflufenacil has been developed. Combining these two herbicides extends the application window to early postemergence. Pyroxasulfone, saflufenacil (suspension concentrate), and pyroxasulfone + encapsulated saflufenacil (microcapsule suspension) were applied to corn preemergence and evaluated for corn injury, corn yield, and visible weed control; in addition, the interaction (antagonistic, additive, or synergistic) was ascertained for each parameter. Six field trials were conducted at three locations in southwestern Ontario in 2022 and 2023. Pyroxasulfone was applied at 90, 120, and 150 g ai ha−1; saflufenacil was applied at 56, 75, and 95 g ai ha−1; and pyroxasulfone + encapsulated saflufenacil was applied at 146, 195, 245 g ai ha−1, equal to the combined rates of pyroxasulfone and saflufenacil. All pyroxasulfone, encapsulated saflufenacil, and pyroxasulfone + encapsulated saflufenacil treatments caused no corn injury. Weed control varied based on application rate and weed species. Reduced weed interference with pyroxasulfone + encapsulated saflufenacil at 195 and 245 g ai ha−1 resulted in corn yield that was similar to the weed-free control and the industry standard of S-metolachlor/atrazine/mesotrione/bicyclopyrone. The interaction between pyroxasulfone and encapsulated saflufenacil for weed control was additive.

Smooth scouringrush is an herbaceous perennial with an extensive underground rhizome system that has invaded no-till dryland production fields in the inland Pacific Northwest. The objective of this field study was to determine whether there were any short- or long-term benefits to tank-mixing chlorsulfuron + metsulfuron with glyphosate for smooth scouringrush control. Field studies were conducted at three sites across eastern Washington from 2020 to 2024. Glyphosate was applied during fallow periods at 0, 1,260, 2,520, and 3,780 g ae ha−1 with and without chlorsulfuron + metsulfuron applied at 21.9 + 4.4 g ai ha−1. Smooth scouringrush stem density was evaluated 1, 2, and 3 yr after treatment. Chlorsulfuron + metsulfuron provided excellent control of smooth scouringrush (<5 plants m−2) for the first 2 yr at all three sites, and there was no observed benefit of tank-mixing with glyphosate. This continued to be the case 3 yr after treatment at two of the sites, but at one site, adding glyphosate at 2,520 or 3,780 g ha−1 to chlorsulfuron + metsulfuron decreased stem density compared to chlorsulfuron + metsulfuron applied alone. For treatments containing glyphosate only, the greatest efficacy 3 yr after treatment was achieved at the highest application rate of 3,780 g ha−1. Although no short-term benefit was observed in adding glyphosate to chlorsulfuron + metsulfuron for smooth scouringrush control, at one of three sites the duration of control was increased by at least 1 yr with the addition of glyphosate at a rate of 2,520 g ha−1 or more and an organosilicone surfactant as tank-mix partners.

Geyer larkspur is a native perennial forb toxic to cattle. Herbicide control of Geyer larkspur is variable and most likely attributable to the growth stage of the plant when herbicide is applied. The objectives of this study were to (1) evaluate aminopyralid, aminopyralid + florpyrauxifen-benzyl, aminopyralid + 2,4-D, aminopyralid + metsulfuron-methyl, metsulfuron-methyl, triclopyr, and triclopyr + 2,4-D for efficacy in controlling Geyer larkspur; (2) determine if plant growth stage (vegetative or flowering) at the time of herbicide application influences herbicide effectiveness; and (3) determine whether herbicide treatment alters norditerpenoid alkaloid content of Geyer larkspur. Plots were established in eastern Wyoming (2021) and northern Colorado (2022). Herbicide application at the different phenological stages did not affect Geyer larkspur density at the Wyoming site (P = 0.1065; data not shown). Geyer larkspur density at the Wyoming site was reduced by all herbicide treatments 1 year after treatment (YAT) at the vegetative stage and by all herbicides except for triclopyr 2 YAT (P = 0.0249). At the flowering stage, Geyer larkspur density was reduced by all herbicides except metsulfuron-methyl, triclopyr, and triclopyr + 2,4-D at 1 YAT and triclopyr and triclopyr + 2,4-D at 2 YAT. In contrast, there were no differences in Geyer larkspur density across treatments at the Colorado site (P = 0.9621). Precipitation was below average several months prior to herbicide application, which may have affected herbicide effectiveness. The metsulfuron-methyl treatment resulted in the highest total alkaloid concentrations of Geyer larkspur at the vegetative stage and the lowest concentrations at the flowering stage at the Wyoming site. Control efforts of Geyer larkspur in semiarid rangelands can be effectively accomplished with aminopyralid herbicides across vegetative and flowering growth stages provided environmental conditions prior to herbicide application are sufficient for plant growth and uptake of the herbicide.

New technologies in grain sorghum allow for the use of multiple acetyl CoA carboxylase- (ACCase) or acetolactate synthase- (ALS) inhibiting herbicides for johnsongrass control. With the growing issue of herbicide resistance, producers need to understand which herbicides will successfully control johnsongrass accessions. To determine the efficacy of herbicides recently registered or ones with potential to become available for use in grain sorghum, johnsongrass seeds were collected from 2017 to 2021 in Arkansas, Kansas, Texas, and Oklahoma and were screened for sensitivity to fluazifop, quizalofop, nicosulfuron, and imazamox. Additionally, glyphosate sensitivity was evaluated because of its use before planting or postharvest. Quizalofop resulted in 100% mortality of all johnsongrass accessions. Of the johnsongrass accessions evaluated, 89% were completely controlled with glyphosate. The ALS inhibitors nicosulfuron and imazamox resulted in 100% mortality of all Oklahoma accessions, but failures occurred on samples from other states. One accession from Kansas, 12 from Texas, and eight from Arkansas were found to have reduced sensitivity to nicosulfuron and imazamox. If producers plan to plant grain sorghum in areas with johnsongrass populations, an ACCase-inhibitor herbicide will most likely provide effective control. Imazamox and nicosulfuron, in conjunction with the appropriate trait, can be utilized in areas with sensitive johnsongrass populations or where other sensitive grass species are present.