Gramineous weeds have become increasingly problematic in field crops over the past decade, especially in crops without herbicide tolerance traits, making effective management of them more challenging. The objective of this study was to compare the efficacy of four very-long-chain fatty acid (VLCFA) elongase–inhibiting herbicides for preemergence control of two grass species, large crabgrass and Texas panicum, which produce seeds of different sizes. The results were consistent across locations and rating times. Applications of all evaluated herbicides resulted in >94% visible control of crabgrass, while control of Texas panicum ranged from just 50% to 87%. The greatest level of Texas panicum control occurred after applications of pyroxasulfone + carfentrazone, whereas all treatments demonstrated similar efficacy against large crabgrass compared with plants that served as nontreated controls. Visible weed control ratings aligned with normalized difference vegetation index readings collected from both unmanned aerial vehicles and a handheld GreenSeeker device, as well as with biomass measurements. Furthermore, stand counts of both weed species exhibited no significant differences among the herbicides. These findings indicate that the selectivity of herbicides that inhibit VLCFA elongase on grass species when applied preemergence may be attributable to differences in seed size.

Diflufenican is a selective phenyl ether, Group 12 herbicide. Limited information exists on the weed control efficacy of diflufenican and the potential improvement in weed control when it is co-applied with isoxaflutole. Three field studies were conducted in Ontario to evaluate preemergence applications of isoxaflutole and diflufenican alone and in combinations for weed control in corn. Isoxaflutole applied at 52.5, 79, and 105 g ai ha−1 provided effective control of velvetleaf (83% to 89%, 91% to 98%, and 92% to 97%), green pigweed (73% to 85%, 85% to 91%, and 94% to 97%), common ragweed (81% to 86%, 93% to 97%, and 95% to 97%), and common lambsquarters (88% to 89%, 96% to 99%, and 98% to 100%), respectively when evaluated at 2, 4, and 8 wk after treatment (WAT). Diflufenican applied alone at 75 to 150 g ai ha−1 provided ≤3% control of velvetleaf, ≤38% of green pigweed, ≤7% of common ragweed, and ≤20% of common lambsquarters. Isoxaflutole applied alone provided 16% to 75% control of barnyardgrass, while diflufenican was ineffective (<3%). The co-application of isoxaflutole + diflufenican improved control to 34% to 86%, with synergistic effects of barnyardgrass control observed at several rates. Isoxaflutole and diflufenican, applied alone controlled green foxtail by 15% to 72% and 0% to 12%, respectively. The co-application of isoxaflutole + diflufenican improved green foxtail control to 25% to 89% with synergistic responses at some rates and evaluation timings. There was minimal corn injury with these treatments. Weed interference reduced corn yield by up to 69%. Weed interference with diflufenican applied alone resulted in corn yields of 4570 to 4750 kg ha−1, which is similar to yields from the nontreated control (3.33 T ha−1). Reduced weed interference with isoxaflutole alone and in mixtures with diflufenican resulted in corn yields of 8.36 to 10.83 T ha−1, which is higher than yields from both the nontreated control plots and those that received diflufenican treatments. Overall, isoxaflutole provided consistent broadleaf weed control, while synergistic interactions with diflufenican enhanced barnyardgrass and green foxtail suppression.

Management of broadleaf weeds in chile pepper may be improved by including a rotation with sorghum treated with selective, non-residual herbicides. However, herbicides applied to sorghum specifically for managing weeds in subsequent chile pepper crops have not been evaluated. This study evaluated two herbicide treatments applied to sorghum for their effects on broadleaf weed density and hand hoeing time in chile pepper crops the following year, and compared the treatments for their net economic benefits across sorghum and chile pepper growing seasons. Treatments included 1) a sorghum nontreated control; 2) one herbicide application, which was a premix combination of 2,4-D (0.35 kg ai ha−1), bromoxynil (0.35 kg ai ha−1), and fluroxypyr (0.14 kg ai ha−1) applied at the 4-leaf stage of sorghum; 3) two herbicide applications, which included the aforementioned premix combination followed by bromoxynil (0.28 kg ai ha−1) applied at the 6-leaf stage of sorghum; and 4) weed-free sorghum using hand hoeing. Results indicated that broadleaf weeds covered less than 10% of the ground where sorghum had been treated with herbicides. The two-application treatment resulted in 24% fewer broadleaf weeds in chile pepper than in sorghum that had been hoed by hand, and 63% fewer than the one-application treatment. Hand hoeing time for chile pepper was similar among the two-application treatment, one-application treatment, and weed-free sorghum. A partial budget analysis indicated that the one-application treatment provided greater net economic benefit than the two-application treatment (US$6,550 ha−1 vs. US$5,894 ha−1), due to lower input costs and greater overall gross revenue. These findings indicate that a two-application treatment maximizes reductions of broadleaf weeds in chile pepper caused by rotational sorghum; however, the one-application treatment may be a cost-effective approach to reducing broadleaf weeds in chile pepper.

Smooth scouringrush is a deep-rooted, rhizomatous, herbaceous perennial that has been difficult to control in dryland wheat-producing regions in the Pacific Northwest. Long-term field experiments were conducted at Omak, Edwall, and Steptoe, Washington, to evaluate applications of chlorsulfuron + metsulfuron (21.9 + 4.4 g ai ha−1), triasulfuron (29.5 g ai ha−1), or MCPA ester (780 or 1,122 g ae ha−1). The Omak trial (2017–2021) included two 2-yr cycles of a winter wheat/chemical summer fallow rotation. The Edwall and Steptoe trials (2019–2025) included two 3-yr cycles of winter wheat/spring wheat/chemical summer fallow rotation. Six preassigned herbicide sequences tested the efficacy of 1) chlorsulfuron + metsulfuron applied during one or both chemical fallow phases and 2) triasulfuron alone applied to wheat. MCPA ester was applied as a check treatment. Smooth scouringrush stem density was evaluated in each plot each year. Chlorsulfuron + metsulfuron applied in the first chemical summer fallow phase maintained relatively low stem density in all three trials through the first rotation cycle compared with the check treatment. Chlorsulfuron + metsulfuron applied in the second chemical summer fallow phase extended control through the second rotation cycle. However, in the 3-yr rotation trials, chlorsulfuron + metsulfuron was not as effective in the second rotation cycle at Steptoe where stem densities averaged only 6 stems m−2 at time of the second application. Triasulfuron applied to wheat was not effective in controlling smooth scouringrush. Smooth scouringrush reduced wheat yield in the MCPA ester check sequence at Edwall, but no differences were observed at Steptoe or Omak. Chlorsulfuron + metsulfuron applied in chemical fallow is effective for long-term control of smooth scouringrush in wheat-based cropping systems. A subsequent application in chemical fallow can be effective if an adequate number of stems are present to facilitate foliar uptake.

Herbicides are commonly used for weed control in wheat production due to their effectiveness, speed, and lower cost compared to other management methods. This study aimed to evaluate the selectivity and efficacy of herbicides applied alone or in combination for controlling major weed species infesting wheat in Brazil. Field experiments were conducted in 2022 and 2023 using a randomized complete block design with four replications. Terbuthylazine (500 and 750 g ha−1) + adjuvant, carfentrazone-ethyl (120 g ha−1), saflufenacil and pyraflufen-ethyl (3.75 and 5 g ha−1) + clodinafop-propargyl caused the highest phytotoxicity to wheat. The best wheat physiological performance (internal CO2 concentration, photosynthesis and transpiration rates, stomatal conductance, water use, and carboxylation efficiencies) was observed with terbuthylazine (750 g ha−1), carfentrazone-ethyl (80 g ha−1), 2,4-D (670 g ha−1), and terbuthylazine + clodinafop-propargyl (750 + 96 g ha−1). Terbuthylazine (500 and 750 g ha−1) and pyraflufen-ethyl (3.75 and 5 g ha−1) combined with clodinafop-propargyl (96 g ha−1), provided the most effective control of wild radish and ryegrass and resulted in the highest grain yields. Regarding the grain yield components of wheat (number of plants per meter, number of spikes, spike length, number of filled and sterile grains, hectoliter weight, thousand-grain mass, and grain yield), the weed-free control and the treatment with terbuthylazine + clodinafop-propargyl (750 + 96 g ha⁻¹) showed the best performance. In the absence of weed control, average grain yield losses reached 91%. The herbicides terbuthylazine and pyraflufen-ethyl demonstrated potential for the control of broadleaf weeds such as wild radish, which exhibit resistance to acetolactate synthase inhibitors, and where 2,4-D is less effective under low-temperature conditions. However, further studies using commercial formulations, adjuvants, and varietal tolerance tests are required to validate the use of these herbicides on wheat in Brazil.

Acetyl-CoA carboxylase (ACCase)-inhibiting herbicides are primarily applied for controlling grass weeds in broadleaf crops. These herbicides are foliar-active, providing minimal residual weed control. This review aims to summarize 1) the history and use of ACCase-inhibiting herbicides in the United States; 2) ACCase-inhibitor-resistant weeds, their mechanisms of resistance, and management strategies; and 3) the future of ACCase-inhibiting herbicides. Herbicides that inhibit ACCase belong to three chemical families: aryloxyphenoxypropionates, cyclohexanediones, and phenylpyrazoles. They function by inhibiting the enzyme ACCase activity, thereby blocking the first step in de novo fatty acid biosynthesis and thus preventing the production of phospholipids and essential secondary metabolites in susceptible plants. Diclofop-methyl was the first ACCase inhibitor discovered in 1975, and commercialized in 1982 in the United States. Pinoxaden was the last herbicide to be commercialized in 2005. As of 2025, a total of 51 grass weed species have been documented as being resistant to ACCase-inhibiting herbicides worldwide, including 16 in the United States. The resistance in these weeds is attributed to both target-site and non–target site mechanisms. Mixing ACCase-inhibiting herbicides with auxinic herbicides can reduce grass weed control due to antagonistic interactions. Therefore, selecting an appropriate tank-mix partner with an ACCase inhibitor is crucial for achieving broad-spectrum weed control, or a dual-tank precision sprayer could be used. Clethodim is the most widely used ACCase-inhibiting herbicide, with 920,339 kg applied to approximately 16% of soybean crops planted in the United States in 2023, at an average application rate of 179 g ha‒1. A recent discovery, metproxybicyclone, will be the first carbocyclic aryl-dione herbicide from a new ACCase inhibitor family. This novel herbicide will be applied postemergence to control sensitive and ACCase inhibitor-resistant grass weeds in broadleaf crops. Continued research efforts are focused on discovering new ACCase-inhibiting herbicides capable of controlling ACCase inhibitor-resistant grass weeds.

Sugar beet with three-way resistance to dicamba, glufosinate, and glyphosate may provide sugar beet growers with additional herbicide options for management of glyphosate-resistant (GR) weed species such as Palmer amaranth and kochia. Field trials were conducted near Scottsbluff, Nebraska; Lingle, Wyoming; Kimberly, Idaho; and Ontario, Oregon in 2023, to compare the effectiveness of dicamba (549 g ae ha−1) + glyphosate (1,260 g ae ha−1) applied preemergence, and postemergence combinations of dicamba + glyphosate, glyphosate, and glufosinate (656 g ai ha−1) to manage weeds in sugar beet crops. Common lambsquarters, redroot pigweed, and GR kochia were present at the Idaho, Oregon, and Wyoming locations; and common lambsquarters and GR Palmer amaranth were present in Nebraska. Dicamba + glyphosate applied preemergence reduced common lambsquarters, redroot pigweed, and GR kochia compared with glyphosate applied alone. Common lambsquarters density was higher in plots where glufosinate had been applied early postemergence compared with dicamba + glyphosate and glyphosate applied alone. Glufosinate and dicamba + glyphosate applied early or late postemergence reduced GR Palmer amaranth density relative to glyphosate alone applied early or late postemergence. Postemergence applications had no significant effect on redroot pigweed or GR kochia density. Based on the findings of this research, sugar beet with three-way resistance to dicamba, glufosinate, and glyphosate will bring two additional sites of action to be used both preemergence and postemergence, providing improved weed control compared to currently available technology.

In the Midwest United States, early soybean planting is becoming more common, but the implications for soil residual herbicide dissipation and optimal application time remain unclear. Earlier planting extends the interval between soil-residual herbicide application at planting and the onset and peak of weed emergence, potentially reducing efficacy through an extended window for dissipation. This study aimed to evaluate the dissipation and weed control efficacy of soil residual herbicides applied at different timings in early planted soybean crops under varying soil conditions. At Arlington, Wisconsin, which has a silt loam soil, herbicide concentrations when soil was sampled, 21 d after the fourth and final application of herbicides, which followed a series of treatments from planting to the V1 growth stage of soybean, were similar across application times, whereas at Brooklyn, Wisconsin, which has a sandy loam soil, herbicide concentrations were usually higher when herbicides were applied later. Despite these differences, weed density at postemergence was similar across application times within each site. However, an additional late postemergence herbicide application was necessary at Brooklyn following the earliest application times in 2022, indicating more rapid herbicide dissipation. Herbicide dissipation and efficacy varied by soil texture. In sandy soils, early applications may lead to reduced control of late-emerging weeds due to rapid dissipation. In contrast, finer-textured soils may allow for more flexible application timing. These insights support site-specific residual herbicide application strategies in early planted soybean systems.