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.

Targeted herbicide applications have the potential to reduce herbicide use but they pose an inherent risk of missing late-season weed escapes. Furthermore, relying on targeted use of residual herbicides may increase weed emergence relative to broadcast applications. Research was conducted over a 3-yr period in Keiser, Arkansas, to compare traditional broadcast applications to targeted postemergence applications of various herbicides to soybean cultivars that are known to be resistant to glyphosate, glufosinate, and dicamba. The herbicide treatment protocol was consistent across treatments with a broadcast-applied preemergence residual, and a postemergence combination that included glufosinate + glyphosate + S-metolachlor followed by glufosinate + acetochlor, applied both via broadcast or targeted at the highest and lowest spray sensitivities of the John Deere See & Spray technology. The soil seedbank was similar at trial initiation across treatments, and there was no increase in the seedbank over 3 yr of broadcast and targeted applications at the highest spray sensitivity. Averaged over application timing, when herbicides were applied at the lowest spray sensitivity the weed density rose from 867 plants ha−1 to 2,870 plants ha−1 in Year 2, to 11,300 plants ha−1 in Year 3. This response is likely due to more Palmer amaranth escapes when the crop was harvested with an average of >1,000 plants ha−1 over the years compared with weed density after herbicides were applied with the highest spray sensitivity and via broadcast. Targeted applications improved profitability by reducing herbicide use and increasing application efficiency, providing an average savings of US$43.22 ha−1 to $129.19 ha−1 relative to broadcast postemergence cost of $227.22 ha−1. The area sprayed was reduced by 20% to 90%, with an average spraying at early postemergence of 41.3% and 57.9% and at mid-postemergence equaling 48.1% and 49.3% when herbicides were applied with the lowest and highest spray sensitivities, respectively. The only difference in the area sprayed between sensitivity settings occurred early postemergence. Based on the results of this experiment, producers could apply postemergence herbicides targeted to weeds that grow with soybean to increase profitability, but the lowest sensitivity resulted in unacceptable increases to the weed seedbank, which could affect management in future years.

Experiments in 2022 and 2023 at multiple locations in North Carolina aimed to identify alternative herbicide combinations that could provide effective preplant foliar weed control when glyphosate is unavailable. All combinations containing rimsulfuron + thifensulfuron provided 95% to 98% control of henbit, which is comparable to all glyphosate-based combinations. Treatments containing glyphosate achieved 100% control of common chickweed, and rimsulfuron + thifensulfuron combined with clethodim (90%) or 2,4-D (89%) were the only treatments that provided comparable control. Paraquat effectively controlled henbit and common chickweed, providing 91% and 87% control of these species, respectively. Although no treatment controlled annual bluegrass as effectively as glyphosate-based mixtures, paraquat alone, paraquat + 2,4-D, and clethodim + rimsulfuron + thifensulfuron each achieved ≥88% control. Saflufenacil was highly efficacious against purple cudweed, providing control that was comparable to that of glyphosate (≥97%). Tiafenacil applied alone provided limited control of most of the weed species evaluated, but showed compatibility in mixtures, suggesting it has utility within diversified preplant foliar herbicide programs targeting specific weeds. While glyphosate remains available for use, incorporating one or more of these herbicides could enhance control of glyphosate-resistant weed biotypes and reduce selection pressure on glyphosate-susceptible weeds. Overall, rimsulfuron + thifensulfuron, paraquat, saflufenacil, tiafenacil, and clethodim, applied alone or in combination, offer practical preplant foliar options that can strengthen existing glyphosate-based programs and sustain effective winter annual weed control should glyphosate become limited or unavailable.

The U.S. Environmental Protection Agency has proposed increased restrictions and lower application rates for atrazine. Corn growers need to have options for weed control, and increased scrutiny of atrazine may limit effective herbicides that inhibit the photosystem II within weeds. One alternative weed control option is the premixture of amicarbazone and metribuzin. The atrazine label prohibits planting soybean until the following year, limiting producers to replanting corn or grain sorghum after a failed stand. Amicarbazone allows a 4-mo soybean rotation interval, potentially enabling planting of the crop the same season as failed corn. Therefore, research was conducted in 2023 and 2024 in Fayetteville, Arkansas, to evaluate soybean tolerance to an amicarbazone and metribuzin premixture after a simulated failed corn stand. Amicarbazone was applied at 245, 490, and 735 g ai ha−1 alone and in combination with metribuzin at 140, 280, and 420 g ai ha−1. Soybean was planted following at least 1.3 cm of rain (19 to 20 d after application). The label allows amicarbazone and metribuzin to be applied to corn at 336 and 190 g ha−1, respectively, on silt loam soil with organic matter of 1.5% to 2%. The combination of amicarbazone and metribuzin at 735 and 420 g ha−1, respectively, more than twice the labeled rate for corn, induced 61% to 91% soybean injury 14 d after emergence (DAE). When amicarbazone and metribuzin rates were reduced to 245 and 140 g ha−1, respectively, the injury was 4% in both years at 14 DAE. Yield reductions were observed only after treatments with amicarbazone at 735 g ha−1 applied alone or in combination with metribuzin at 420 g ha−1. Overall, crop response and yield reductions should be expected with an amicarbazone and metribuzin premixture at the highest rates used in this study. However, the label for the premixture will not allow these rates to be applied.

Saflufenacil, a herbicide that inhibits protoporphyrinogen oxidase, has been reformulated as a microencapsulation for preemergence and postemergence applications to corn, with the primary purpose of the encapsulation to reduce the risk of corn injury from foliar applications. Field experiments on corn were conducted in 2023, 2024, and 2025 to evaluate the efficacy of encapsulated saflufenacil alone and in the formulated premixture with pyroxasulfone for residual broadleaf weed control and crop injury. Applications of encapsulated saflufenacil across a dose range resulted in incomplete control (less than 60%) of giant ragweed. Combinations of the encapsulated saflufenacil + pyroxasulfone premixture with atrazine were efficacious in controlling giant ragweed up to 28 d after planting (DAP), but efficacy declined sharply by 42 DAP. The reduced efficacy on giant ragweed was attributed to a lack of an activating rain for the encapsulated saflufenacil. Conversely, encapsulated saflufenacil applications, with or without pyroxasulfone, were highly efficacious (83% to 99% control) on waterhemp and common lambsquarters, two small-seeded broadleaf species. Furthermore, the most extensive weed control with encapsulated saflufenacil resulted from sequential applications (preemergence and postemergence) of a residual herbicide. Overall, encapsulated saflufenacil was effective in controlling small-seeded broadleaf weeds until a postemergence herbicide was applied. However, additional herbicides in a mixture may be needed to manage large-seeded broadleaf species such as giant ragweed. Regardless of the target species, management of problematic, herbicide-resistant weeds with encapsulated saflufenacil should focus on combinations with other effective herbicides in both preemergence and postemergence applications, in addition to other weed control tactics.

The use of unmanned aerial vehicles (UAVs) shows promise as a potential new way to apply herbicides; however, relatively few studies have been conducted to determine how UAV application parameters influence spray deposition and weed control. Separate experiments were conducted in soybean fields in 2023 and 2024 to 1) compare weed control, spray coverage, and uniformity, and off-target movement between a DJI Agras T40 unpiloted vehicle and ground-based sprayers; and 2) determine the effects of application speed, spray height, and spray volume on spray coverage and waterhemp control with a UAV. Ground-based sprayers consistently provided greater and more uniform spray coverage than the UAV and resulted in more consistent waterhemp control across the swath width. Normalized coverage data indicated greater proportional off-target spray movement with the UAV, although absolute off-target coverage did not differ between application methods. In the second experiment, a variety of different UAV spray application parameters were assessed for their effects on spray coverage and waterhemp control following applications of glufosinate. Coverage in the center of the swath was improved at an application speed of 3.5 m s−1 compared with 7 m s−1, while increasing the height of application above the soybean canopy from 3 m to 4.5 m resulted in lower waterhemp control. Overall, results from this research indicate that herbicides applied with a UAV can provide effective weed control under optimized operating conditions but generally require narrower swath widths, careful management of application parameters, and additional drift mitigation practices.

Widespread evolution of glyphosate resistance among kochia populations is a serious challenge for growers across the North American Great Plains. Dicamba has historically been used to control glyphosate-resistant (Gly-R) kochia. However, the increasing spread of dicamba-resistant kochia and current restrictions on the use of low-volatile formulations of dicamba warrant alternative herbicide options to control Gly-R kochia. In this context, field-based dose-response experiments were conducted in fallow in Hays, Kansas, during 2021 and 2022 to determine and compare the effectiveness of 2,4-D, dicamba, and dichlorprop-p applied alone, and in a premixture of 2,4-D/dicamba/dichlorprop-p for controlling Gly-R kochia. Averaged across 2 yr, results indicated that substantially lower doses of 2,4-D, dicamba, and dichlorprop-p were required in a premixture to achieve effective control of Gly-R kochia compared with their stand-alone applications. Specifically, the ED₉₀ values for Gly-R kochia control were reduced by 90, 4, and 6 times for 2,4-D, dicamba, and dichlorprop-p, respectively, when applied as a premixture. Similarly, achieving 90% biomass reduction required approximately 1,021, 3, and 4 times lower doses of 2,4-D, dicamba, and dichlorprop-p, respectively, in the premixture than when applied alone. Altogether, these results demonstrated that the premixture of 2,4-D/dicamba/dichlorprop-p can be an effective alternative for managing Gly-R kochia in fallow. The reduced dose requirements in a premixture also suggest potential benefits for resistance management, cost efficiency, and environmental stewardship.

Palmer amaranth has become one of the most problematic weeds in row crop production in states in the mid-South. With increasing resistance to multiple herbicides, new control methods are needed. Field experiments were conducted in 2024 and 2025 at four locations in Tennessee to evaluate the efficacy of dicamba and glufosinate applied alone, tank-mixed, or sequentially using a split-boom approach for controlling auxin herbicide-resistant Palmer amaranth populations. Control varied widely among populations, reflecting differences in dicamba resistance levels. Populations with low dicamba resistance treated with glufosinate showed 99% control following sequential applications, with no differences between tank-mix and split-boom methods. In contrast, populations with high dicamba resistance demonstrated reduced control across all treatments; however, the split-boom application improved initial control at one highly resistant site compared with the tank-mixed application. Sequential applications improved control at all locations compared with the initial application. Increasing the spray carrier volume from 140 to 280 L ha−1 did not improve control of Palmer amaranth. These results indicate that sequential applications of dicamba plus glufosinate are required to maximize control of auxin-resistant Palmer amaranth, but efficacy is population dependent, underscoring the need for crop scouting and integrated weed management strategies to mitigate resistance development to sustain herbicide effectiveness.