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 dicamba use (low volatile formulations) warrant alternative herbicide options to control Gly-R kochia. In this context, field-based dose response experiments were conducted in fallow at Kansas State University Agricultural Research Center, Hays, KS, 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 two years, 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 standalone 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 1021-, 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 suggested potential benefits for resistance management, cost efficiency, and environmental stewardship.

Knotroot foxtail is a troublesome perennial grass found in pastures across the Southeastern United States. Herbicides such as hexazinone and quinclorac are labeled for control of this weed; however, their efficacy can be inconsistent due to delayed or excessive rainfall, which limits herbicide movement into the soil for root uptake, allowing knotroot foxtail rhizomes to survive and produce new shoots, resulting in reduced control. A greenhouse study was conducted at Auburn University, Alabama, in 2023 and 2024 to evaluate the effect of rainfall timing on the efficacy of quinclorac and hexazinone in controlling knotroot foxtail. Knotroot foxtail plants averaging 28 cm in height were treated with quinclorac (0.4 kg ae ha-1) or hexazinone (0.8 kg ai ha-1), followed by simulated rainfall (6.3 mm) applied at 0, 3, 6, 9, 12, and 15 days after herbicide treatment. Hexazinone provided greater knotroot foxtail control and rhizome biomass reduction than quinclorac. At 51 days after each rainfall treatment (DAERT), hexazinone provided 90% control, compared with 76% with quinclorac. In 2024, at 51 DAERT, control with hexazinone ranged from 99% to 92% when rainfall occurred within 0 to 6 days after application, but declined to 85% and 81% when rainfall was delayed until 12 and 15 days, respectively. Similarly, quinclorac-treated plants achieved 87% to 77% control when rainfall occurred within 0 to 9 days, but control dropped to 67% to 62% with delayed rainfall at 12 to 15 days. Relative to the nontreated control, hexazinone and quinclorac reduced knotroot foxtail rhizome biomass by 72% and 42%, respectively. Early rainfall (0 to 6 days) after herbicide application enhanced knotroot foxtail control, while delayed rainfall reduced herbicide effectiveness. This study underscores the importance of the timing of application when hexazinone or quinclorac is used for knotroot foxtail management before precipitation events.

Early-season crop yield loss frequently occurs even when resources are abundant, challenging traditional resource-based models of crop–weed competition. Drawing on decades of research on the critical period for weed control, this review highlights evidence that brief exposure of crop seedlings to neighboring weeds can trigger rapid and irreversible reductions in yield potential through resource-independent mechanisms. Central to these processes are weed-induced changes in light spectral quality, particularly reduced red:far-red (R:FR) ratios, which activate the phytochrome-mediated shade avoidance syndrome (SAS). These responses alter morphology, biomass allocation, canopy architecture, photosynthetic capacity, redox homeostasis, defense signaling, and nitrogen metabolism. Low R:FR light induces persistent photosynthetic and metabolic constraints, increases reactive oxygen species (ROS) signaling, suppresses jasmonic acid- and salicylic acid-mediated defenses, and modifies nitrate assimilation and root traits in species- and genotype-dependent manners. Collectively, weed-derived signals during early crop development can lead to lasting physiological reprogramming. Integrating light-mediated signaling with metabolic, defense, epigenetic, and lncRNA-mediated pathways provides a mechanistic framework for understanding yield loss and identifies potential targets for enhancing crop competitiveness and resilience in weed-infested agroecosystems.

Alligatorweed, an invasive aquatic weed, has emerged as a major threat to sustainable crop production in various crop species. A two-year field study was conducted to investigate the impact of varied competition durations of alligatorweed on mungbean. The competition durations with alligatorweed included weed free conditions for first 3, 4, 5, 6 and 7 weeks after crop emergence along with a full season weed free treatment and alternatively weedy conditions for the aforementioned durations along with a full season weedy treatment. Competition with alligatorweed led to significant uptake of nitrogen (N), phosphorus (P) and potassium (K), with maximum uptake observed in the full season weedy treatment with N, P and K up to 65, 19, 56 kg ha-1, respectively. Additionally, significant accumulation of heavy metals (HMs) including copper (Cu), iron (Fe), manganese (Mn), zinc (Zn) and arsenic (As) up to 20, 16, 30, 14 and 11 g ha-1, respectively, was observed. Full season weedy plots produced more alligatorweed biomass and caused reductions of up to 81% in mungbean yield components. Alligatorweed infestation resulted in significant mungbean grain yield losses of up to 44% during 2022 and 52% in 2023, respectively. Furthermore, the three-parameter log-logistic equations identified the period from 4.2 to 6.8 weeks after crop emergence (WACE) as the critical period of alligatorweed competition that could result in a 10% yield loss in mungbean. Hence, alligatorweed poses a significant threat to mungbean production due to its strong competitive ability. However, its potential for HM accumulation offers promising opportunities for phytoremediation in both aquatic and terrestrial environments.

Precision applications are gaining interest as a sustainable approach to managing turfgrass pests. For instance, controlling turfgrass weeds with precision application could effectively reduce herbicide volume without sacrificing weed control. Machine learning models have been a common method for precision application, but machine learning requires intensive labor and expertise to collect and label imagery. The objective of this study was to develop and test a new system utilizing the Dark Green Color Index (DGCI) for precision application of glyphosate to detect and spray winter weeds in dormant bermudagrass systems. For this study, a sprayer prototype was constructed that utilized machine vision and DGCI. The prototype consisted of three primary components: 1) a camera that streamed video frames, 2) a control system that stored computer code focused on the integration of DGCI, and 3) solenoid valves that activated upon detection of winter weeds in dormant bermudagrass. Four field trials with different weed species and weed densities were established to test the DGCI system amongst traditional application methods (i.e., broadcast application and manual spot application with a backpack sprayer). In the lowest weed-density scenario, the DGCI system accurately detected and sprayed 90% of the weed population, reducing herbicide volume by 62% compared to a broadcast application. Additionally, the DGCI system required less time for treatment than the spot application with a backpack sprayer. The results from these trials suggest that vegetative indices, such as DGCI, have potential in dormant bermudagrass systems to optimize herbicide volume.

The use of unmanned aerial vehicles (UAVs) shows promise as a potential new method of herbicide application; 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 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 to 7 m s-1, while increasing the height of application above the soybean canopy from 3 to 4.5 m resulted in lower waterhemp control. Overall, results from this research indicate that UAV applications can provide effective weed control under optimized operating conditions but would require narrower swath widths, careful management of application parameters, and additional drift mitigation practices.

Saflufenacil, a protoporphyrinogen oxidase (PPO)-inhibiting herbicide, has been reformulated as a microencapsulation for preemergence and postemergence applications in 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 days after planting (DAP), but efficacy declined sharply by 42 DAP. The reduced efficacy on giant ragweed was attributed to a lack of activating rainfall for the encapsulated saflufenacil. Conversely, encapsulated saflufenacil applications, with or without pyroxasulfone, were highly efficacious (83 to 99% control) on the small-seeded broadleaf species waterhemp and common lambsquarters. Furthermore, the most extensive weed control with encapsulated saflufenacil resulted from sequential applications (PRE/POST) of residual herbicide. Overall, encapsulated saflufenacil was effective in controlling small-seeded broadleaf weeds until a POST application was performed. 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 PRE and POST applications, in addition to other weed control tactics.

Green kyllinga is a perennial sedge that forms dark green mats that can hinder production activities in specialty crop fields. Seeds of this species are highly viable, and seed dispersal can cause rapid increases in population density. In addition, new shoots are produced from each stem node of the underground rhizomes. Green kyllinga is primarily a weed of turf; however, it has increasingly been observed in the row middles (space between raised beds) in Florida small fruit and vegetable crop fields. Trials were conducted to identify the most effective herbicide options from active ingredients registered for use in row middles. Lactofen PRE (404 g ai ha-1) was the most effective at controlling green kyllinga emergence followed by pendimethalin (868 g ai ha-1). Glufosinate at rates of 189, 378, and 755 g ai ha-1 caused 75 to 93% control on 1 cm tall vegetative green kyllinga shoots. Glufosinate applied at rates of 378 and 755 g ai ha -1, delivered 96 and 100% control, respectively, on 9 cm tall vegetative shoots. Glufosinate was less effective on flowering green kyllinga, with >90% control only achieved at rates of 755 g ai ha-1. Shoot dry weight following glufosinate applications did not consistently decrease at the flowering stage until the highest glufosinate rate was applied. We conclude that PRE applications of lactofen or pendimethalin followed by POST applications of glufosinate prior to flowering are effective management options for green kyllinga.

The 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 photosystem II-inhibiting herbicides. One alternative 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 four-month 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, AR, 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 rainfall, (19-20 days 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 at 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 days 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, 14 DAE. Yield reductions were only seen in 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.

Advancements in precision agriculture have driven the development of spray drones for herbicide application, offering the potential to address challenges associated with current application methods and improve weed management. This review synthesizes current research on spray drones to develop broad-use recommendations and identify challenges and knowledge gaps. Although spray drones use lower carrier volumes than ground-based sprayers (high-volume backpack or tractor-mounted sprayers), studies report comparable or superior weed control as well as herbicide cost savings. However, spray drone performance is highly sensitive to operational parameters, as spray distribution and coverage/deposition are strongly affected by flight height and speed, carrier volume, nozzle design, crop growth stage, weed, and weather conditions. The bell-shaped curve of a single-pass spray pattern, which results in most spray deposition occurring directly under the unmanned aerial vehicle (UAV), coupled with advances in imaging, remote sensing, and machine learning, demonstrate the strong potential of spray drones for site-specific weed management. Vegetation indices, multispectral imagery, canopy height models, and Light Detection And Ranging (LiDAR) technology have enabled crop-weed discrimination, though accuracy varies with species, growth stage, and image resolution. Deep-learning models such as ‘You Only Look Once’ (YOLO), Residual Neural Network (ResNet) and Mask Region-based Convolutional Neural Network (Mask R-CNN) achieve high performance for weed detection and/or segmentation but remain limited by training data quality and reduced accuracy with small, overlapping, or dense weed populations. Spray drone-based offline mapping has enabled substantial herbicide savings by delineating weed patches, whereas real-time weed detection is constrained by onboard processing limits, battery life, and lower spatial resolution at operational flight heights. Ground-based smart sprayers offer higher real-time detection precision but lack the field accessibility advantages of spray drones. Despite their potential, spray drones face challenges, including limited payload, off-target movement of pesticides, short battery life, regulatory challenges, and extensive license and complex software and calibration requirements. The downwind spray drift potential of spray drones is greater than ground applications but smaller than manned aerial applications. An upwind swath offset is an ideal best management practice to reduce off-target pesticide movement to susceptible areas from both manned and spray drone equipment. Future research should evaluate spray drones within integrated weed management systems, focusing on preemergence and foliar-applied contact herbicides, adjuvant use, environmental and operational interactions to develop spray drone-specific guidelines and optimize spray performance.

Silverleaf nightshade, a highly invasive perennial weed, poses a serious threat to crops and orchards in Mediterranean regions. This weed reproduces both sexually, through seeds, and asexually, via an extensive rhizome network, contributing to its persistence and spread. Managing silverleaf nightshade is particularly challenging, requiring integrated chemical and non-chemical approaches. This study evaluated the effectiveness of preemergence and postemergence herbicides and thermal control methods at three growth stages (2-3, 4-6, and 7-10 true-leaf stages [TL]) of silverleaf nightshade. Seven preemergence herbicides were tested in a dose-response experiment at rates between 0.0625X and 2X of the recommended label rate on seedling emergence from three populations. Metribuzin, pyroxasulfone, pendimethalin, and sulfosulfuron suppressed seedling emergence by 80-90% at 28 days after treatment. Seven postemergence herbicides were tested on the same three seed populations, and on plants grown from rhizomes. Treatments were applied at three rates: the recommended label rate (1X) and two exploratory rates 0.5X and 2X. At the 1X and 2X rates, aminopyralid and glufosinate reduced biomass by more than 90% at all growth stages. Fluroxypyr and imazapic reduced biomass by more than 95% at the 2-3 TL growth stage across all application rates. At the 4-6 and 7-10 TL growth stages, biomass reduction >90% was achieved only at the 2X rate. Propane flaming at 33.3, 50 and 100 kg ha⁻¹ and electrocution with 18, 45 and 90 J (correspond to 0.5X, 1X and 2X application rates) tested across the three growth stages. Both thermal methods were highly effective at the 2-3 TL stage, reduced biomass >95%. The results highlight the importance of early intervention, as both herbicide and thermal treatments efficacy declined significantly as the weeds matured. Integrating pre and postemergence herbicides with thermal treatment could improve the long-term management of silverleaf nightshade in Mediterranean cropping systems.

Drill-seeded rice (DSR) offers several agronomic and environmental advantages over conventional puddled transplanted rice (PTR), including labor and water savings, reduced cultivation costs, and lower greenhouse gas emissions. Despite these benefits, weed control remains a major bottleneck in the widespread adoption of DSR. Imidazolinone-resistant rice (IMI-rice), which allows the use of imidazolinone herbicides, has the potential to overcome weed control challenges in DSR and can therefore facilitate the transition from PTR to DSR. However, limited information exists on the effectiveness of IMI herbicide-based weed control programs in drill-seeded IMI-rice in northwestern India. Field experiments were conducted in Karnal, India, from 2020 through 2023 growing seasons to (1) evaluate the timing and rates of IMI herbicides for effective weed control in IMI-rice under DSR conditions, and (2) assess the potential carryover effects of IMI herbicides on succeeding crops. Results showed that sequential postemergence (POST) applications of imazethapyr—early-POST followed by (fb) late-POST at either 100 fb 150 or 125 fb 125 g ai ha-1 effectively reduced biomass by 83 to 100% for key weed species, including barnyardgrass, crowfootgrass, and Chinese sprangletop, compared to weedy check, and provided yields similar to weed-free treatment. These sequential POST treatments were consistently more effective than conventional herbicide program of oxadiargyl as preemergence (PRE) fb bispyribac-sodium as POST. Sequentially PRE fb POST applications of imazethapyr were relatively less effective in controlling weeds and minimizing yield losses compared to sequential POST applications. However, in the second and third years, oxadiargyl 90 g ai ha-1 as PRE fb imazethapyr 100 g ai ha-1 as POST achieved comparable weed control efficiency to the sequential POST applications of imazethapyr (125 fb 125 g ai ha-1). No visual phytotoxicity was observed on the succeeding crops of wheat, mustard, chickpea, lentil, and corn from any of the herbicide treatments applied in IMI-rice.

An experiment was conducted in 2022 and 2023 at multiple locations in North Carolina to identify alternative herbicide combinations capable of providing effective preplant foliar weed control when glyphosate is unavailable. All combinations containing rimsulfuron + thifensulfuron provided 95% to 98% control of henbit, 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 on purple cudweed, providing control comparable to glyphosate (≥ 97%). Tiafenacil alone provided limited control of most of the weed species evaluated in this study, but showed compatibility in mixtures, suggesting 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.

Nursery crop producers in the Southeastern U.S. use open ponds of captured water for irrigating container-grown plants, often without filtration. Many growers perceive irrigation water as a source of weed seed dispersal, but data on the presence of weed seeds in nursery irrigation ponds are lacking. The presence and diversity of viable weed seeds in irrigation pond water samples from six commercial container nurseries in central and eastern North Carolina, U.S.A., were documented in the spring, summer, and late summer for two consecutive years. Irrigation pond water was filtered in 75,708-L increments using a custom-fabricated filtration system. The sample volume was chosen to approximate daily irrigation for 0.405 ha. A total of 216 filtrate samples were collected, six for each location, season, and year. Filtrates were spread on soilless substrate in plastic trays, and seedling emergence was recorded every seven days for twelve weeks. Irrigation samples from all locations, seasons, and years contained viable seeds. A total of 75 different taxa were present in the irrigation filtrates, including 28 weed species common to container nurseries. The average number of seeds collected at each location ranged from 9 to 35 per 75,708-L sample. Averaged across years and locations, there were 12.5, 24.8, and 18.2 germinable seeds 75,708 L-1 in spring, summer, and late summer collections, respectively. Some common weed species, such as eclipta, marsh yellowcress, large crabgrass, flexuous bittercress, and spotted spurge, were present in samples from each season’s collections, while other species were unique to a single season. Although irrigation water introduced weed seeds, the number of weed seeds was small compared to other potential sources of weed seed dispersal within the nursery environment.

Research was conducted to evaluate the influence of adjuvants on hexazinone efficacy for smut grass control in greenhouse and field conditions. The greenhouse experiment was established in 2023 with two runs, comprising hexazinone at 1.12 kg ai ha-1, applied alone or with adjuvants (Grounded, NanoPro, and Sorbyx), and six simulated rainfall accumulation volumes (0, 6, 12, 25, 50, and 100 mm). In field trials, hexazinone was applied at 1.12 kg ai ha-1 with different adjuvants (BREAK-THRU, Grounded, NanoPro, and Sorbyx), and a non-treated control to small smut grass at Marianna, FL, in 2022 and 2023, and giant smut grass at Ona, FL, in 2022 and 2023. In the greenhouse experiment, the addition of all adjuvants to hexazinone improved efficacy, resulting in >78% control (30 DAT), <50% biomass (% of the non-treated control 30 DAT), and little to no regrowth by 60 DAT; applying hexazinone without an adjuvant resulted in <70% control (30 DAT), >52% biomass, and regrowth by 60 DAT. Similarly, adding Grounded, NanoPro, and Sorbyx to hexazinone in the field resulted in >63% smut grass density reduction. However, adding BREAK-THRU to hexazinone did not enhance its efficacy. Adjuvants Grounded, NanoPro, and Sorbyx enhanced the effectiveness of hexazinone in both the greenhouse and the field, indicating their potential for effective smut grass management.

The widespread use of atrazine in corn since the 1960s has raised environmental concerns, such as ground and surface water contamination. The U.S. Environmental Protection Agency has proposed label restrictions on atrazine to address these concerns and requires applicators to achieve herbicide mitigation points before applying herbicides. One way to achieve mitigation points is to reduce the proportion of the field that is treated. Therefore, research was conducted in 2023 in Arkansas, Mississippi, Tennessee, North Carolina, Indiana, and Virginia, and in 2024 in Arkansas, Tennessee, and Indiana, to determine whether targeted applications can mitigate atrazine use in corn while maintaining weed control levels comparable to those achieved with broadcast applications. All plots, except the nontreated control, received paraquat and S-metolachlor immediately after planting in 2023, with amicarbazone and metribuzin added in 2024. Combinations of atrazine, glyphosate, and mesotrione were applied postemergence either broadcast, target-applied to emerged weeds, or a combination of broadcast and target-applied. Targeted applications of herbicides did not differ in weed control, including Palmer amaranth and morningglory species, compared to broadcast applications of the same active ingredients. No injury or differences in corn grain yield were observed. Targeted applications in 2023 covered 86% of the area, on average, while 52% of the area was sprayed on average in 2024. Differences in the area sprayed during the targeted application between years can be attributed to the reduced area of weed emergence from a more robust residual herbicide combination in 2024. Based on this research, targeted spray technology can reduce atrazine use in corn while providing weed control comparable to that achieved with broadcast applications.

The increasing prevalence of herbicide-resistant weeds underscores the need to integrate non- chemical weed management approaches in soybean. Weed electrocution may be a viable option; however, limited research exists on the subject. A multi-state study was conducted to evaluate electrocution as a late-season weed control method in soybean across six Midwestern states, including Illinois, Indiana, Iowa, Kansas, Missouri, and Nebraska. The Weed Zapper™ electrocution implement was assessed across thirteen site-years during 2021 and 2022. The objectives of this study were to (i) evaluate the efficacy of weed electrocution on various weed species at travel speeds of 4.8 and 8.1 km h⁻¹, and (ii) compare the efficacy with other commercially available weed control options. Other non-chemical weed control treatments, which varied by location and were evaluated at selected site-years, included an inter-row cultivator, a tine cultivator, a row shaver, and a weed wiper. Weed species differed in their responses to electrocution, with the greatest control observed for giant ragweed (85%) at 14 d after treatment (DAT). Waterhemp control ranged from 43% to 78% across seven site-years, with ≥70% control achieved at four site-years. Averaged across weed species, control did not differ between electrocution speeds at 7 DAT, 14 DAT, or at soybean harvest. Weed electrocution generally provided similar or lesser control than other non-chemical treatments. In Illinois, waterhemp control with electrocution (78%) was comparable to single (65%) and sequential pass (88%) inter-row cultivation at 14 DAT in 2022. In Kansas, electrocution provided similar Palmer amaranth control (40%) to the row shaver in 2022, but lesser control in 2021 (50% vs. 73%). The results from this study suggest that weed electrocution could be a component of integrated weed management for late-season weed escapes in soybean.

Herbicide-resistant Palmer amaranth has been problematic within the United States for the past 30 years. The recent introduction of Palmer amaranth into the Pacific Northwest (PNW) prompted extensive surveys in 2023 and 2024 to collect seed samples for herbicide-resistance screening and leaf tissue for resistance-mechanism genotyping. Greenhouse dose-response bioassays were conducted in Kimberly, ID, during the summer of 2024 to assess the response of Palmer amaranth populations to selected postemergence herbicides. Resistance to glyphosate predominated across populations, and reduced sensitivity to 2,4-D, dicamba, and mesotrione was also observed. In contrast, glufosinate and saflufenacil provided effective control of PNW Palmer amaranth populations. Based on the dose-response bioassays, the effective dose required to provide 90% control (ED90) of the suspected glyphosate-resistant populations was 20 to 63-fold compared to the susceptible population. Subsequent 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene duplication analysis was conducted to confirm glyphosate resistance in the Palmer amaranth populations. About 74% (17 of 23) of the Palmer amaranth tissue samples showed gene duplication, with up to 150 copies of the EPSPS gene. The EPSPS gene amplification analysis of plants that survived 2X rate of glyphosate (2,520 g ae ha-1) showed up to 150 EPSPS genes in glyphosate-resistant populations. The widespread glyphosate resistance in the collected samples suggests that Palmer amaranth populations are being introduced into the PNW from locations where resistance to herbicide sites of action has previously evolved.

Cover crops have been progressively adopted by growers as a sustainable approach to control problematic and herbicide-resistant weeds. Understanding the critical period of crop-weed competition is essential for timely and effective weed management tactics in cropping systems. The two-year field experiment was conducted in Alabama to evaluate the effect of a cover crop mixture that included cereal rye, crimson clover, and hairy vetch, and solo cereal rye on the critical period for weed control (CPWC) in soybean. The experiment was implemented in a split-plot design in which the main plots were cover crop mixture, cereal rye, and winter fallow, and subplots were five durations of weed-free and weed-interference plots. The presence of a cover crop mixture and cereal rye delayed the critical timing for weed removal (CTWR) by approximately 2 wk compared with winter fallow. The results in 2019 showed the predicted duration of CPWC following cover crop mixture, cereal rye, and winter fallow was 4.8 wk, 0 wk, and 5.1 wk, respectively. Furthermore, in 2020, the estimated CPWC duration following cover crop mixture, cereal rye, and winter fallow was 1.4 wk, 0.1 wk, and 2.6 wk, respectively. In both years, single-species cereal rye resulted in the shortest CPWC due to its early-season weed suppression, while winter fallow resulted in the longest CPWC duration. In conclusion, a shorter duration of CPWC with the incorporation of cover crops could help soybean growers enhance their weed control and provide greater yield protection to soybeans.

The impact of white-tailed deer browsing on crop yields, specifically soybean yield, has been a problem within agriculture for several decades. In an effort to reduce the losses incurred by deer browsing, several wildlife repellents have been commercialized and marketed for use on soybean. Despite their availability, limited research has been conducted on the ability of these repellents to deter feeding or the effects of these products on weed control when applied in combination with common herbicides. In 2023 and 2024, a field experiment was conducted in four soybean fields to evaluate five commercial deer repellent products (Bobbex, Hinder, Liquid Fence, Plantskydd+, and Penergetic bWV) for their ability to reduce deer browsing on soybean. Each product was applied either once, twice, or three times in conjunction with the preplant burndown, early postemergence, and late postemergence pesticide applications, respectively. Regular assessments of deer browsing were conducted at weekly intervals following applications. Across all locations in 2023 and 2024, all applications of repellent products, even three sequential applications of these products, failed to provide any consistent suppression in deer browsing throughout the growing season. An additional field experiment was conducted during both seasons to evaluate the potential impacts of combinations of common herbicides and deer repellents on weed control and soybean injury. Results from these trials indicate that very few differences in foxtail species, waterhemp, and common cocklebur control and crop injury were observed with any repellent and herbicide combination compared to treatments of post-emergent herbicides alone. Overall, the results from these experiments indicate that combinations of these deer repellent products with herbicides in tank mixtures do not increase or decrease weed control when compared to stand-alone herbicide treatments. There is also no evidence that these repellent products effectively deter deer browsing during the time frame when the soybean plant may be most vulnerable.