Abstract 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.

Abstract 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.

Abstract 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.

Abstract 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.

Abstract 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.

Abstract 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 (ED 90 ) 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.

Abstract 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.

Abstract Cotton production in the Texas High Plains faces significant challenges due to water scarcity resulting from uneven rainfall patterns and declining levels of the Ogallala aquifer. Deficit or reduced irrigation is one of the most common water management strategies to increase water use efficiency and cotton productivity in the region. However, deficit irrigation can affect the efficacy of herbicides on weeds. This study investigates how varying irrigation levels affect herbicide efficacy on weeds in cotton production systems. A two-year field study was conducted at Texas Tech University Quaker Research Farm in 2023 and 2024. The experiment was randomized three times in a split-plot design with two irrigation levels: I1 [100% crop evapotranspiration (ET c ) replacement] and I2 [50% ET c replacement] as the main plot factor and different pre-emergent (PRE) and post-emergent (POST) herbicide combinations as the subplot factor. Results indicated that reducing the irrigation level to I2 did not affect the total weed density or biomass production but resulted in decreased Palmer amaranth height and biomass production compared to I1. Among herbicide treatments, acetochlor, prometryn, or S -metolachlor PRE fb glyphosate + acetochlor, prometryn, or S -metolachlor POST provided the most effective weed control, reducing total weed density, Palmer amaranth weed density and biomass compared to the untreated control and to PRE alone. Although I2 resulted in lower plant height in both years than I1, it produced comparable cotton biomass and lint yield. Among the herbicide treatments, PRE fb glyphosate + residual herbicide POST yielded significantly higher lint yield than the untreated control in both years. In conclusion, the study demonstrates that deficit irrigation is an effective water conservation technique that maintains cotton yield and herbicide efficacy. Additionally, using PRE fb POST herbicide combinations, farmers can achieve effective weed control and sustain cotton productivity in semi-arid regions.

Abstract In the U.S. Upper Midwest, 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 systems under varying soil conditions. At Arlington (silt loam soil), herbicide concentrations at soil sampling, 21 d after the fourth and final application time, which followed a series of treatments from planting to V1, were similar across application times, while at Brooklyn (sandy loam soil), herbicide concentrations were usually higher in later applications. Despite these differences, weed density at POST was similar across application times within each site. However, an additional late POST 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.

Abstract 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.