Managing yellow nutsedge and southern root-knot nematode (SRKN) is particularly challenging in organic sweetpotato production. Anaerobic soil disinfestation (ASD) has emerged as a promising nonchemical pest management strategy that entails incorporating labile carbon amendments into the soil, covering the soil with impermeable plastic mulch, and irrigating the amended soil to saturation. Field studies were conducted at Clemson University in Charleston, South Carolina, in the 2023 and 2024 growing seasons, to evaluate the effect of ASD on yellow nutsedge and SRKN. Treatments were structured as a factorial arrangement of three carbon amendments (Brassica residue [BR], chicken manure + molasses [CM+M], and cotton seed meal [CSM]) and an unamended control (UC) by four sweetpotato clones (Bayou Belle, Monaco, Murasaki-29, and USDA-18-040) with four replications using a randomized complete block design. ASD was terminated 3 wk after initiation, and sweetpotato slips were planted 1 wk after ASD termination. Greater cumulative anaerobicity was observed in the CM+M and CSM treatments with increments exceeding 220% relative to UC at ASD termination. Six weeks after planting, yellow nutsedge densities across all sweetpotato clones were significantly lower with CM+M (4 to 10 plants m-2) and CSM (6 to 8 plants m-2) treatments than the UC (21 to 27 plants m-2). Both bunch cultivars (Monaco and USDA-18-040) and spreading cultivars (Bayou Belle and Murasaki-29) sweetpotato clones resulted in similar yellow nutsedge densities. Soil population densities of SRKN at 16 wk after planting were reduced by 23% to 44% in CM+M treatments and by 29% to 46% in CSM treatments, relative to the UC. Marketable sweetpotato yield rose from 47% to 131% with the CMM and CSM treatments compared with UC yield. The findings of this study demonstrate that CM+M and CSM-induced ASD have the potential to suppress yellow nutsedge and SRKN in organic sweetpotato production systems while increasing the marketable sweetpotato yield.
Timely soybean planting is important for maximizing yield, with farmers tending to plant their crops earlier. However, when a soybean crop is planted ultra-early (before April 15th in Ohio), seedlings are exposed to cold and moist conditions that can lead to a smaller plant population, delayed canopy closure, and reduced ability to compete with weeds. The objective of this study was to evaluate herbicide treatments for their effect on weed development and soybean yield when the crop was planted ultra-early (before April 15) and at a normal time (early to mid-May in Ohio). Weed biomass was significantly reduced when the crop was treated at early postemergence. However, preemergence followed by early postemergence herbicide applications were generally less effective at suppressing weeds than treatments that included an early postemergence and late postemergence application, for which weed density was reduced and weed control was improved later in the season. In 2024, when the number of soybean plants was very low due to freeze damage, an early postemergence application of dicamba + glyphosate and a late postemergence application of glyphosate + glufosinate + S-metolachlor resulted in the greatest weed control and yield from the crop that was planted ultra-early. The results from this study indicate that when soybean was planted ultra-early, treatments that included two postemergence applications, particularly those that included a residual herbicide applied at late postemergence, were better suited to maintain weed suppression later in the season and protect soybean yield potential when the soybean plant population was very low and pressure from grass weeds was high.
This research was conducted in response to a report by a producer in southwestern Ontario of severe corn injury following an application that included multiple herbicides, an activator adjuvant, and a drift reduction agent. Eight field trials were conducted between 2024 and 2025 near Ridgetown, Ontario, Canada, to evaluate corn tolerance to mixtures of multiple active ingredients, an adjuvant, and drift retardent applied at two early postemergence growth stages (V2 to V3 and V3 to V4). Isoxaflutole applied alone or in combination with atrazine at either growth stage caused minimal visible corn injury at all time points, with <= 1% injury at 1 wk after application (WAA) and no injury at 2, 4, 6, and 8 WAA. Isoxaflutole + atrazine + glyphosate, applied at the V2-V3 or V3-V4 stage, caused 7% and 9% visible corn injury at 1 WAA and 3% and 5% at 2 WAA, respectively; however, visible corn injury was <= 1% at 4, 6, and 8 WAA. Isoxaflutole + atrazine + glyphosate + HiActivate, applied at the V2-V3 and V3-V4 stages, caused greater and more persistent visible corn injury, with 7% and 16% injury at 1 WAA and 5% and 10% injury at 2 WAA, respectively; visible corn injury declined to <= 5% at 4, 6, and 8 WAA. Isoxaflutole + atrazine + glyphosate + HiActivate + InterLock, applied at the V2-V3 and V3-V4 stages, caused 17% and 28% visible corn injury at 1 WAA and 11% and 17% at 2 WAA, respectively. Visible corn injury persisted with up to 8%, 7%, and 4% injury at 4, 6, and 8 WAA, respectively. There was no adverse effect on corn height, biomass, and grain yield with any of the treatments evaluated at either application timing. Results indicate that tank mixtures with multiple active ingredients can increase visible corn injury, but the injury was transient and did not affect yield.
Integrated weed management combines cultural practices with herbicides to achieve sustainable weed control while reducing dependence on chemical inputs. However, limited information is available on how these practices interact to optimize weed suppression and minimize yield loss in peanut. Field studies were conducted in 2023 and 2024 to evaluate the effect of tillage systems (conventional or strip-tillage), planting dates (late April, mid-May, or early June), and three herbicide programs on weed management in peanut. Densities of red spiderling and Benghal dayflower were reduced by more than 50% with conventional tillage compared with strip-tillage 28 d after preemergence herbicides were applied. In contrast, sicklepod was not affected by tillage system. Without preemergence herbicides, crowfoot grass and goosegrass densities were more than 60% greater where strip-tillage was practiced, although herbicides minimized these differences. Broadleaf weed biomass was also reduced with conventional tillage but it had no effect on grass biomass following a herbicide application at mid-postemergence. Peanut planted in late April or mid-May had lower Benghal dayflower and grass densities than early June plantings, while planting date did not influence red spiderling or sicklepod density. Flumioxazin applied alone provided >= 80% weed control, and adding diclosulam improved control of Benghal dayflower, but not red spiderling, crowfoot grass, goosegrass, or sicklepod. Yields were similar between tillage systems when a full array of herbicides were applied; however, conventional tillage with reduced herbicide input yielded 23% more than strip-tillage. Overall, conventional tillage allows greater herbicide reduction than strip-tillage, and planting in late April or early May optimizes weed suppression and peanut yield compared with planting in early June.
No effective preemergence or postemergence herbicides are currently available to use on sugar beets for managing kochia and Palmer amaranth that are resistant to glyphosate and acetolactate synthase. To evaluate a new herbicide option, field experiments were conducted to assess the efficacy of a preemergence application of metamitron to sugar beet crops. Studies were carried out in Lingle, Wyoming, and Scottsbluff, Nebraska, in 2019. Studies were repeated in 2020 at the Scottsbluff location, and two locations in Oregon, Nyssa and Ontario. Cycloate (4.03 kg ai ha-1), ethofumesate (1.58 kg ai ha-1), metamitron (2.82, 5.63, and 7 kg ai ha-1), and metamitron + ethofumesate (5.63 + 1.58 kg ai ha-1) were applied preemergence. Metamitron (5.63 kg ai ha-1) + ethofumesate (1.58 kg ai ha-1) was applied preemergence followed by (fb) ethofumesate (1.58 kg ai ha-1) or acetochlor (1.26 kg ai ha-1) applied at the 2 to 4 true-leaf (TL) stage of sugar beet, ethofumesate or acetochlor at the 2 to 4 TL and 6 to 8 TL stages, and ethofumesate fb acetochlor at the 2 to 4 TL and 6 to 8 TL stages, respectively. A nontreated control and weed-free check (glyphosate applied at 2 to 4 TL and 6 to 8 TL stages of sugar beet) were included for treatment comparison. Ethofumesate applied alone preemergence provided <= 65% control of Palmer amaranth, common lambsquarters, and redroot pigweed relative to >= 95% control when metamitron (5.63 kg ai ha-1) was applied as a tank mixture partner. Any treatment containing metamitron (>= 5.63 kg ai ha-1) provided >= 80% control of common lambsquarters, redroot pigweed, and Palmer amaranth, but not kochia. When kochia was not present, any herbicide combination that contained metamitron (>= 5.63 kg ai ha-1) provided similar sugar beet root yield and recoverable sugar as glyphosate-based treatments. Based on the findings of this research, metamitron (>= 5.63 kg ai ha-1) applied preemergence will control Palmer amaranth, common lambsquarters, and redroot pigweed until other herbicides, such as those that inhibit very-long-chain fatty acids, can be applied at the 2 TL stage of sugar beet.
Weed seed buoyancy and survival in irrigation ponds were investigated as part of a larger study evaluating the potential for weed seed spread via overhead irrigation in container nurseries. Seed buoyancy was assessed for 13 weed species commonly found in container nurseries. Two of the 13 species were tested with the pappus intact or removed. Seeds were placed in water, and seed settling was recorded every 24 h for 168 h. Among the species tested, seed buoyancy ranged from 0% to 100%. Eclipta and marsh yellowcress maintained 100% and 99% buoyancy. In contrast, flexuous bittercress and yellow woodsorrel had 2% and 0% buoyancy. An attached pappus significantly increased seed buoyancy for both common groundsel and dogfennel. To test seed survival in irrigation ponds, seeds of spotted spurge, eclipta, flexuous bittercress, and yellow woodsorrel were placed in mesh bags and submerged at a depth of 60 cm in irrigation ponds at four nurseries. Seeds were collected from each location at 7, 15, 21, 30, 60, 90, 120, 240, and 360 d after submergence then germinated. All weed species germinated following 240 d of submergence. Flexuous bittercress and eclipta maintained greater than 80% germination following 360 d of submergence in three of four locations. In contrast, yellow woodsorrel seed germination was less than 15% following 240 d of submergence and less than 5% after 360 d in three of four locations. Spotted spurge seed germination declined over time but remained greater than 15% following 360 d of submergence. Results of these experiments show that seeds of several common nursery weeds are buoyant and remain viable while submerged for extended periods of time in irrigation ponds. Seeds that are both buoyant and survive in water may have greater potential for distribution by irrigation systems.
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, but their efficacy can be inconsistent due to delayed or excessive rain, 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 in Alabama, in 2023 and 2024, to evaluate the effect of simulated rain timing on the efficacy of quinclorac and hexazinone in controlling knotroot foxtail. Knotroot foxtail plants averaging 28 cm tall were treated with quinclorac (0.4 kg ae ha-1) or hexazinone (0.8 kg ai ha-1), followed by simulated rain (6.3 mm) applied at 0, 3, 6, 9, 12, and 15 d after herbicide treatment. Hexazinone provided greater knotroot foxtail control and rhizome biomass reduction than quinclorac. At 51 d after each rain treatment (DAERT), hexazinone provided 90% control compared with 76% control with quinclorac. In 2024, at 51 DAERT, control with hexazinone ranged from 99% to 92% when rain occurred within 0 to 6 d after application, but declined to 85% and 81% when rain was delayed until 12 and 15 d, respectively. Similarly, knotroot foxtail was controlled by 87% to 77% when rain occurred within 0 to 9 d after quinclorac treatment, but control dropped to 67% to 62% when simulated rain was delayed until 12 to 15 d after the herbicide was applied. Relative to nontreated control plants, knotroot foxtail rhizome biomass was reduced by 72% and 42% after applications of hexazinone and quinclorac, respectively. An early rain (0 to 6 d) after herbicide application enhanced knotroot foxtail control, whereas delayed rain 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.
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.
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.
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 small fruit and vegetable crop fields in Florida. Trials were conducted to identify the most effective herbicide options from active ingredients registered for use in row middles. Lactofen (404 g ai ha(-1)) applied preemergence 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) resulted in 75% to 93% control of vegetative green kyllinga shoots that were 1 cm tall. Glufosinate applied at rates of 378 and 755 g ai ha (-1) delivered 96% and 100% control, respectively, on vegetative shoots that were 9 cm tall. Glufosinate was less effective on flowering green kyllinga, with >90% control achieved only 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 preemergence applications of lactofen or pendimethalin followed by postemergence applications of glufosinate prior to flowering are effective management options for green kyllinga.
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.
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 (IMI)-resistant 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-resistant rice in northwestern India. Field experiments were conducted in Karnal, India, from the 2020 through 2023 growing seasons to 1) evaluate the timing and rates of imidazolinone herbicides for effective weed control in IMI-resistant rice under DSR conditions, and 2) assess the potential carryover effects of IMI herbicides on succeeding crops. Results showed that sequential early postemergence applications of imazethapyr followed by (fb) late postemergence applications of either 100 fb 150 g ai ha-1 or 125 fb 125 g ai ha-1) effectively reduced the biomass of key weed species by 83% to 100%, including barnyardgrass, crowfootgrass, and Chinese sprangletop, and provided yields that were similar to weed-free treatments. These sequential postemergence treatments were consistently more effective than conventional preemergence herbicide applications of oxadiargyl fb a postemergence application of bispyribac-sodium. Sequential preemergence fb postemergence applications of imazethapyr were relatively less effective in controlling weeds and minimizing yield losses compared to sequential postemergence applications. However, in the second and third years, oxadiargyl (90 g ai ha-1) applied preemergence fb imazethapyr (100 g ai ha-1) applied postemergence achieved comparable weed control efficiency to those of sequential postemergence applications of imazethapyr (125 fb 125 g ai ha-1). No phytotoxicity was observed in the succeeding crops of wheat, mustard, chickpea, lentil, and corn from any of the herbicide treatments applied to IMI-resistant rice.
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 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, Indiana, Mississippi, North Carolina, Tennessee, and Virginia, and in 2024 in Arkansas, Indiana, and Tennessee 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 controls, 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 control of 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.
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 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.
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 (ETc) replacement] and I2 [50% ETc 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.
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.
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.
Targeted herbicide applications have the potential to reduce herbicide inputs but pose an inherent risk of missing weeds resulting in late-season escapes. Furthermore, relying on targeted residual herbicides may increase weed emergence relative to broadcast applications. Research was conducted over a three-year period in Keiser, AR, to compare traditional broadcast applications to targeted postemergence applications in glyphosate-, glufosinate-, and dicamba-resistant soybean. The herbicide program was consistent across treatments with a broadcast-applied preemergence residual, and a postemergence program including glufosinate + glyphosate + S -metolachlor followed by glufosinate + acetochlor, both broadcast- or target applied at the highest and lowest spray sensitivities. The soil seedbank was similar at trial initiation across treatments, and there was no increase over three years for broadcast and targeted applications at the highest sensitivity. Averaged over application timing, the lowest sensitivity increased the weed density from 867 plants ha -1 to 2,870 plants ha -1 in year two, to 11,300 plants ha -1 in year three. This response is likely due to more Palmer amaranth escapes at harvest (averaged over years) with >1,000 plants ha -1 compared to the highest sensitivity and broadcast treatments. Targeted applications did improve profitability by reducing herbicide use and increasing application efficiency, providing averaged savings of USD $43.22 ha -1 to $129.19 ha -1 relative to broadcast postemergence cost of $227.22 ha -1 . Area sprayed was reduced by 20% to 90%, with the average at early-postemergence being 41.3% and 57.9% and at mid-postemergence equaling 48.1% and 49.3% for the lowest and highest sensitivities, respectively. The only difference in the area sprayed between sensitivity settings occurred early postemergence. Based on the results of this experiment, producers could utilize targeted applications postemergence in soybean to increase profitability, but the lowest sensitivity resulted in unacceptable increases to the weed seedbank, which could impact management in future years.
