Commercial targeted sprayer systems allow producers to reduce herbicide inputs but risks the possibility of not treating emerging weeds. Currently, targeted applications with the John Deere system have five spray sensitivity settings, and no published literature discusses the effects of these settings on detecting and spraying weeds of varying species, sizes, and positions in crops. Research was conducted in Arkansas, Illinois, Indiana, Mississippi, and North Carolina on plantings of corn, cotton, and soybean to determine how various factors might influence the ability of targeted applications to treat weeds. These data included 21 weed species aggregated to six classes with height, width, and densities ranging from 25 to 0.25 cm, 25 to 0.25 cm, and 14.3 to 0.04 plants m−2, respectively. Crop and weed density did not influence the likelihood of treating the weeds. As expected, the sensitivity setting alters the ability to treat weeds. Targeted applications (across sensitivity settings, median weed height and width, and density of 2.4 plants m−2) resulted in a treatment success of 99.6% to 84.4% for Convolvulaceae, 99.1% to 68.8% for decumbent broadleaf weeds, 98.9% to 62.9% for Malvaceae, 99.1% to 70.3% for Poaceae, 98.0% to 48.3% for Amaranthaceae, and 98.5% to 55.8% for yellow nutsedge. Reducing the sensitivity setting reduced the ability to treat weeds. The size of weeds aided targeted application success, with larger weeds being more readily treated through easier detection. Based on these findings, various conditions can affect the outcome of targeted multinozzle applications. Additionally, the analyses highlight some of the parameters to consider when using these technologies.

As mid-southern U.S. rice producers continue to adopt furrow-irrigated rice production practices, supplementary management efforts will be vital in combating Palmer amaranth due to the extended germination period provided by the lack of a continual flood. Previous research has revealed the ability of cover crops to suppress Palmer amaranth emergence in corn, cotton, and soybean production systems; however, research on cover crop weed control efficacy in rice production is scarce. Therefore, trials were initiated in Arkansas in 2022 and 2023 to evaluate the effect of cover crops across five site-years on rice emergence, groundcover, grain yield, and total Palmer amaranth emergence. The cover crops evaluated were cereal rye, winter wheat, Austrian winterpea, and hairy vetch. Cover crop biomass accumulation varied by site-year, ranging from 430 to 3,440 kg ha−1, with cereal rye generally being the most consistent producer of high-quantity biomass across site-years. Rice growth and development were generally unaffected by cover crop establishment; however, all cover crops reduced rice emergence by up to 30% in one site-year. Rice groundcover was reduced by 13% from cereal rye in one site-year 2 wk before heading but cover crops did not affect rough rice grain yield in any of the site-years. Palmer amaranth emergence was reduced by 19% and 35% with cereal rye relative to the absence of a cover crop when rice was planted in April in Marianna, and May in Fayetteville, respectively. In most trials, Palmer amaranth emergence was not reduced by a cereal cover crop. In most instances, legume cover crops resulted in less Palmer amaranth emergence than without a cover crop. Based on these results, legume cover crops appear to provide some suppression of Palmer amaranth emergence in furrow-irrigated rice while having a minimal effect on rice establishment and yield.

Tetflupyrolimet is the first herbicide with a novel site of action (SOA) labeled PRE and early POST for use in agronomic crops to be labeled in the last three decades. Direct-seeded paddy rice field experiments were conducted near Stuttgart, AR, on a silt loam soil and near Keiser, AR, on a clay soil to evaluate tetflupyrolimet-containing herbicide programs in comparison to commercial standards in conventional, imidazolinone-resistant, and quizalofop-resistant rice systems. Additionally, a furrow-irrigated rice experiment was conducted near Colt, AR, and Keiser to ensure weed control with clomazone and tetflupyrolimet mixtures compared to commercial standards. Twelve commonly planted rice cultivars were also evaluated in response to a single PRE or POST (2- to 3-leaf rice) application of tetflupyrolimet at 200 or 400 g ai ha−1 in a paddy rice system near Colt. When averaged over soil texture and site-year, all herbicide programs provided ≥98% barnyardgrass control at 56 d after (DA) the last application. Visible rice injury varied for each rice system. Still, injury rarely differed among herbicide programs, except at a single evaluation timing in the conventional (7 DA, 3- to 4-leaf applications) and quizalofop-resistant (preflood) systems. All 12 rice cultivars displayed high tolerance to a single PRE or POST application of tetflupyrolimet at 200 or 400 g ai ha−1. No visible injury, stand loss, or negative impact on rice maturity or reduced grain yield was observed for any cultivar. Tetflupyrolimet will be an effective alternative SOA in a program approach for barnyardgrass while maintaining excellent rice crop safety.

Tetflupyrolimet is the first herbicide with a novel site of action to be commercialized for use in agronomic crops in three decades. Direct-seed rice field experiments were conducted at research facilities near Stuttgart (silt loam), AR, and Keiser (clay), AR, to evaluate tetflupyrolimet as a preemergence herbicide versus commercial standards. Greenhouse experiments determined the influence of soil moisture on pre- and postemergence barnyardgrass control with tetflupyrolimet and clomazone and the impact of a delayed flood on efficacy when POST-applied. For the field experiments, clomazone, tetflupyrolimet, and quinclorac were applied individually PRE at 336 and 560, 134 and 224, and 336 and 560 g ai ha−1, respectively, on a silt loam and clay soil, along with clomazone + tetflupyrolimet and clomazone + quinclorac at the same rates. The soil moisture experiment included a single PRE and a single POST application of clomazone at 336 g ai ha−1, of tetflupyrolimet at 134 g ai ha−1, and of a mixture at the respective rates on a silt loam soil at 50%, 75%, and 100% of field capacity. For the flood timing experiment, tetflupyrolimet was applied to 2- to 3-leaf barnyardgrass at 134 g ai ha−1, and a flood was established at 4 h after treatment (HAT) and 5 and 10 d after treatment (DAT). Barnyardgrass control with a tetflupyrolimet and clomazone mixture was comparable to clomazone + quinclorac when averaged over all evaluations on silt loam and clay texture soils (≥91%). Soil moisture interacted with herbicide treatments for PRE and POST barnyardgrass efficacy when averaged over DAT, with tetflupyrolimet + clomazone generally providing the greatest and most consistent control across regimes. Flooding barnyardgrass at 4 HAT provided superior control to later flood timings. Tetflupyrolimet is an effective residual barnyardgrass herbicide, and the addition of clomazone will aid in providing consistent control across varying soil moisture conditions.

Furrow-irrigated rice (Oryza sativa L.) hectares are increasing in the Midsouth. The lack of sustained flooding creates a favorable environment for weed emergence and persistence, which makes Palmer amaranth (Amaranthus palmeri S. Watson) difficult to control throughout the growing season. The negative yield impacts associated with season-long A. palmeri interference in corn (Zea mays L.), cotton (Gossypium hirsutum L.), and soybean [Glycine max (L.) Merr.] have been evaluated. However, there is limited knowledge of the weed’s ability to influence rice grain yield. Research was initiated in 2022 and 2023 to determine the effect of A. palmeri time of emergence relative to rice on weed seed production and grain yield. Cotyledon-stage A. palmeri plants were marked every 7 d, beginning 1 wk before rice emergence through 4 wk after rice emergence. Amaranthus palmeri seed production decreased exponentially as emergence timing was delayed relative to rice, and seed production increased by 447 seed plant−1 for every 1-g increase in weed biomass. Without rice competition and from the earliest emergence timing, A. palmeri produced 540,000 seeds plant−1. Amaranthus palmeri that emerged 1 wk before the crop had the greatest spatial influence on rice, with grain yield loss of 5% and 50% at a distance of 1.4 m and 0.40 m from the weed, respectively. As A. palmeri emergence was delayed, the area of influence decreased. However, A. palmeri plants emerging 3.5 wk after rice emergence still negatively affected grain yield and produced sufficient seed to replenish the soil seedbank, potentially impacting long-term crop management decisions. These results show that the time of A. palmeri emergence is a crucial factor influencing rice grain yield and weed seed production, which can be used to determine the consequences of escapes in rice.

As herbicide resistance continues to render commonly used rice herbicides ineffective, alternative sites of action are paramount to maintaining yield and producer profitability. Combining a slow-release formulation and a fenclorim seed treatment might allow the safe use of S-metolachlor in rice. Experiments were initiated in 2022 and 2023 near Colt, AR, on a silt loam soil to evaluate crop safety using a capsule suspension (CS) formulation of S-metolachlor and a fenclorim seed treatment in rice. The first experiment assessed the tolerance of two cultivars (‘Diamond’ and ‘DG263L’) to three rates (0.42, 0.84, and 1.68 kg ai ha−1) of a CS S-metolachlor at a delayed preemergence (DPRE) application timing in conjunction with a fenclorim seed treatment. The second experiment evaluated a 1- to 2-leaf (EPOST) application of a CS S-metolachlor at 0.56 and 1.12 kg ai ha−1 to fenclorim-treated rice. Fenclorim reduced injury and partially protected rice yield when S-metolachlor was applied DPRE at 1.68 kg ai ha−1 in both years. However, in one year, under adverse conditions, rice yields were only 65% and 66% of the nontreated control for fenclorim-treated ‘Diamond’ and ‘DG263L’, respectively. An EPOST application of S-metolachlor at 1.12 kg ai ha−1 resulted in 44% to 51% visible injury 35 d after treatment. Relative rice yields were 88% and 89% of the nontreated weed-free treatment in 2022 and 2023, respectively. Fenclorim provided enhanced crop safety at both the 0.84 and 1.68 kg ai ha−1 rates of S-metolachlor. However, the potential for reduced yield can arise when unfavorable conditions occur soon after application. An EPOST application timing of CS S-metolachlor at 0.56 kg ai ha−1 may be a viable option in rice, but 1.12 kg ai ha−1 is too high on a silt loam soil, resulting in significant rice injury.

New machine-vision technologies like the John Deere See & Spray™ could provide the opportunity to reduce herbicide use by detecting weeds and target-spraying herbicides simultaneously. Experiments were conducted for 2 yr in Keiser, AR, and Greenville, MS, to compare residual herbicide timings and targeted spray applications versus traditional broadcast herbicide programs in glyphosate/glufosinate/dicamba-resistant soybean. Treatments utilized consistent herbicides and rates with a preemergence (PRE) application followed by an early postemergence (EPOST) dicamba application followed by a mid-postemergence (MPOST) glufosinate application. All treatments included a residual at PRE and excluded or included a residual EPOST and MPOST. Additionally, the herbicide application method was considered, with traditional broadcast applications, broadcasted residual + targeted applications of postemergence herbicides (dual tank), or targeted applications of all herbicides (single tank). Targeted applications provided comparable control to broadcast applications with a ≤1% decrease in efficacy and overall control ≥93% for Palmer amaranth, broadleaf signalgrass, morningglory species, and purslane species. Additionally, targeted sprays slightly reduced soybean injury by at most 5 percentage points across all evaluations, and these effects did not translate to a yield increase at harvest. The relationship between weed area and targeted sprayed area also indicates that nozzle angle can influence potential herbicide savings, with narrower nozzle angles spraying less area. On average, targeted sprays saved a range of 28.4% to 62.4% on postemergence herbicides. On the basis of these results, with specific machine settings, targeted application programs could reduce the amount of herbicide applied while providing weed control comparable to that of traditional broadcast applications.

Tiafenacil is a new nonselective protoporphyrinogen IX oxidase (PPO)–inhibiting herbicide with both grass and broadleaf activity labeled for preplant application to corn, cotton, soybean, and wheat. Early-season corn emergence and growth often coincides in the mid-South with preplant herbicide application in cotton and soybean, thereby increasing opportunity for off-target herbicide movement from adjacent fields. Field studies were conducted in 2022 to identify the impacts of reduced rates of tiafenacil (12.5% to 0.4% of the lowest labeled application rate of 24.64 g ai ha–1) applied to two- or four-leaf corn. Corn injury 1 wk after treatment (WAT) for the two- and four-leaf growth stages ranged from 31% to 6% and 37% to 9%, respectively, whereas at 2 WAT these respective ranges were 21.7% to 4% and 22.5% to 7.2%. By 4 WAT, visible injury following the two- and four-leaf exposure timing was no greater than 8% in all instances except the highest tiafenacil rate applied at the four-leaf growth stage (13%). Tiafenacil had no negative season-long impact, as the early-season injury observed was not manifested in a reduction in corn height 2 WAT or yield. Application of tiafenacil directly adjacent to corn in early vegetative stages of growth should be avoided. In cases where off-target movement does occur, however, affected corn should be expected to fully recover with no impact on growth and yield, assuming adequate growing conditions and agronomic/pest management practices are provided.

Italian ryegrass control is one of the most significant limitations in wheat production in the United States today. Resistance to Herbicide Resistance Action Committee (HRAC)/Weed Science Society of America (WSSA) Groups 1, 2, and 9 in Arkansas have further complicated postemergence control, whereas residual herbicides still show effective weed control. One problem is the potential of HRAC/WSSA Group 15 herbicides to injure wheat when applied preemergence, indicating the need for a herbicide safener. A series of experiments were conducted in Fayetteville, AR, to evaluate crop tolerance and Italian ryegrass control using a capsule suspension (CS) formulation of S-metolachlor in conjunction with fenclorim-treated wheat. Experiments were conducted as a two-factor factorial with S-metolachlor applied at three rates (0.37, 0.74, and 1.12 kg ai ha–1) and a microencapsulated formulation of acetochlor at 1.05 kg ai ha–1, and three rates of a fenclorim seed treatment at 0, 0.5, and 2.0 g ai kg–1 of seed. Separate experiments utilized either a preemergence (PRE) or a delayed-preemergence (DPRE) application timing. In both experiments, S-metolachlor at 0.74 and 1.12 kg ai ha–1 provided 77% to 96% control of Italian ryegrass by preharvest, whereas acetochlor only provided 49% to 72% control. Visible wheat injury from PRE applications ranged from 7% to 49% for all treatments 21 d after treatment (DAT), with a reduction in injury when fenclorim-treated wheat was used for both the 0.74 and 1.12 kg ai ha–1 rate of S-metolachlor. In the DPRE experiments, wheat injury ranged from 5% to 16% 21 DAT with no noticeable safening from the presence of fenclorim at any herbicide rate. The results of these experiments indicate that a DPRE application using a CS formulation of S-metolachlor would be more favorable for producers to mitigate the potential for injury to wheat while providing Italian ryegrass control. Additionally, at the DPRE application timing, fenclorim is unnecessary for S-metolachlor to be safely applied at the rates evaluated.

Herbicide-resistant Palmer amaranth is creating additional challenges for producers who choose to adopt a furrow-irrigated rice production system due to the absence of a sustained flood, enabling extended weed emergence. Fluridone has been shown to effectively control Palmer amaranth in cotton production systems and was recently registered for use in rice. Experiments were initiated in 2022 and 2023 1) to evaluate Palmer amaranth control and rice tolerance to preemergence- and postemergence-applied fluridone at 0.5× (84 g ai ha−1) and 1× (168 g ai ha−1) rates on a silt loam soil; and 2) assess the effect of various herbicide programs that contain fluridone on Palmer amaranth biomass, seed production, and rough rice grain yield. Preemergence applications of fluridone at a 1× rate in combination with clomazone resulted in 84% control of Palmer amaranth 21 d after treatment (DAT). Fluridone, in combination with clomazone preemergence, caused up to 36% rice injury 21 DAT; however, early season injury did not negatively affect rice yields. Palmer amaranth biomass and fecundity were reduced with herbicide programs that included fluridone plus florpyrauxifen-benzyl, and, in some instances, there was no Palmer amaranth biomass or seed production following multiple applications of both herbicides. Fluridone- and florpyrauxifen-benzyl–based herbicide programs achieved effective control of Palmer amaranth when applied timely, but injury to hybrid rice is enhanced with preemergence applications of fluridone that are not permitted with the current label.

Commercialization of florpyrauxifen-benzyl as Loyant® in 2018 as a synthetic auxin herbicide in rice was followed by soybean injury due to off-target movement of spray applications in the mid-southern United States. Concerns surrounding off-target movement led to the exploration of an alternative application method to help alleviate the issue. Field experiments were conducted in 2020 and 2021 to explore the likelihood of a reduction in soybean injury following applications of florpyrauxifen-benzyl coated on urea in narrow- and wide-row soybean systems and to determine the likelihood of volatilization from this novel application method. Florpyrauxifen-benzyl spray-applied at 0.18 g ai ha−1 caused greater than 60% injury, whereas coating the herbicide on urea at 5.63 g ai ha−1 never exceeded 30% injury in narrow-row soybean. Similarly, florpyrauxifen-benzyl spray-applied at 0.18 g ai ha−1 caused greater than 50% injury, whereas coating the herbicide on urea at 5.63 g ai ha−1 never exceeded 30% injury in wide-row soybean. As soybean injury increased, relative yield decreased in both narrow- and wide-row soybean. Spray-applied florpyrauxifen-benzyl decreased relative soybean groundcover, yield components, and soybean survival rate as the herbicide rate increased, whereas coating the herbicide on urea resulted in little to no decrease in both narrow- and wide-row soybean assessments. No negative impacts on relative yield and yield components of soybean from florpyrauxifen-benzyl coated on urea indicates that even though visible injury may persist, there is a low likelihood of any yield losses associated with the herbicide exposure using this application method. Additionally, coating the florpyrauxifen-benzyl on urea did not increase the likelihood of volatilization under any of the evaluated soil moisture conditions. Overall, applying florpyrauxifen-benzyl coated on urea is likely to be a safer application method and can reduce soybean injury compared to spray-applying the herbicide when favorable off-target movement conditions exist.