The knowledge of the critical periods of crop-weed competition is crucial for designing weed management strategies in cropping systems. In the Lower Yangtze Valley, China, field experiments were conducted in 2011 and 2012 to study the effect of interference from mixed natural weed populations on cotton growth and yield and determine the critical period for weed control (CPWC) in direct-seeded cotton. Two treatments were applied: allowing weeds to infest the crop or keeping plots weed-free for increasing periods (0, 1, 2, 4, 6, 8, 10, 12, 14, and 20 weeks) after crop emergence. The results showed that mixed natural weed infestations led to 35 to 55 cm shorter cotton plants with stem diameters 10 to 13 mm smaller throughout the season, fitting well with modified Gompertz and logistic models, respectively. Season-long competition with weeds reduced the number of fruit branches per plant by 65% to 82%, decreasing boll number per plant by 86% to 96% and single boll weight by approximately 24%. Weed-free seed cotton yields ranged from 2,900 to 3,130 kg ha-1, while yield loss increased with the duration of weed infestation, reaching up to 83% to 96% compared with permanent weed-free plots. Modified Gompertz and logistic models were used to analyze the impact of increasing weed control duration and weed interference on relative seed cotton yield (percentage of season-long weed-free cotton), respectively. Based on a 5% yield-loss threshold, the CPWC was found to be from 145 growing degree days (GDD) to 994 GDD, corresponding to 14 days after emergence (DAE) to 85 DAE. These findings emphasize the importance of implementing effective weed control measures from 14 DAE to 85 DAE in the Lower Yangtze Valley, China, to prevent crop losses exceeding a 5% yield-loss threshold.

Site-specific herbicide applications with remotely piloted aerial application systems (RPAASs) offer the potential for reducing herbicide inputs in turfgrass systems. However, information on spray nozzle selection and application volume for this approach is lacking. The objective of this study was to evaluate the effects of nozzle type and spray volume on the efficacy of site-specific herbicide application in turf using an RPAAS, focusing on large crabgrass control with quinclorac. The research was conducted in 2022 at two College Station, TX sites. The treatments were combinations of three nozzle types [XR 80-015 (conventional, extended range), DG 80-015 (drift guard), and AI 80-015 (air induction) flat fan nozzles] and two spray volumes [10 and 15 L ha-1], applied with a single-nozzle RPAAS. A spray volume of 102 L ha-1 applied with a CO2 pressurized 4-nozzle boom backpack sprayer served as a check for comparison. Two additional treatments were also included: a pure formulated herbicide application (without dilution in water) using an RPAAS equipped with an XR 80-005 flat fan nozzle at 4.6 L ha-1 and an untreated control. The backpack sprayer application resulted in the highest spray solution deposits on large crabgrass plants (12 times more on average), compared to the RPAAS applications. Nevertheless, applications using the RPAAS with the DG and AI nozzles at 10 or 15 L ha-1 provided similar levels of weed control as that of the backpack sprayer at 102 L ha-1, indicating that RPAAS can be effectively used for site-specific herbicide applications in turf. This study also suggests that large crabgrass can be controlled using RPAAS with a range of spray nozzle types at low application volumes in turfgrass. Further research is needed to assess the efficacy of RPAAS-based herbicide applications across a range of herbicides, weed species, and environmental conditions.

Branched broomrape management is of increasing concern to California processing tomato growers. Field research was conducted in 2023 and 2024 to evaluate various application timings of chemigated rimsulfuron alone, preplant incorporated (PPI) sulfosulfuron paired with chemigated rimsulfuron, as well as foliar maleic hydrazide alone and paired with PPI sulfosulfuron and chemigated rimsulfuron. In 2023, all treatments with 70 g ai ha-1 rimsulfuron, alone or paired with PPI sulfosulfuron, reduced broomrape emergence 77 to 92% compared to the nontreated control. In 2024, broomrape pressure was higher, and all rimsulfuron treatments reduced broomrape emergence 68 to 86% compared to the control. In both years, five applications of foliar maleic hydrazide reduced broomrape emergence through at least midseason. The 2024 experiment included a combination treatment of PPI sulfosulfuron, chemigated rimsulfuron, and foliar maleic hydrazide, which resulted in fewer than four broomrape clusters per plot. In a 2024 grower-scale demonstration trial, two application regimes totaling 70 g ai ha-1 of chemigated rimsulfuron reduced broomrape emergence 83 to 89% compared to the control. Overall, chemigated rimsulfuron applied at various timings and rates totaling 70 g ai ha-1 reduced broomrape emergence by two-thirds or more compared to the nontreated plots. No crop injury was observed in trials with rimsulfuron, sulfosulfuron, or maleic hydrazide treatments in small plot trials or with rimsulfuron in the grower-scale demonstration trial. Under a recently approved 24(c) Special Local Need label, California growers can use three applications of rimsulfuron applied via chemigation to suppress broomrape in known infested fields or to reduce the risk of broomrape establishment in fields of concern for this quarantine pest. Promising results from sulfosulfuron and maleic hydrazide suggest that registering additional herbicides could help develop even more robust branched broomrape management programs.

Galium aparine L. var. echinospermum (Wallr.) Cuf., an annual or winter annual broadleaf weed in the Rubiaceae family, has become troublesome due to its herbicide resistance in the wheat fields of the Huang-Huai-Hai region in China. Four cleavers populations (JS-15, SD-10, JS-22, and AH-20) were collected from the wheat fields of Jiangsu, Shandong, and Anhui Province, where florasulam control was absent. This study identified the herbicide resistance patterns and investigated the mechanism underlying the florasulam resistance. The whole-plant dose-response experiments revealed a notable variation in the degree of resistance exhibited by three specific populations towards florasulam, in comparison to the most sensitive populations (S and AH-9), with the highest resistance index reaching 841.4. Acetolactate Synthase gene-sequencing assay found that R plants from JS-15, JS-22, and AH-20 had a Trp-574-Leu mutation, while no known ALS resistance mutations were discovered in SD-10 plants. In vitro ALS enzyme activity assays also indicated that the extractable ALS from the resistant plants of JS-15, JS-22, and AH-20 was greatly resistant to florasulam relative to that of the susceptible. Additionally, according to the resistance rating system, all resistant populations were susceptible to Carfentrazone-ethyl + MCPA-Na and Bipyrazone + Fluroxypyr-methyl. AH-20, JS-15, and JS-22 exhibited resistance to selected ALS, 4-hydroxyphenylpyruvate dioxygenase, and photosystem Ⅱ complex inhibitors, demonstrating RR and RRR resistance profiles, whereas AH-9 displayed S-sensitivity to virtually all tested agents. SD-10, on the other hand, showed RR and RRR resistance to HPPD and PSII inhibitors, but exhibited S-sensitivity specifically to tribenuron-methyl. These findings indicate that a target site-based mechanism drives the resistance to the ALS inhibitor florasulam in cleavers populations, but NTSR resistance may have also contributed (was not investigated). Other herbicides with different sites of action were tested and were active against cleavers.

Weeds incur up to AUD $4 billion in economic loss annually to Australian agriculture. Despite this knowledge, there are few quantitative data on yield loss and control costs caused by weeds to the industry. Reported herein is the economic cost of managing the emerging, invasive Navua sedge weed to the grazing and cropping (sugarcane) industries of northern Queensland, Australia, following its introduction into the region in the 1970’s. Between 2020-2022, through a survey questionnaire given to impacted stakeholders (farmers), information relating to control cost, yield loss, and infestation history were documented. Collated data were analyzed using mainly non-parametric statistics due to the skewed and/or qualitative nature of many of the responses. Invasion history of the weed on farming properties is relatively recent (time: 10-20 yrs), and infestation level, though majorly and currently of low-medium status (median value: 22.5%), varies appreciably amongst properties. Median cost of managing Navua sedge was AU $72.91/hectare (AU $82.06 present value). This cost nor the type of management tactics (chemical vs. integrated weed management [IWM]) did not vary between land use types; however, the labor (relative to chemical and machinery) component of the control cost was the greatest. The currently approved herbicide, halosulfuron-methyl (SempraTM), is largely ineffective in controlling the weed due to its inability to deplete below-ground tubers of the weed. Correlation analyses suggest control costs will continue to increase with increasing Navua sedge infestation over time, especially in grazing lands. Farmers show high awareness of the challenge of managing the new weed incursion. Farmers are using myriads of strategies, including willingness to impose strict biosecurity measures and IWM tactics while waiting for more effective herbicides and promising biocontrol agents to minimize the spread and impact of the weed.

Uncontrolled weeds can cause billions of dollars in yield loss in corn and soybean production fields in the United States. Growers often use herbicides to control weeds to avoid yield loss. The objective of this study was to estimate the cost of herbicides used in corn and soybean production in the United States. On-farm herbicide usage data were extracted from corn (2021) and soybean (2023) surveys of the United States Department of Agriculture–National Agricultural Statistics Service (USDA-NASS 2022a, 2024a) Agricultural Chemical Use Program. Commonly used or known products were assumed for each reported herbicide. Based on the USDA-NASS surveys, approximately 107.8 and 89.1 million kg of herbicides were applied in corn and soybean production in 2021 and 2023, respectively, in the United States. Glyphosate (33.8 million kg; in various salt forms), atrazine (26.8 million kg), and mesotrione (2.4 million kg) were the most widely applied herbicides, on 79%, 65%, and 47% of corn, respectively, planted in 2021 (USDA-NASS 2022b). Similarly, glyphosate (in various salt forms) was the most widely applied herbicide in soybean, followed by 2,4-D (15.9 million kg; in various salt forms) and glufosinate-ammonium (4.4 million kg), which were applied to 58% and 23% of soybean, respectively, planted in 2023 (USDA-NASS 2024c). Using the average retail price of herbicide products from Kansas State University, University of Nebraska−Lincoln, and North Dakota State University publications, herbicides (excluding adjuvants and application costs) would have cost approximately $3.2 and $4.1 billion in corn and soybean in 2021 and 2023, respectively.

Fall-planted cover crops are becoming popular among growers in the Midwest for various reasons, including weed suppression. Cereal rye is the most planted cover crop in Nebraska. Glyphosate availability was limited in 2022, so growers sought information about glyphosate alternatives for terminating cover crops, such as cereal rye. The objectives of this study were to evaluate alternative acetyl coA carboxylase (ACCase)-inhibiting herbicides for terminating cereal rye 15 days before soybean planting (DBSP), at soybean planting day (SPD), and 15 days after soybean planting (DASP) and their effect on weed control, density, biomass, soybean plant stand, and grain yield. Field experiments were conducted from 2018 to 2020 in southcentral Nebraska. Cereal rye biomass collected 15 days after termination was 394, 1,697, and 3,700 kg ha−1 in 2019 and 330, 1,304, and 4,550 kg ha−1 in 2020, respectively, for 15 DBSP at SPD and 15 DASP termination timings. Clethodim provided 77% control of cereal rye 15 DBSP compared with greater than 94% control with fluazifop-P-butyl, fluazifop-P-butyl/fenoxaprop-P-ethyl, quizalofop-P-ethyl, and glyphosate. Similarly, at SPD and 15 DASP termination timings, clethodim resulted in 66% and 31% control of cereal rye, respectively, compared to greater than 92% control with other ACCase-inhibitors and glyphosate. Palmer amaranth control at R5 soybean growth stage was 70%, 88%, and 96%, respectively, at 15 DBSP, SPD, and 15 DASP termination timing. Soybean yield was reduced to 2,184 kg ha−1 when cereal rye was terminated at 15 DASP compared to 4,566 kg ha−1 when terminated at SPD and 4,460 kg ha−1 with 15 DBSP.

Wild oat is a significant weed of cropping systems in the Canadian Prairies. Wild oat resistance to herbicides has increased interest in non-chemical management strategies. Harvest weed seed control techniques such as impact mills or chaff collection have been of interest in Prairie crops, with wild oat identified as a key target. To evaluate impacts of crop rotation maturity, harvest management and harvest weed seed control on wild oat, a study was conducted from 2016-2018 at four locations in the Canadian Prairies. Two-year crop rotations with either early, normal, or late-maturity crops were implemented before barley was seeded across all rotations in the final year. In addition, a second factor of harvest management (swathing or straight cut) was included in the study. Chaff collection was used in this study in an attempt to quantify wild oat seeds that were targetable by harvest weed seed control techniques. The hypothesis was that earlier maturing crops would result in increased wild oat capture at harvest and, therefore, lower wild oat populations. Wild oat density and wild oat biomass were lowest in the early maturing rotations. In addition, wild oat biomass was lower in swathed crops than in straight-cut crops. Wild oat seedbank levels reflected a similar trend with the lowest densities in early maturing rotation, then the normal maturity rotation and the late maturing rotation had the highest seedbank densities. Wild oat densities increased in all crop rotations; however, only harvest weed seed control and crop rotation were implemented as control measures. Wild oat numbers in the chaff were not reflective of the earliness of harvest. Crop yields suggest that competitive winter wheat stands contributed to the success of the early maturing rotations compared to other treatments. Early maturing rotations resulted in reduced wild oat populations, likely through a combination of crop competitiveness and rotational diversity, and harvest weed seed control impact in earlier maturing crops.

Systematically monitoring the baseline sensitivity of troublesome weeds to herbicides is crucial for the early detection of a premature market lifespan of herbicides. Florpyrauxifen-benzyl is one of the most important rice herbicides across the world, which has been used for five years in China. Barnyardgrass is one of the main targeted weed species of florpyrauxifen-benzyl. Totally 114 barnyardgrass populations were collected from rice fields in Jiangsu Province, China, and screened for susceptibility of each population to florpyrauxifen-benzyl by whole-plant bioassays. For all populations, the GR50 doses (the dose causing a 50% reduction in fresh weight of aboveground parts) of florpyrauxifen-benzyl ranged from 1.0 to 34.5 g ai ha-1, with an average of 6.8 g ai ha-1, a baseline sensitivity dose of 3.3 g ai ha-1, and a baseline sensitivity index of 34.5. Twenty-one days after treatment with florpyrauxifen-benzyl at the labeled dose (36 g ai ha-1), 90% of the barnyardgrass populations showed reductions in fresh weight of aboveground parts > 95%. Compared with the baseline sensitivity dose, 63, 44, and seven populations had no resistance (55%), low resistance (39%), and moderate resistance (6%) to florpyrauxifen-benzyl, respectively. Furthermore, the GR50 distribution of barnyardgrass populations did not show a significant correlation with city, planting methods (direct-seeding or transplanting), and rice species (ssp. indica or ssp. japonica) at the seed-collection rice fields (P > 0.05). In conclusion, florpyrauxifen-benzyl remains effective for barnyardgrass control in rice fields despite serious resistance challenges.

Field studies were conducted on certified organic land in Lafayette and Vincennes, IN, in 2023 to determine the impact of different between-row weed control methods on weed suppression and sweetpotato yield. Between-row treatments consisted of organic buckwheat (108 kg ha−1) broadcast seeded immediately after sweetpotato transplanting followed by silage tarping from 3 wk after transplanting (WATr) through harvest, organic buckwheat (108 kg ha−1) broadcast seeded 3 WATr and terminated 7 WATr, and cultivation as a grower standard. Weed density at 6 WATr was 0, 184, and 162 plants m−2 for the silage tarping, living mulch buckwheat, and cultivation treatments, respectively. Total yield was 11,048 kg ha−1 for the living mulch buckwheat, 19,792 kg ha−1 for the cultivation, and 17,814 kg ha−1 for the tarping treatments. Tarping effectively suppressed weeds and produced sweetpotato yields comparable to cultivation, indicating the potential for use by organic growers. When buckwheat was grown between rows 3 to 7 WATr, sweetpotato yield was lower than it was with tarping and cultivation. These results suggest that researchers should be evaluating tarps for small-acreage farmers as a weed management strategy.

Narrow row spacing and layered residual herbicides are recommended for season-long control of herbicide-resistant weeds, but limited research is available to describe interactions between the two practices. The integration of narrow row spacing with layered residual herbicides in herbicide-resistant soybean was evaluated in four site-years. A split-split plot treatment arrangement where the whole plot was soybean trait (LLGT27 or EnlistE3), the subplot was row spacing (38 or 76 cm), and the sub-subplot factor was herbicide program with five treatments: nontreated, preemergence herbicide only (PRE), PRE followed by postemergence (PRE fb POST), PRE fb POST with overlapping residual herbicide (POR), and weed free. Weed control was evaluated through R7 soybean, and weed biomass was collected before POST applications and at R7 soybean. Soybean yield was recorded. Data were subjected to analysis of variance and means separation (α = 0.05). Row spacing had minimal effects on weed control and mixed effects on yield. Waterhemp and Venice mallow control ranged from 83% to 100% 4 weeks after treatment (WAT). POST and POR treatments provided ≥ 94% control of Palmer amaranth 4 WAT; however, PRE resulted in 33% Palmer amaranth control. All treatments resulted in ≥ 95% Palmer amaranth and yellow foxtail control at Scandia during 2021. The greatest income in rainfed site-years was Enlist soybean planted in 76-cm rows with PRE herbicide treatment. The greatest income in the irrigated site-year was with Enlist soybean planted in 38-cm rows with PRE herbicide treatment. Both POST and POR increase weed control compared to PRE, regardless of row spacing in the soybean varieties evaluated, although POR resulted in less income than POST treatments. However, this research did not evaluate weed seed production, which is crucial for long-term weed management and profitability.

Fluridone was registered for use in rice in 2023, offering a new herbicide site of action for growers. However, little information is available on rice tolerance to this herbicide. Field experiments conducted in 2022 and replicated in 2023 near Colt, AR, evaluated the tolerance of twelve rice cultivars to fluridone, applied preemergence or at the 3-leaf growth stage, in separate experiments. Each experiment consisted of one cultivar. Fluridone rates were 0, 168 (1× label rate), and 336 (2× label rate) g ai ha⁻¹ in all experiments. Visible injury varied between years in all experiments, likely due to different environmental conditions. In 2022, injury following preemergence applications of fluridone was below 25% across cultivars. In contrast, in 2023, injury ≥ 30% occurred to five cultivars, with a maximum of 58% observed for the cultivar ‘DG263L’. Across both years, only three cultivars achieved injury ≥ 20% following fluridone applications at the 3-leaf rice. Fluridone negatively affected shoot density, groundcover, chlorophyll content, and days to 50% heading in most cultivars when applied preemergence. When fluridone was applied to 3-leaf rice, at least one of the variables evaluated was negatively affected in two and nine cultivars in 2022 and 2023, respectively. Grain yield reductions of at least 18% were observed in eight cultivars in 2022, and a grain yield decrease from 9% to 49% in eight cultivars occurred in 2023 in the preemergence experiments. Fluridone applied at the 3-leaf rice did not cause a yield penalty to any cultivar in 2022, whereas in 2023, eight cultivars had a yield loss. Yield loss in ‘DG263L’ occurred at the 1× rate in both experiments, indicating this cultivar appears sensitive to fluridone, regardless of the application timing. Based on these findings, fluridone tolerance is cultivar-dependent. Furthermore, preemergence applications of fluridone in rice should be avoided.

Indaziflam was evaluated in Connecticut and Tennessee, USA, for weed control and safety of container-grown ornamental plants. Indaziflam was applied at 49, 98, or 196 g ha-1 to container-grown ornamental plants on an outdoor gravel pad and preemergence or early postemergence to weeds in greenhouse. Ornamental plants were treated twice annually in 2020 and 2021 in Connecticut, and in 2019 and 2020 in Tennessee, with approximately six weeks between applications. Chinese pyramid juniper, common juniper, eastern hemlock, eastern white pine, and Norway spruce in Connecticut, USA, and 'Andorra Compacta’ creeping juniper and 'Black Dragon’ Japanese cedar, ‘Blue Rug’ creeping juniper, and ‘Blue Pfitzer’ Chinese pyramid juniper in Tennessee, USA, were not injured with indaziflam regardless of rate applied. Preemergence application of indaziflam reduced densities of creeping woodsorrel, hairy bittercress, giant foxtail, and large crabgrass 72 to 100%, depending upon the indaziflam rate applied, by 28 d after treatment (DAT). When applied early postemergence, indaziflam provided 97 to 99% control of creeping woodsorrel (1- to 2-leaf), fringed willowherb (4- to 6-leaf), hairy bittercress (cotyledon to 1-leaf), and mouse-ear chickweed (2- to 4-leaf) by 28 DAT. Compared with the nontreated control, the total fresh shoot biomass reduction was 86 to 100% and 78 to 100% following preemergence or postemergence applications. Indaziflam offers a new site-of-action with excellent safety and weed control in the tested ornamental plants.

Pearl millet is a climate-resilient grain and forage crop. Weeds pose a major constraint to its successful production. Limited herbicide options for grass weed control in pearl millet is a serious problem. The objectives of this study were to 1) evaluate the sensitivity of pearl millet parental lines to POST-applied clethodim (136 g ai ha-1), quizalofop-p-ethyl (QPE) (77 ai g ha-1), imazamox (52 g ai ha-1) and nicosulfuron (70 g ai ha-1), and 2) characterize the sensitivity of selected lines to imazamox and nicosulfuron. A total of 56 parental lines were tested. Three lines with low sensitivity to imazamox (ARCH35R, 45R, and 73R), two to nicosulfuron (ARCH45R and 73R), one line with high sensitivity (ARCH21B), and a susceptible sorghum (SOR) hybrid (P84G62) to both herbicides were characterized. All parental lines were sensitive to clethodim and QPE (only four lines showed 2 to 12% survival with 90 to 95% injury at 21 d after application [DAA]). However, all parental lines showed variable sensitivity to imazamox and nicosulfuron (70 to 100% survival with 5 to 70% visible injury and shoot dry biomass reduction at 21 DAA). Dose-response assays revealed that ARCH35R, 45R, and 49R had 7.7 to 12.2 and 3.2- to 12.2-fold reduced sensitivity to imazamox compared to the ARCH21B and SOR, respectively. Similarly, ARCH45R and 49R had 2.5 to 6.0 and 1.5- to 3.7-fold reduced sensitivity to nicosulfuron compared to ARCH21B and SOR, respectively. These findings confirm the first report of reduced sensitivity to imazamox and nicosulfuron among pearl millet lines, suggesting their potential use for in-season grass weed control.

Glufosinate resistance was previously confirmed in three Palmer amaranth accessions from Arkansas (MSR1, MSR2, and CCR). Greenhouse screening results suggested the presence of multiple herbicide resistance. Therefore, this study aimed to determine the postemergence resistance profile of these three glufosinate-resistant Palmer amaranth accessions. Field experiments were also conducted to assess preemergence and postemergence herbicide options to control the accession with the highest glufosinate resistance level (MSR2). A dose-response assay with the three resistant accessions and two susceptible standards was conducted with the herbicides 2,4-D, atrazine, dicamba, diuron, fomesafen, glyphosate, imazethapyr, and mesotrione. The preemergence and postemergence field experiments with MSR2 evaluated 15 and 16 single active ingredients, respectively. The Palmer amaranth accessions that carried glufosinate resistance were also confirmed to be resistant to six other postemergence herbicides: 2,4-D, diuron, fomesafen, glyphosate, imazethapyr, and mesotrione. CCR is also resistant to dicamba. Therefore, accessions MSR1, MSR2, and CCR have evolved resistance to postemergence herbicides pertaining to seven sites of action. A shift toward increased tolerance to atrazine has also been observed among all resistant accessions. Overall, field preemergence treatments with atrazine, pyroxasulfone, or trifludimoxazin obtained the highest MSR2 control levels at all evaluation times and the lowest number of seedlings emerging at 3 and 6 wk after treatment. In the postemergence experiment, only paraquat obtained MSR2 control levels above 90% at all ratings. The lowest number of alive MSR2 plants was observed after postemergence treatments with paraquat or trifludimoxazin. Fields near where glufosinate resistance has been confirmed in Palmer amaranth will likely demand a more diverse and proactive management strategy that relies on combinations of chemical, cultural, and mechanical control tactics. Future efforts should focus on sequential applications and mixture, the elucidation of all resistance mechanisms in the evaluated accessions, and soil-applied dose-response.

A limited number of herbicides and sites of action are registered for use in sugarcane in Louisiana. Repeated use of the same sites of action can lead to the evolution of herbicide resistance in weeds. Therefore, it is critical to evaluate additional sites of action to provide growers with options for rotating herbicides to reduce the risk of resistance. Topramezone, indaziflam, and a formulation including mesotrione, bicyclopyrone, atrazine, and S-metolachlor, along with more common herbicide applications (pendimethalin, and metribuzin, clomazone, and diuron), were evaluated in the spring for injury to sugarcane, weed control, sugarcane yield, and sugar yield. Of these treatments, clomazone applied with diuron was the only herbicide combination to consistently injure the crop, with injury estimates ranging from 11 to 36%, which frequently resulted in reduced sugar yield with losses between 2.3% to 24.1% of the non-treated control. In most treatments, an increase in itchgrass counts was observed between harvests, indicating that additional control strategies will be needed in fields infested with this weed. However, topramezone alone and with triclopyr was well tolerated by sugarcane, with injuries ranging from 0 to 11% two weeks after treatment. Indaziflam and combined application of mesotrione, bicyclopyrone, atrazine, and S-metolachlor injury was at or under 10% two weeks after treatment. The tolerance of sugarcane for these herbicides suggests that they can be incorporated into weed management strategies in sugarcane. These herbicides would increase the sites of action available to be applied in sugarcane and help mitigate the risk of herbicide-resistant weeds.

The windmill palm is a distinctive outdoor ornamental palm adapted to cooler climates. Weeds pose significant challenges in palm nurseries, particularly during seedling and establishment stages. This research was conducted in a nursery with 5,500 windmill palm seedlings, starting in April 2014, when the palm trees were 3 yr old. Experiments were terminated in October 2018 when weed control was no longer necessary due to the advanced growth of the palm trees. The objectives of this study were to determine the weed composition and diversity, elucidate the effects of mechanical weed management (MWM) on growth rate of palm, and develop a sustainable program to maximize palm tree growth through effective weed management and soil tillage. Few herbicides are registered for nursery use in Türkiye, thus weed control was performed mechanically using garden hoeing machines between rows and hand hoeing for intrarow strips. The most common and dense weeds were purple nutsedge, annual mercury, and common purslane in summer and autumn, and burning nettle in winter and spring. In 2014, weed densities were 100, 127, and 145 weeds m–2 for MWM, hand-weeding (HW), and nontreated (NT) plots, respectively. Transplanted palm seedlings required at least two, ideally three growing seasons of intensive weed control until the palm tree crowns block sunlight and suppress weed growth. The research indicated that palm trees in the MWM treatment had approximately 84 leaves and a height of 210 cm by October 2018, compared with 54 leaves and a height of 136 cm for HW, and 40 leaves and 100 cm height for NT. These results highlight the critical role of MWM in promoting optimal growth of Chinese windmill palms. Effective and sustainable weed management, combining MWM and HW, is essential for producing high-quality palm trees. The research provides valuable insights for nursery managers and contributes to best practices for cultivating windmill palm trees in similar climatic regions.

Trifludimoxazin is a new PPO-inhibiting herbicide that is being evaluated for the control of small-seeded annual broadleaf weeds and grasses in several crops. Currently, no information is available regarding peanut cultivar response to trifludimoxazin and its utility in peanut weed control systems. Three unique field experiments were conducted and replicated in time from 2019 through 2022 to determine the response of seven peanut cultivars (AU-NPL 17; FloRun 331; GA-06G; GA-16HO; GA-18RU; GA-20VHO; and TifNV High O/L) to preemergence (PRE) applications of trifludimoxazin and to determine the efficacy of trifludimoxazin at multiple rates and tank-mixtures with acetochlor, diclosulam, dimethenamid-P, pendimethalin, and S-metolachlor for weed management. Cultivar sensitivities to trifludimoxazin were not observed. Peanut density was not reduced by any trifludimoxazin rate. Trifludimoxazin at 75 g ai ha-1 increased leaf necrosis by 18%, peanut stunting by 10%, and reduced yield by 6% when compared to the non-treated control in 2019. However, this rate only increased leaf necrosis by 4%, stunting by 3% to 5%, and had no negative impact on yield in 2020-2021. Generally, peanut injury from PRE applied trifludimoxazin was similar to or less than that observed from flumioxazin at 2 wk after application (WAA). Peanut yield in the weed control study was reduced 11 to 12% when treated with trifludimoxazin at 150 g ha-1 rate (4X) when compared to the 75 g ha-1 rate. However, yield was not different from the flumioxazin treatment. Palmer amaranth control with trifludimoxazin systems was ≥ 91% at 13 WAA, wild radish control was ≥ 96% at 5 WAA, and annual grass control was ≥ 97% at 13 WAA. Peanut is sufficiently tolerant of 38 g ha-1 of trifludimoxazin and when tank-mixed with other residual herbicides provides weed control similar to flumioxazin-based systems.

Outdoor studies were conducted to determine the extent of leafy spurge biomass reduction resulting from broadcast application of 2,4-D (2,244 g ae ha−1) with and without wiper-applied glyphosate. Glyphosate (575 g ae L−1) was applied at 0%, 33%, 50%, and 75% diluted concentrate with a wiper 24 h after 2,4-D was broadcast-applied. Injury estimates and shoot biomass did not differ between plants treated with 2,4-D only or when glyphosate was wiper-applied 21 d after treatment. Shoot regrowth biomass of plants treated with 2,4-D only was approximately 560% greater than nontreated plants 3 mo after treatment. Plants treated with wiper-applied glyphosate exhibited shoot regrowth biomass of less than 10% compared with nontreated plants 3 mo after treatment. Root biomass of plants treated with 2,4-D only (160% of nontreated plants) exhibited a similar pattern of shoot regrowth biomass. Root biomass of plants treated with wiper-applied glyphosate exhibited approximately 50% reductions compared with nontreated plants. All vegetative metrics were equally reduced with all tested concentrations of glyphosate; therefore, all labeled concentrations should be effective. The results of the experiment indicate that broadcast-applied 2,4-D is more effective at reducing leafy spurge biomass with the addition of wiper-applied glyphosate.

As mid-southern U.S. rice producers continue to adopt furrow-irrigated rice (FIR) 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 two weeks before heading but cover crops did not impact 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 FIR while having a minimal effect on rice establishment and yield.