In plasticulture production, smart spray technology can detect weeds and apply herbicides only where needed in the area between raised, plastic-covered beds (row middle). This technology has the potential to reduce herbicide use and lower input costs. A prototype smart spray system was developed at the Gulf Coast Research and Education Center (GCREC) in Wimauma, FL, that utilizes YOLO-V3 convolutional neural networks to differentiate broadleaf, grass, and nutsedge weeds in row middles. Two sets of field experiments were conducted to determine the efficacy of smart spray technology using a combination of preemergence (PRE) and postemergence (POST) herbicides. All treatments reduced weed density, and targeted applications were as effective as banded treatments. Overall, including a PRE herbicide tended to lower weed density compared to POST applications alone, regardless of application technique. Two banded PRE herbicide applications and two targeted POST applications reduced herbicide use by 52% and 13% compared to banded PRE and POST applications in Experiments 1 and 2, respectively. The reduction from two to one PRE-herbicide applications did not result in an overall herbicide use or cost reduction in Experiment 1, as the decrease in PRE herbicides resulted in increased POST-herbicide usage. In the absence of a banded PRE application, targeted compared to banded POST applications, herbicide usage was reduced by 40 to 67% in Experiment 1 and 79 to 84% in Experiment 2. Smart spray technology is an effective weed management tool for row middles in plasticulture production systems with or without PRE-herbicide applications.

Florpyrauxifen-benzyl is a postemergence (POST) rice herbicide that has reduced rice yield in some situations, and producers are concerned that the impact could be even greater with low rice seeding densities. Therefore, research was conducted in Stoneville, MS, from 2019 to 2021 to evaluate the effect of florpyrauxifen-benzyl on rice yield when a hybrid was seeded at reduced densities. Hybrid rice ‘RT 7521 FP’ was seeded at 10, 17, 24, 30, and 37 kg ha-1. At the four-leaf to one-tiller growth stage, florpyrauxifen-benzyl was applied at 0 or 59 g ai ha-1. Rice injury following the application of florpyrauxifen-benzyl was ≤ 8% across all seeding rates and evaluation intervals. Application of florpyrauxifen-benzyl reduced plant heights by 14% across all seeding rates but did not result in delayed rice maturity. When florpyrauxifen-benzyl was not applied rice in the 10 and 17 kg ha-1 seeding rates, rice matured slower than when seeded at 24, 30, and 37 kg ha-1. When florpyrauxifen-benzyl was applied, rough rice grain yields were reduced by 17 and 37 kg ha-1 but not at any other seeding rate. In conclusion, the application of florpyrauxifen-benzyl at a 2x rate can cause a loss of yield resulting from variation in rice densities.

Commercializing targeted sprayer systems allows producers to reduce herbicide inputs but risks the possibility of not treating emerging weeds. Currently, targeted applications with the John Deere system allow for five spray sensitivity settings, and no published literature discusses the impact of these settings on detecting and spraying weeds of varying species, sizes, and positions in crops. Research was conducted in AR, IL, IN, MS, and NC in 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%, 99.1% to 68.8%, 98.9% to 62.9%, 99.1% to 70.3%, 98.0% to 48.3%, and 98.5% to 55.8% for Convolvulaceae, decumbent broadleaf weeds, Malvaceae, Poaceae, Amaranthaceae, and yellow nutsedge, respectively. Reducing the sensitivity setting reduced the ability to treat weeds. Size of weeds aided targeted application success, with larger weeds being more readily treated through easier detection. Based on these findings, various conditions could impact the outcome of targeted multi-nozzle applications. Additionally, the analyses highlight some of the parameters to consider when using these technologies.

Geyer larkspur is a native perennial forb toxic to cattle. Herbicide control of Geyer larkspur is variable and most likely attributable to the growth stage of the plant when herbicide is applied. The objectives of this study were to (1) evaluate aminopyralid, aminopyralid + florpyrauxifen-benzyl, aminopyralid + 2,4-D, aminopyralid + metsulfuron-methyl, metsulfuron-methyl, triclopyr, and triclopyr + 2,4-D for efficacy in controlling Geyer larkspur; (2) determine if plant growth stage (vegetative or flowering) at the time of herbicide application influences herbicide effectiveness; and (3) determine whether herbicide treatment alters norditerpenoid alkaloid content of Geyer larkspur. Plots were established in eastern Wyoming (2021) and northern Colorado (2022). Herbicide application at the different phenological stages did not affect Geyer larkspur density at the Wyoming site (P = 0.1065; data not shown). Geyer larkspur density at the Wyoming site was reduced by all herbicide treatments 1 year after treatment (YAT) at the vegetative stage and by all herbicides except for triclopyr 2 YAT (P = 0.0249). At the flowering stage, Geyer larkspur density was reduced by all herbicides except metsulfuron-methyl, triclopyr, and triclopyr + 2,4-D at 1 YAT and triclopyr and triclopyr + 2,4-D at 2 YAT. In contrast, there were no differences in Geyer larkspur density across treatments at the Colorado site (P = 0.9621). Precipitation was below average several months prior to herbicide application, which may have affected herbicide effectiveness. The metsulfuron-methyl treatment resulted in the highest total alkaloid concentrations of Geyer larkspur at the vegetative stage and the lowest concentrations at the flowering stage at the Wyoming site. Control efforts of Geyer larkspur in semiarid rangelands can be effectively accomplished with aminopyralid herbicides across vegetative and flowering growth stages provided environmental conditions prior to herbicide application are sufficient for plant growth and uptake of the herbicide.

Introducing new herbicides requires a comprehensive understanding of how crops respond to various herbicide-related factors. Fluridone was registered for rice production in 2023, but research on rice tolerance to this herbicide is lacking. Hence, field research aimed to 1) evaluate the effect of fluridone application timing on rice tolerance and 2) assess rice response to fluridone in a mixture with standard rice herbicides applied to three-leaf rice. Both experiments were conducted in a delay-flooded dry-seeded system using a randomized complete block design, with four replications. Treatments in the first experiment included a nontreated control and ten application timings, ranging from 20 days preplant to postflood. The second experiment had a two-factor factorial structure, with factor A being the presence/absence of fluridone, and factor B being herbicide partners, including bispyribac-sodium, fenoxaprop, penoxsulam, propanil, quinclorac, quizalofop, and saflufenacil. In the first experiment, the maximum injury in 2022 was 28%, caused by the preemergence (PRE) treatment. In 2023, fluridone applied preemergence caused the greatest injury (42%) two weeks after flood establishment, declining to 37% late-season (thirteen days before rice reached 50% heading). Yield reductions of 21% occurred with the delayed-preemergence (DPRE) treatment in 2022 and 42% with the PRE treatment in 2023. Mixing fluridone with standard herbicides increased rice injury by no more than eight percentage points compared to the herbicides alone. Additionally, no adverse effects on rice groundcover or grain yield resulted from fluridone in the mixture. These results indicate a need to avoid fluridone applications near planting because of negative impacts on rice. Furthermore, fluridone can be mixed with commonly used rice herbicides, offering minimal risk to rice.

Japanese stiltgrass is one of the most troublesome invasive weed species in the eastern United States. Strategies for Japanese stiltgrass control in managed lawns are limited since most previous research was conducted in forest understories or golf course natural areas. Eight field experiments were conducted in Virginia from 2014 to 2019 to evaluate the response of Kentucky bluegrass, tall fescue, and Japanese stiltgrass to selective herbicides traditionally marketed for cool-season turfgrass. Only mesotrione-containing treatments transiently injured tall fescue 15 to 25% at 2 wk after treatment (WAT). Fenoxaprop at 35 g ha-1 or higher rates controlled Japanese stiltgrass ≥ 90%, reduced relative cover to <15% compared to nontreated and shoot density to ≤ 6 shoots m-2, respectively, at 8 WAT. Sequential application of topramezone at 3-wk intervals at 27 g ha-1, single application of topramezone at 54 g ha-1 alone or with triclopyr controlled Japanese stiltgrass ≥ 80% and reduced relative weed cover and shoot density to ≤ 22% and < 35 shoots m-2, respectively. Fenoxaprop at 0.25 of the labeled rate for annual grass control in lawns and topramezone-based programs selectively controlled Japanese stiltgrass without injuring tall fescue. Fluazifop at 53 g ha-1 injured Kentucky bluegrass 25% and reduced digitally assessed turf cover by 20% at 4 WAT, but turfgrass recovered by 6 WAT. Reduced rates of fluazifop controlled Japanese stiltgrass 85% and reduced weed shoot density to < 20 shoots m-2 and relative cover to < 20% at 8 WAT. A premix of dicamba, fenoxaprop, and fluroxypyr did not injure Kentucky bluegrass but controlled Japanese stiltgrass ≥ 92% and reduced the relative weed cover and shoot density to ≤ 7% and ≤ 5 shoots m-2, respectively, at 8 WAT. Our research provides herbicide options to practitioners to manage Japanese stiltgrass in Kentucky bluegrass and tall fescue lawns.

Chickpea provides significant diversification benefits for semi-arid cropping systems. However, their slow emergence and open canopy growth habit make them poor competitors against rapidly growing weeds during the early season. In 2022 and 2023, field experiments were conducted at two sites, the Montana State University (MSU) Southern Agricultural Research Center, Huntley, MT, and the MSU Post Agronomy Farm, Bozeman, MT, to evaluate broadleaf weed management by integrating planting date and fall-applied soil-active herbicides in chickpea. Application of dimethenamid at 950 g ai ha-1 + pendimethalin at 1.68 kg ai ha-1, and carfentrazone + sulfentrazone at 238 g ai ha-1 resulted in better protection of yield against weeds and provided longer residual activity for control of kochia, redroot pigweed, and common mallow by reducing weed density to 10 - 20 plants m-2 compared to 50 - 70 plants m-2 in untreated check. Pyridate applied POST (700 g ai ha-1) was required in the above-mentioned treatments to eliminate escaped weeds. Early planting provided an additional biomass reduction compared to late planting due to the crop emergence before or around the same time as the weeds. There was no impact of planting date on weed density and grain yield in plots with dimethenamid + pendimethalin and carfentrazone + sulfentrazone, suggesting that these herbicides can extend the planting date window. These herbicide programs and early planting can be integrated with other weed management tactics for additional weed management options in chickpea.

Water hyacinth is a highly invasive, aquatic species in the southern US that requires intensive management through frequent herbicide applications to minimize harmful impacts. Quantifying management success in large-scale operations is challenging with traditional survey methods, which rely on boat-based teams and can be time-consuming and labor-intensive. In contrast, unmanned aerial systems allow a single operator to survey a waterbody more efficiently and rapidly, enhancing both coverage and data collection. Therefore, the objective of this research was to develop remote sensing techniques to assess herbicide efficacy for water hyacinth control in an outdoor mesocosm study. Experiments were conducted in spring and summer 2023 to compare and correlate data from visual evaluations of herbicide efficacy against nine vegetation indices (VIs) derived from unmanned aerial system (UAS)-based red-green-blue (RGB) imagery. Penoxsulam, carfentrazone, diquat, 2,4-D, florpyrauxifen-benzyl, and glyphosate were applied at two rates, and experimental units were evaluated for six weeks. The Carotenoid Reflectance Index (CRI) had the highest Spearman’s correlation coefficient with visually evaluated efficacy for 2,4-D, diquat, and florpyrauxifen benzyl (> -0.77). The Visible Atmospherically Resistance Index (VARI) had the highest correlation for carfentrazone and penoxsulam treatments (> -0.70), and the EXGR Excess Greenness Minus Redness Index had the highest correlation for glyphosate treatments (> -0.83). CRI had the highest correlation coefficient with the most herbicide treatments, and it was the only VI tested that did not include the red band. These vegetation indices were satisfactory predictors of mid-range visually evaluated herbicide efficacy values but were poorly correlated with extremely low and high values, corresponding to non-treated and necrotic plants. Future research should focus on applying findings to real-world (non-experimental) field conditions and testing imagery with spectral bands beyond the visible range.

Herbicide-resistant weeds demand particular attention in the selection of management strategies, considering the characteristics and fitness differences between susceptible and resistant plants. This study aimed to analyze two heterogeneous junglerice populations, glyphosate-susceptible (EC-S) and glyphosate-resistant (EC-R), derived from field-collected seeds, to quantify the productivity of EC-S and EC-R, to analyze the impact of soybean plants, and to evaluate density dependence. Experiments were conducted in a growth chamber using plastic pots, combining three factors: junglerice density (2, 4, and 8 plants pot⁻¹), the proportion of EC-S and EC-R (100% EC-S, 50% EC-S:50% EC-R, 100% EC-R), and soybean density (0 and 1 plant pot⁻¹). One-leaf junglerice seedling and soybean seeds were planted in plastic pots. After 65 days, plant height (PLH), total number of tillers (TIL), seed number (SEN), and seed weight (SEW) per plant, weight of 100 seeds (HSW), and aboveground dry matter (ADM) were measured. The variables measured were primarily affected by junglerice density and the presence of soybean. Vegetative and reproductive structures of EC-S and EC-R exhibited strongly density-dependent patterns. One soybean plant increased (p<0.05) junglerice productivity at low densities but had no effect at high densities (8 plants pot⁻¹). Mostly EC-S and EC-R showed the same competitive ability. However, EC-S presented a higher index of competitive ability than EC-R in SEN and SEW at lower densities with a soybean plant. A resource complementarity (RYT∼1) between EC-S and EC-R was observed (p<0.05), regardless of the presence of the crop. These results demonstrate that, even in the absence of glyphosate, fitness differences favor heterogeneous resistant populations. This highlights the inherent adaptive advantage of resistant populations and, considering the extensive reliance on glyphosate in current production systems underscores the urgent need for integrated weed management strategies to mitigate the evolution and spread of resistant populations.

Recently a premix of tolpyralate and bromoxynil was registered in the USA and Canada by Corteva Agriscience for weed control in cereals. Limited information exists on weed control efficacy and crop safety with this new herbicide pre-mixture. Greenhouse trials were conducted for two years to test the efficacy of tolpyralate and bromoxynil combinations on 14 broadleaf and 4 grass weeds and crop safety in wheat and barley. Four combinations of tolpyralate and bromoxynil at 1:10 ratio (3.75 + 37.5, 7.5+ 75, 11.25 + 112.5, and 15 + 150 g ai ha-1) as a tank-mix and premix were tested. Stand-alone treatments of tolpyralate and bromoxynil were also included in this study. The lowest tested rate of tolpyralate (3.75 g ha-1) provided 10 to 98% and 27 to 77% control of broadleaf and grass weeds, respectively. Bromoxynil at the lowest tested rate (37.5 g ha-1) provided 16 to 80% and 0 to 30% control of broadleaf and grass weeds, respectively. Tank-mixing these two herbicides at the same rates had improved broadleaf (60 to 100%) and grass (45 to 94%) weed control. The minimum recommended field use rate of tolpyralate +bromoxynil (15 + 150 g ha-1) controlled all the broadleaf weeds >95%. This combination also controlled green foxtail, barnyardgrass and large crabgrass >90%. Additive or synergistic effect between the two herbicides was observed on several broadleaf and grass weed species. Among all the tested weeds, greater synergistic effect was observed on kochia, chickweed, wild mustard, corn poppy, barnyardgrass, green foxtail, and fall panicum. The premix of the two herbicides provided similar broadleaf control, but better grass weed control compared to the tank-mix combinations. Premix was safe on wheat and barley.

Palmer amaranth, a competitive weed in cotton and soybeans, poses challenges due to its rapid growth, high fertility, and herbicide resistance. Effective management strategies targeting sex ratios could reduce seed production by female plants. Protoporphyrinogen oxidase (PPO-) inhibiting herbicides play a role in the evolving resistance of Amaranthus spp. in the Midwestern US. These herbicides may also affect the male-to-female ratio of Palmer amaranth. A two-year field experiment (2015 and 2016) was conducted in a soybean field in Collinsville, Illinois, evaluating various preemergence and postemergence PPO-inhibiting herbicide treatments. Untreated Palmer amaranth populations exhibited a bias towards females. Pre-emergence application of sulfentrazone and flumioxazin effectively reduced Palmer amaranth density (1.66 plants m-2) throughout the season, while post-emergence applications of fomesafen and lactofen provided limited control (27 and 31 plants m-2). Early-season mortality was high (96 %) among Palmer amaranth seedlings, especially with pyroxasulfone+fluthiacet-methyl treatment. Fomesafen increased female biomass (28.8 %) while reducing male biomass compared to non-treated control. In 2015, pyroxasulfone+fluthiacet-methyl and acetochlor altered the male-to-female sex ratio compared to the non-treated control, with pyroxasulfone+fluthiacet-methyl reducing the proportion of females (-0.11 M:F) and acetochlor slightly increasing the proportion of males (0.03 M:F), though not different from a 1:1 ratio. In 2016, pendimethalin and flumioxazin-2 resulted in a strong female-biased sex ratio, with an almost exclusively female population. In both years, the non-treated control plots (-0.58 and -0.55 M:F) maintained a naturally female-biased sex ratio, deviating significantly from a 1:1 ratio. These findings suggest that specific herbicide treatments can alter the sex ratio.. Understanding sex determination in Palmer amaranth holds promise for developing more effective control strategies in the future.

Clethodim is an important herbicide for managing Texas panicum. However, its efficacy is influenced by the weed size and environmental stress during application. Therefore, field and greenhouse studies were conducted in 2023 and 2024 to evaluate clethodim efficacy on various Texas panicum sizes. Clethodim was applied at Texas panicum sizes ranging from 5 cm to 60 cm. A sequential application was applied two weeks after the initial treatment for larger weed sizes (15 to 60 cm). In separate field and greenhouse studies, non-ionic surfactant (NIS), crop oil concentrate (COC), methylated seed oil (MSO), COC + ammonium sulfate (AMS), and MSO + AMS adjuvants were mixed with clethodim to determine efficacy on 10-15 cm and 20-30 cm Texas panicum. In the weed size study, sequential applications of clethodim increased Texas panicum control compared to a single application. At the 10-15 cm growth stage, a single application provided 90% Texas panicum control, whereas the sequential treatment improved control from 76% to 91% at the 15-20 cm growth stage. However, clethodim efficacy declined as Texas panicum size increased across single and sequential treatments. In the adjuvant studies, clethodim plus COC, COC+AMS, or MSO+AMS provided 91%, 93%, and 90% control at the 10-15 cm growth stage, respectively; however, efficacy decreased for 20-30 cm Texas panicum. Texas panicum efficacy was higher for clethodim plus MSO+AMS than clethodim plus MSO; however, AMS did not increase clethodim + COC efficacy. Overall, Texas panicum control with clethodim was most effective when weed height was 15 cm or less. A sequential application of clethodim was required for larger Texas panicum (>15 cm). Clethodim plus COC or MSO+AMS provided the highest control of Texas panicum. This study demonstrated that successful Texas panicum management depends on applying clethodim at the optimum size and selecting the appropriate oil-based adjuvant especially at larger Texas panicum sizes.

Purple witchweed is a hemiparasitic plant that significantly affects sorghum yields in semiarid regions. It also affects crops such as corn, millets, and rice. Developing purple witchweed-resistant sorghum varieties is an essential element in integrated purple witchweed management. This study evaluated the response of 48 sorghum genotypes to purple witchweed grown both in pots and in field conditions. Resistant varieties (Berhan and Framida) and susceptible varieties (Assosa-1, Adukara, and ETSL102967) were used as controls. The findings revealed substantial variability among the sorghum landraces in their response to purple witchweed. Purple witchweed density was less when seeds were grown with early maturing sorghum genotypes, while late-maturing genotypes were more susceptible to the weed. Notably, the ETSL102969 landrace showed strong resistance, comparable to that of Berhan. Additionally, the ETSL102970 landrace demonstrated superior resistance to purple witchweed compared to Framida. Based on these results, ETSL102969 and ETSL102970 are recommended as valuable sources of resistance for breeding programs aiming to improve sorghum resistance against purple witchweed in Ethiopia.

Auxinic herbicides are the second most used in Brazil, often combined with glyphosate in pre-plant burndowns management. However, their efficacy against Benghal dayflower at advanced growth stages remains poorly understood. Two field experiments were conducted in 2021 and 2022 on no-till fields naturally infested with Benghal dayflower at an advanced growth stage (∼50 cm height, 100% soil coverage) to evaluated the control efficacy of 2,4-D at 966 g ae ha-1, triclopyr at 720 g ae ha-1, fluroxypyr at 400 g ae ha-1 and dicamba at 720 g ae ha-1, combined or not with glyphosate (1,550 g ae ha-1). Dicamba was also tested at rates from 288 to 1,008 g ae ha⁻¹. Results indicate Benghal dayflower exhibits variable responses to auxin herbicides, influenced by both chemical family and the herbicide molecule. None of the treatments provided complete control at 8 wk after application (WAA). The highest visible control (∼77%) and dry mass reduction (∼57%) were provided by triclopyr (isolated or combined with glyphosate) and 2,4-D (combined with glyphosate), followed by fluroxypyr (isolated or combined with glyphosate) and 2,4-D (isolated), providing ∼69% visible control and 54% dry mass reduction. Even when statistical differences were detected by adding glyphosate to auxin herbicides, these differences were not sufficient to characterize a synergistic effect or improve control consistency. Dicamba (isolated or combined with glyphosate) provided the lowest control (∼54%) and dry mass reduction (∼30%). Additionally, dicamba doses up to 1008 g ae ha⁻¹ did not provide complete control (∼60% visible control and 51% dry mass reduction), suggesting that dicamba limitations cannot be mitigated through dose increase. By highlighting the challenges in controlling Benghal dayflower at advanced growth stages, these results emphasize the importance of early-stage weed control and the need to carefully assess which auxin herbicides to use and when glyphosate mixtures are necessary.

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 to 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 wk) after crop emergence. The results show 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 to 994 growing degree days (GDD), corresponding to 14 to 85 d after emergence (DAE). These findings emphasize the importance of implementing effective weed control measures from 14 to 85 DAE in the Lower Yangtze Valley to prevent crop losses exceeding a 5% yield loss threshold.

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, and 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 mid-season. The 2024 experiment included a combination treatment of PPI sulfosulfuron, chemigated rimsulfuron, and foliar maleic hydrazide, which resulted in <4 broomrape clusters plot−1. 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.

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 to turf using an RPAAS, focusing on large crabgrass control with quinclorac. The research was conducted in 2022 at two sites in College Station, TX. 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 four-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 to turf. This study also suggests that large crabgrass can be controlled using RPAAS with a range of spray nozzle types at low application volumes to turfgrass. Further research is needed to assess the efficacy of RPAAS-based herbicide applications across a range of herbicides, weed species, and environmental conditions.

Weeds incur up to A$4 billion in economic loss annually to Australian agriculture. Despite this knowledge, few quantitative data exist on yield loss and control costs caused by weeds. This article discusses the economic cost of managing the invasive Navua sedge weed to the grazing and cropping (sugarcane) industries of northern Queensland, Australia, following its introduction into the region in the 1970s. Between 2020 and 2022, through a survey questionnaire distributed to affected farmers, information on control cost, yield loss, and infestation history were documented. Collated data were analyzed using primarily nonparametric statistics due to the skewed or qualitative nature of many of the responses. The weed has invaded farming properties over the past 10 to 20 yr, the infestation level is considered to be low to moderate (median, 22.5%), and it varies appreciably among properties. The median cost of managing Navua sedge was A$72.91/ha when the study was conducted (the current value is now A$82.06). Neither this cost nor the type of management tactics (chemical vs. integrated weed management [IWM]) did not vary between land use types; however, labor, relative to chemical and machinery costs, was the greatest expense. The currently approved herbicide, halosulfuron-methyl (Sempra), is largely ineffective in controlling the weed due to its inability to deplete the weed’s belowground tubers. Correlation analyses suggest that control costs will continue to increase with increasing Navua sedge infestation over time, especially in grazing lands. Farmers are highly aware of the challenge of managing this new weed. Farmers are using a myriad of strategies, including being willing 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.

Cleavers, an annual or winter annual broadleaf weed in the Rubiaceae family, has become troublesome in the wheat fields of the Huang-Huai-Hai region in China due to its herbicide resistance. In North America the common name of the plant is stickwilly; in China it known as cleavers. Four populations of cleavers (JS-15, SD-10, JS-22, and AH-20) were collected from wheat fields in Jiangsu, Shandong, and Anhui provinces, where the plant was not being controlled with applications of florasulam. The aims of this study were to identify the herbicide resistance patterns and investigate the mechanism underlying florasulam resistance. Whole-plant dose-response experiments revealed a notable variation in the degree of resistance exhibited by three specific populations toward florasulam, in comparison to the most sensitive population (S and AH-9), with the highest resistance index reaching 841.4. A gene-sequencing assay for acetolactate synthase (ALS) found that plants that were resistant to ALS from the JS-15, JS-22, and AH-20 populations 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 JS-15, JS-22, and AH-20 plants was greatly resistant to florasulam relative to plants that are susceptible. Additionally, according to the resistance rating system, all resistant populations were susceptible to carfentrazone-ethyl + MCPA-sodium and bipyrazone + fluroxypyr-methyl. AH-20, JS-15, and JS-22 exhibited resistance to selected ALS, 4-hydroxyphenylpyruvate dioxygenase (HPPD), and photosystem II (PS II) complex inhibitors, demonstrating RR and RRR resistance profiles, whereas AH-9 displayed sensitivity to virtually all tested agents. The SD-10 population, on the other hand, exhibited RR and RRR resistance to HPPD and PS II inhibitors, and sensitivity to tribenuron-methyl. These findings indicate that a target site–based mechanism drives resistance to the ALS inhibitor florasulam in populations of cleavers, but nontarget site resistance may also have contributed to resistance, but this was not investigated. Other herbicides with different sites of action were tested and were active against cleavers.

Fall-planted cover crops are becoming popular among growers in the Midwest for various reasons, including their ability to suppress weeds. Cereal rye is the cover crop most often planted 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 glyphosate alternative acetyl-CoA carboxylase (ACCase)-inhibiting herbicides for terminating cereal rye 15 d before soybean planting (DBSP), at soybean planting day (SPD), and 15 d after soybean planting (DASP) and their effect on weed control, density, biomass, soybean plant stand, and soybean grain yield. Field experiments were conducted from 2018 to 2020 at South Central Ag Lab near Clay Center, Nebraska. Cereal rye biomass collected 15 d 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, at the 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 applications of fluazifop-P-butyl, fluazifop-P-butyl/fenoxaprop-P-ethyl, quizalofop-P-ethyl, and glyphosate. Similarly, at the SPD and 15 DASP termination timings, 66% and 31% control of cereal rye, respectively, were recorded after clethodim was used compared with greater than 92% control after other ACCase-inhibitors and glyphosate were used. Palmer amaranth control at the R5 soybean growth stage was 70%, 88%, and 96%, respectively, at 15 DBSP, SPD, and 15 DASP. Soybean yield was reduced to 2,184 kg ha−1 when cereal rye was terminated at 15 DASP compared with 4,566 kg ha−1 when it was terminated at SPD, and 4,460 kg ha−1 at 15 DBSP.