Established hedgerows of native plants on the borders of crop fields provide a variety of ecosystem service benefits in agricultural landscapes. However, their influence on weed communities is not well understood, and there are concerns that hedgerows could contribute to weed infestations on farms. To address this research gap, we examined the role of established hedgerows of native California plants on weed abundance (weed numbers and cover) and weed species richness in field borders and in adjacent crops, in large-scale, monocropping systems compared with conventionally managed field borders (i.e., no hedgerows). Across 20 farm sites in California’s Central Valley, hedgerows on orchard crop borders reduced weed numbers by 66%, weed species richness by 59%, and weed cover by 74%. On annual field crop borders, hedgerows reduced weed numbers by 71%, weed species richness by 60%, and weed cover by 70%. In orchards, hedgerows also reduced weed intrusion into the adjacent crop interior, with significantly lower weed cover to the first tree row (area directly underneath the trees), weed species richness to the 10 m tree row, and weed numbers to the 10 m avenue (area between the tree rows). Yearly management practices and associated costs for weed control in established hedgerows were significantly less than for conventionally managed field borders. This study highlights the effectiveness of native hedgerows as a sustainable nature-based solution for reducing weed pressure and management inputs on farms.

Pot studies outdoors under natural environmental conditions were conducted to determine 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 hrs after 2,4-D was broadcast applied. Injury estimates and shoot biomass did not differ between plants treated with 2,4-D-only or the addition of wiper-applied glyphosate 21 days after treatment. Shoot regrowth biomass of plants treated with 2,4-D-only was approximately 560% greater compared to nontreated plants three months after treatment. Plants treated with wiper-applied glyphosate had shoot regrowth biomass of less than 10% compared to the nontreated plants 3 months after treatment. Root biomass of 2,4-D-only treated plants (160% of nontreated plants) followed a similar pattern of shoot regrowth biomass. Root biomass of plants treated with wiper-applied glyphosate exhibited approximately 50% reductions compared to nontreated plants. The concentrations of glyphosate tested reduced all vegetative metrics equally; therefore, all labeled concentrations should be effective. The results of the experiment show that broadcast-applied 2,4-D is more effective at reducing leafy spurge biomass with the addition of wiper-applied glyphosate.

Weed infestations have been identified as a major cause of yield reductions in rapeseed (Brassica napus L.), a vital oil crop that has gained significant prominence in Iran, especially within Fars Province. Weed management using machine learning algorithms has become a crucial approach within the framework of precision agriculture for enhancing the efficacy and efficiency of weed control strategies. The evolution of habitat suitability models for weeds represents a significant advancement in agricultural technology, offering the capability to predict weed occurrence and proliferation accurately and reliably. This study focuses on the issue of dominant weed infestation in rapeseed cultivation, particularly emphasizing the prevalence and impact of wild oat (Avena fatua L.) as the dominant weed species in rapeseed farming in 2023. We collected data on 12 environmental variables related to topography, climate, and soil properties to develop habitat suitability models. Three “machine learning techniques”, including “random forest (RF)”, “support vector machine (SVM)”, and “boosted regression tree (BRT)”, were estimated based on the “receiver operating characteristic (ROC) and area under the curve (AUC)” to model the distribution of A. fatua. Model performance was quantified using the “ROC curve and AUC” metrics to identify the best predictive algorithm. The findings indicated that “Random Forest (RF), boosted regression tree (BRT), and support vector machine (SVM)” models exhibited accuracies of 99%, 97%, and 96% for the habitat suitability of A. fatua, respectively. The Boruta feature selection method identified the slope variable as significantly influential in wild oat habitat suitability modeling, followed by plan curvature, clay, temperature, and silt. This study serves as a case study that highlights the utility of machine learning for habitat suitability predictions when information on multiple environmental variables is available. This approach supports effective weed management strategies, potentially enhancing rapeseed productivity and mitigating the ecological impacts associated with weed infestation.

Field studies were conducted in North Carolina to determine the critical period of weed control (CPWC) for Italian ryegrass in winter wheat. Soft red winter wheat was planted in late fall in 2017 and 2018 in no-till fields near Salisbury, NC. Treatments consisted of allowing weeds to grow from crop emergence for different intervals until removal (“weedy”), maintaining “weed-free” conditions from crop emergence for the same intervals, and then letting the weeds emerge and compete with the crop for the duration of the season. In 2017, weed removal occurred in two-week intervals from crop emergence up to 18 weeks after crop emergence (WAE) and three-week intervals up to 18 WAE in 2018. Additional biological measurements, including Italian ryegrass density and height, were collected at 6, 12, and 18 WAE to characterize the effect of crop-weed interactions on the CPWC and weed populations. Non-linear regression analysis was conducted to relate the timing of weed removal and yield loss. The analysis was done using growing degree days (GDD) accumulated at corresponding WAE. Italian ryegrass density ranged from 292 to 824 plants m-2, which created intense competitive conditions with wheat. In the absence of weed control, yield loss surpassed 60%. Using 5% yield loss as an accepted threshold, the CPWC for Italian ryegrass in no-till planted wheat was estimated to be from 1100 to 1900 GDD. This relatively short period makes it possible to reduce weed control intensity if control actions are properly timed.

The southern African shrub boneseed [Chrysanthemoides monilifera subsp. monilifera (L.) Norl.] is a perennial shrub that is a significant threat to natural ecosystems and is listed as a Weed of National Significance in Australia. In Western Australia (WA) it has spread across peri-urban and natural environments. We assembled a single standardized database containing more than 2,050 presence records for individual plants and 135 absence records at a local population level. We further refined the populations into 89 sites that require different management trajectories due to topography and capacity of land managers to implement control. Forty-nine of these sites were in urban regions and 40 sites were in regional WA. We split these 89 sites into three near-term management goals: watch (12), extirpate (68), and contain (9). The 12 watch sites are those where all available evidence suggests that there have been no new inputs into the seedbank for 15 yr. The 68 sites marked for extirpation are those where delimitation is already achieved or easily achievable, where there have been minimal seed inputs into the soil seedbank in recent years due to consistent surveillance and control, and where surveys for new plants are likely to be efficient to conduct. Finally, for nine sites in urban regions around Perth, we recommend containment in the near term with a longer-term goal to achieve delimitation and extirpation. To achieve the objective of state-level eradication, a coordinated and sustained campaign involving three components—delimitation of all sites, prevention of further inputs into the soil seedbank, and systematic field surveys to remove plants—must commence without delay. While resourcing requirements for delimitation and overall program management are not possible to estimate, our prior experience suggests that it will take at least 1,900 h of on-ground surveying by experienced personnel to achieve extirpation of C. monilifera subsp. monilifera in WA.

There is limited information on the crop safety and weed control potential of commercially available PRE herbicides when applied under plastic mulch on various cucumber and summer squash cultivars grown in Florida. Two cucumber field trials were conducted at the Gulf Coast Research and Education Center in Wimauma, FL, in fall 2021 and spring 2022 to determine the effects of halosulfuron, pendimethalin, S-metolachlor, sulfentrazone, fomesafen, napropamide, oxyfluorfen, and flumioxazin on crop growth and development, yield, and the control of various weed species in the fields. We conducted this trial using three cucumber cultivars: ‘Speedway’, ‘Dominator’, and ‘Mongoose’. Two summer squash field trials were conducted simultaneously, evaluating all the mentioned herbicides, except flumioxazin, in addition to rimsulfuron on three summer squash cultivars: ‘Spineless Beauty’, ‘Payload’, and ‘Everglade’. In the cucumber trials, crop damage varied with cultivar and ranged from 3% to 16% in fall 2021. All herbicides caused ≥10% crop injury, except oxyfluorfen and flumioxazin, at 28 d after transplanting (DATr) in spring 2022. In the summer squash trial, halosulfuron, S-metolachor, and flumioxazin were the three most injurious PRE herbicides, causing more than 10% crop injury in seed-grown summer squash, with no effect of PRE herbicides on crop injury in transplant-grown summer squash in fall 2021. In spring 2022, crop injury with PRE herbicides varied with cultivar, where pendimethalin and S-metolachlor were consistently the most injurious PRE herbicides, causing 14% to 25% injury at 28 DATr. All PRE herbicides caused some damage to cucumber and summer squash, with limited differences between cultivars and no effect on overall crop yield.

Herbicides have been placed in global Herbicide Resistance Action Committee (HRAC) herbicide groups based on their sites of action (e.g., acetolactate synthase–inhibiting herbicides are grouped in HRAC Group 2). A major driving force for this classification system is that growers have been encouraged to rotate or mix herbicides from different HRAC groups to delay the evolution of herbicide-resistant weeds, because in theory, all active ingredients within a herbicide group physiologically affect weeds similarly. Although herbicide resistance in weeds has been studied for decades, recent research on the biochemical and molecular basis for resistance has demonstrated that patterns of cross-resistance are usually quite complicated and much more complex than merely stating, for example, a certain weed population is Group 2-resistant. The objective of this review article is to highlight and describe the intricacies associated with the magnitude of herbicide resistance and cross-resistance patterns that have resulted from myriad target-site and non–target site resistance mechanisms in weeds, as well as environmental and application timing influences. Our hope is this review will provide opportunities for students, growers, agronomists, ag retailers, regulatory personnel, and research scientists to better understand and realize that herbicide resistance in weeds is far more complicated than previously considered when based solely on HRAC groups. Furthermore, a comprehensive understanding of cross-resistance patterns among weed species and populations may assist in managing herbicide-resistant biotypes in the short term by providing growers with previously unconsidered effective control options. This knowledge may also inform agrochemical company efforts aimed at developing new resistance-breaking chemistries and herbicide mixtures. However, in the long term, nonchemical management strategies, including cultural, mechanical, and biological weed management tactics, must also be implemented to prevent or delay increasingly problematic issues with weed resistance to current and future herbicides.

Alternative strategies to fumigation are needed to manage weeds and improve strawberry fruit yield in annual hill plasticulture production systems. Field experiments were conducted in Blackstone, VA, for two consecutive growing seasons, 2013/14 and 2014/15, to assess the efficacy of 4 wk and 8 wk soil solarization (SS) and application of mustard seed meal (MSM) at 1,121 kg ha−1, alone and in combination, for weed control efficacy and crop yield estimation in this production system. These treatments were compared to the use of 1,3-dichloropropene (1,3-D) + chloropicrin (Pic) as a fumigation standard at 188 kg ha−1 and an untreated control (UTC). Over both growing seasons, compared to 1,3-D+ Pic, the SS-MSM-8wk and SS-8wk treatments provided equivalent or reduced cumulative weed count, including weed count of several dominant weed species such as annual ryegrass, speedwell, common chickweed, and cudweed. The SS-4wk and MSM-4wk treatments did not affect weed density compared with the UTC. The MSM-8 wk and 4-wk treatments reduced cumulative weed counts over that of the UTC. In the second growing season, the total yield was significantly higher after the 1,3-D + Pic fumigation treatment compared with yield after other treatments. The SS-4wk, MSM-4wk, and MSM-8wk treatments did not improve the total or marketable yield compared with the UTC. The marketable yield after the SS-MSM-8wk treatment was similar to that of the 1,3-D + Pic treatment. In conclusion, the SS-8wk and SS-MSM-8wk treatments may be effective weed management strategies for organic growers, small farms, or growers who cannot use chemical fumigants due to new regulations and potential risks to human health.

Fast and efficient identification is critical for reducing the likelihood of weed establishment and for appropriately managing established weeds. Traditional identification tools require either knowledge of technical morphological terminology or time-consuming image matching by the user. In recent years, deep learning computer vision models have become mature enough to enable automatic identification. The major remaining bottlenecks are the availability of a sufficient number of high-quality, reliably identified training images and the user-friendly, mobile operationalization of the technology. Here, we present the first weed identification and reporting app and website for all of Australia. It includes an image classification model covering more than 400 species of weeds and some Australian native relatives, with a focus on emerging biosecurity threats and spreading weeds that can still be eradicated or contained. It links the user to additional information provided by state and territory governments, flags species that are locally reportable or notifiable, and allows the creation of observation records in a central database. State and local weed officers can create notification profiles to be alerted of relevant weed observations in their area. We discuss the background of the WeedScan project, the approach taken in design and software development, the photo library used for training the WeedScan image classifier, the model itself and its accuracy, and technical challenges and how these were overcome.

Field experiments were conducted at Clayton and Rocky Mount, NC, during summer 2020 to determine the growth and fecundity of Palmer amaranth plants that survived glufosinate with and without grass competition in cotton. Glufosinate (590 g ai ha−1) was applied to Palmer amaranth early postemergence (5 cm tall), mid-postemergence (7 to 10 cm tall), and late postemergence (>10 cm tall) and at orthogonal combinations of those timings. Nontreated Palmer amaranth was grown in weedy, weed-free in-crop (WFIC) and weed-free fallow (WFNC) conditions for comparisons. Palmer amaranth control decreased as larger plants were treated; no plants survived the sequential glufosinate applications in both experiments. The apical and circumferential growth of Palmer amaranth surviving glufosinate treatments was reduced by more than 44% compared to the WFIC and WFNC Palmer amaranth in both experiments. The biomass of Palmer amaranth plants surviving glufosinate was reduced by more than 62% when compared with the WFIC and WFNC in all experiments. The fecundity of Palmer amaranth surviving glufosinate treatments was reduced by more than 73% compared to WFNC Palmer amaranth in all experiments. Remarkably, the plants that survived glufosinate were fecund as WFIC plants only in the Grass Competition experiment. The results prove that despite decreased vegetative growth of Palmer amaranth surviving glufosinate treatment, plants remain fecund and can be fecund as nontreated plants in cotton. These results suggest that a glufosinate-treated grass weed may not have a significant interspecific competition effect on Palmer amaranth that survives glufosinate. Glufosinate should be applied to 5 to 7 cm Palmer amaranth to cease vegetative and reproductive capacities.

Flumioxazin and S-metolachlor are widely used in conventional sweetpotato production in North Carolina and other states; however, some growers have recently expressed concerns about potential effects of these herbicides on sweetpotato yield and quality. Previous research indicates that activated charcoal has the potential to reduce herbicide injury. Field studies were conducted in 2021 and 2022 to determine whether flumioxazin applied preplant and S-metolachlor applied before and after transplanting negatively affect sweetpotato yield and quality when activated charcoal is applied with transplant water. The studies evaluated five herbicide treatments and two activated charcoal treatments. Herbicide treatments included two flumioxazin rates, one S-metolachlor rate applied immediately before and immediately after transplanting, and no herbicide. Charcoal treatments consisted of activated charcoal applied at 9 kg ha−1, and no charcoal. No visual injury from herbicides or charcoal was observed. Likewise, no effect of herbicide or charcoal treatment on no. 1, marketable (sum of no. 1 and jumbo grades), or total yield (sum of canner, no. 1, and jumbo grades) was observed. Additionally, shape analysis conducted on calculated length-to-width ratio (LWR) for no. 1 sweetpotato roots found no effect from flumioxazin at either rate on sweetpotato root shape. However, both S-metolachlor treatments resulted in lower LWR of no. 1 sweetpotato roots in 2021. Results are consistent with prior research and indicate that flumioxazin and S-metolachlor are safe for continued use on sweetpotato at registered rates.

Mixing ammonium sulfate (AMS) can increase dicamba volatility. Therefore, AMS cannot be used with dicamba products in dicamba-resistant soybean. However, most dicamba products applied in corn are labeled to mix with AMS. The objectives of this study were to evaluate broadleaf weed control with dicamba (DiFlexx®) and dicamba/tembotrione (DiFlexx® DUO) applied alone or with AMS or AMS substitute and their effect on broadleaf weed density and biomass. Field experiments were conducted in Illinois, Missouri, and Nebraska in 2018 and 2019. In Illinois and Nebraska, mixing AMS + crop oil concentrate (COC) with dicamba applied at 1,120 g ae ha−1 increased the control of Palmer amaranth and waterhemp (Amaranthus species) from 78% to 92% and velvetleaf from 73% to 96% compared with dicamba applied alone 14 d after application (DAA); however, Missouri data showed no difference. Mixing AMS + COC with dicamba/tembotrione at 597 and 746 g ai ha−1 did not improve broadleaf weed control 14 DAA at any site compared with dicamba/tembotrione applied alone. Control of Amaranthus species was increased from 82% with dicamba applied at 840 g ae ha−1 to 96% when mixed with AMS + COC 28 DAA in Illinois; however, control was similar to dicamba applied at 1,120 g ae ha−1. Broadleaf weed control did not differ among dicamba or dicamba/tembotrione 28 and 56 DAA in Missouri and Nebraska. Broadleaf weed density decreased from 64 plants m−2 to 24 plants m−2 with dicamba at 1,120 g ae ha−1 with AMS + COC 14 DAA in Nebraska; however, no differences were observed in broadleaf weed density or biomass 56 DAA in any state. The results suggest that dicamba or dicamba/tembotrione can be applied without AMS or AMS substitute, especially at higher rates, without losing broadleaf weed control efficacy.

Field experiments were conducted at Clayton and Rocky Mount, North Carolina, during the summer of 2020 to determine the growth and fecundity of Palmer amaranth plants that survived glufosinate with and without grass competition in soybean crops. Glufosinate (590 g ai ha−1) was applied at early postemergence (when Palmer amaranth plants were 5 cm tall), mid-postemergence (7–10 cm), and late postemergence (>10 cm) and at orthogonal combinations of those timings. Nontreated Palmer amaranth was grown in weedy (i.e., intraspecific and grass competition), weed-free in-crop (WFIC), and weed-free fallow (WFNC) conditions for comparisons. No Palmer amaranth plants survived the sequential glufosinate applications and control decreased as the plants were treated at a larger size in both experiments. The apical and circumferential growth rate of Palmer amaranth surviving glufosinate was reduced by more than 44% compared with the WFNC Palmer amaranth. The biomass of Palmer amaranth plants that survived glufosinate was reduced by more than 87% compared with the WFNC Palmer amaranth. The fecundity of Palmer amaranth that survived glufosinate was reduced by more than 70% compared with WFNC Palmer amaranth. Palmer amaranth plants that survived glufosinate were as fecund as the WFIC Palmer amaranth in both experiments in soybean fields. The results prove that despite the significant vegetative growth rate decrease of Palmer amaranth that survived glufosinate, plants can be as fecund as nontreated plants. The trends in growth and fecundity of Palmer amaranth that survives glufosinate with and without grass competition were similar. These results suggest that glufosinate-treated grass weeds may not reduce the growth or fecundity of Palmer amaranth that survives glufosinate.

Wild oat is a long-standing weed problem in Australian grain cropping systems, potentially reducing the yield and quality of winter grain crops significantly. The effective management of wild oat requires an integrated approach comprising diverse control techniques that suit specific crops and cropping situations. This research aimed to construct and validate a bioeconomic model that enables the simulation and integration of weed control technologies for wild oat in grain production systems. The Avena spp. integrated management (AIM) model was developed with a simple interface to provide outputs of biological and economic data (crop yields, weed control costs, emerged weeds, weed seedbank, gross margins) on wild oat management data in a cropping rotation. Uniquely, AIM was validated against real-world data on wild oat management in a wheat and sorghum cropping rotation, where the model was able to reproduce the patterns of wild oat population changes as influenced by weed control and agronomic practices. Correlation coefficients for 12 comparison scenarios ranged between 0.55 and 0.96. With accurate parameterization, AIM is thus able to make useful predictions of the effectiveness of individual and integrated weed management tactics for wild oat control in grain cropping systems.

Soil amelioration via strategic deep tillage is occasionally utilized within conservation tillage systems to alleviate soil constraints, but its impact on weed seed burial and subsequent growth within the agronomic system is poorly understood. This study assessed the effects of different strategic deep-tillage practices, including soil loosening (deep ripping), soil mixing (rotary spading), or soil inversion (moldboard plow), on weed seed burial and subsequent weed growth, compared with a no-till control. The tillage practices were applied in 2019 at Yerecoin and Darkan, WA, and data on weed seed burial and growth were collected during the following 3-yr winter crop rotation (2019 to 2021). Soil inversion buried 89% of rigid ryegrass (Lolium rigidum Gaudin) and ripgut brome (Bromus diandrus Roth) seeds to a depth of 10 to 20 cm at both sites, while soil loosening and mixing left between 31% and 91% of the seeds in the top 0 to 10 cm of soil, with broad variation between sites. Few seeds were buried beyond 20 cm despite tillage working depths exceeding 30 cm at both sites. Soil inversion reduced the density of L. rigidum to <1 plant m−2 for 3 yr after strategic tillage. Bromus diandrus density was initially reduced to 0 to 1 plant m−2 by soil inversion, but increased to 4 plants m−2 at Yerecoin in 2020 and 147 plants at Darkan in 2021. Soil loosening or mixing did not consistently decrease weed density. The field data were used to parameterize a model that predicted weed density following strategic tillage with greater accuracy for soil inversion than for loosening or mixing. The findings provide important insights into the effects of strategic deep tillage on weed management in conservational agricultural systems and demonstrate the potential of models for optimizing weed management strategies.

Globe artichoke [Cynara cardunculus L. var. scolymus (L.) Fiori] is one of the most important crops across the Mediterranean basin, where weeds are an important biotic constraint limiting crop yields. However, the effects of globe artichoke–cropping systems on weeds have been rarely tested. Following the demand for eco-friendly weed management practices, a multi-location trial (13 farms) was carried out, measuring weed seedbanks and aboveground communities within four globe artichoke–cropping systems: globe artichoke monoculture (ART), past cultivation of globe artichoke (8 to 10 yr ago) (past-ART), a globe artichoke–durum wheat (Triticum durum Desf.) rotation (ART-WHEAT), and a control where globe artichoke was never grown. Both below- and aboveground weed communities were dominated by annual therophytes, but a low correspondence was found between both types of communities. Averaged over farms, ART highly reduced both the weed soil seedbank (1,600 seeds m−2 on average) and the aboveground weed biomass (only 3.4 g dry weight m−2) compared with the control, with a decrease of 72% in the soil seedbank and 99% in the aboveground flora. Moreover, on the farms where globe artichoke was previously grown, a very low aboveground weed biomass (77% less than control) was found. In addition, ART contributed to the preservation of high levels of weed diversity (except for aboveground communities) and therefore avoided the creation of a specialized weed flora. In conclusion, we suggest the inclusion of globe artichoke into crop rotation schemes in Mediterranean agroecosystems as a sustainable tool for reducing both the soil weed seedbank and aboveground weeds, thus reducing the requirement of direct weed control methods and preserving the environment.

Recently, there has been emphasis on the need to shift away from the use of synthetic chemical herbicides to low-risk alternatives derived from natural sources. This is aimed at lowering or averting the negative impact synthetic herbicides have on the environment and dealing with the emergence of weed species resistant to these chemicals. As a result, more stringent measures or outright bans on the use of most synthetic herbicides have been put in place by regulatory bodies. As seaweeds are abundant resources in the marine environment that have the capacity to produce diverse bioactive compounds, they could serve as sustainably viable, natural, and low-risk alternatives/sources to explore for potential phytotoxic capabilities. This could in turn help to enhance or boost the availability of effective solutions in the global bioherbicide market. This review highlights the prospects of using seaweeds as novel biopesticides for the control and management of various plant pests, including weed species, and for the development of sustainable agriculture/forestry practices. More specifically, it focuses on their use as a rich natural source for novel bioherbicide development, a potential that has remained underexplored for many years. However, to unlock the full potential of seaweed-derived bioherbicides and to create a potential path toward their development, increased research and development efforts are urgently needed to tackle and overcome possible constraints posed in this novel area, such as variability in seaweed chemical composition, formulation technologies, stability and efficacy of seaweed bioactive compounds, cost and scalability, and environmental considerations.

Knotroot foxtail has become more prevalent and problematic in pastures and hayfields in the southeastern United States. Gaps exist in our knowledge of which herbicide practices are best for managing this species in bermudagrass forage production. This study was conducted to determine the efficacy of various ways to control knotroot foxtail in bermudagrass with herbicide applications in autumn, postemergence (POST), with and without also applying a herbicide in preemergence (PRE), in spring. The study was a randomized complete block with a factorial arrangement of treatments and included a nontreated control for both fall and spring timings. Glyphosate at two rates (0.35 or 0.7 kg ae ha−1), nicosulfuron (0.07 kg ai ha−1) + metsulfuron (0.012 kg ai ha−1), and hexazinone (1.3 kg ai ha−1) were applied alone in the fall or followed by indaziflam (0.067 kg ai ha−1) or pendimethalin (4.46 kg ai ha−1) in the spring. Three harvests were conducted throughout the growing season to evaluate weed species (knotroot foxtail, large crabgrass, and horsenettle) and bermudagrass biomass as well as overall species composition. The combination of fall and spring treatments did not affect weed species or bermudagrass biomass. Therefore, treatment main effects were analyzed by fall or spring application timing. A spring application of either pendimethalin or indaziflam increased bermudagrass biomass compared with that of the nontreated control. However, neither PRE herbicide effectively reduced knotroot foxtail biomass compared with the nontreated control, although pendimethalin did reduce season-long knotroot foxtail composition. Spring PRE herbicides are an effective tool for forage producers, but further research is needed to identify effective herbicides and additional approaches for the control of knotroot foxtail.

This study investigated replicating six generations of glasshouse-based flowering date selection in wild radish (Raphanus raphanistrum L.) using an adaptation of the population model SOMER (Spatial Orientated Modelling of Evolutionary Resistance). This individual-based model was chosen because it could be altered to contain varying numbers of genes, along with varying levels of environmental influence on the phenotype (namely the heritability). Accurate replication of six generations of genetic change that had occurred in a previous glasshouse-based selection was achieved, without intermediate adjustments. This study found that multiple copies of just two genes were required to reproduce the polygenic flowering time adaptations demonstrated in that previous research. The model included major effect type M1 genes, with linkage and crossing over, and minor effect type M2 genes undergoing independent assortment. Within the model, transmissibility (heritability of each gene type) was parameterized at 0.60 for the M1 genes and 0.45 for the M2 genes. The serviceable parameterization of the genetics of flowering in R. raphanistrum within a population model means that simulated examinations of the effects of external weed control on flowering time adaptations are now more feasible. An accurate and simplified Mendelian-based model replicating the adaptive shifts of flowering time that is controlled by a complex array of genes is useful in predicting life-cycle adaptations to evade weed control measures such as harvest weed seed control, which apply intense adaptive selections on traits that affect seed retention at harvest, including flowering time.

The herbicides that inhibit very-long-chain fatty acid (VLCFA) elongases are primarily used for residual weed control in corn, barley, oat, sorghum, soybean, sugarcane, certain vegetable crops, and wheat production fields in the United States. They act primarily by inhibiting shoot development of susceptible species, preventing weed emergence and growth. The objectives of this review were to summarize 1) the chemical family of VLCFA-inhibiting herbicides and their use in the United States, 2) the VLCFA biosynthesis in plants and their site of action, 3) VLCFA-inhibitor resistant weeds and their mechanism of resistance, and 4) the future of VLCFA-inhibiting herbicides. After their reclassification as Group 15 herbicides to include shoot growth-inhibiting herbicides (Group 8), the VLCFA-inhibiting herbicides are currently represented by eight chemical families (benzofurans, thiocarbamates, α-chloroacetamides, α-oxyacetamides, azolyl-carboxamides, isoxazolines, α-thioacetamides, and oxiranes). On average, VLCFA-inhibiting herbicides are applied once a year to both corn and soybean crops in the United States with acetochlor and S-metolachlor being the most used VLCFA-inhibiting herbicides in corn and soybean production, respectively. The site of action of Group 15 herbicides results from inhibition of the VLCFA synthase, which is encoded by several fatty acid elongase (FAE1)-like genes in VLCFA elongase complex in an endoplasmic reticulum. The VLCFA synthase is a condensing enzyme, and relies on a conserved, reactive cysteinyl sulfur in its active site that performs a nucleophilic attack on either the natural substrate (fatty acyl-CoA) or the herbicide. As of August 2023, 13 weed species have been documented to be resistant to VLCFA inhibitors, including 11 monocot weeds and two dicot weeds (Palmer amaranth and waterhemp). The isoxazolines (pyroxasulfone and fenoxasulfone) are the most recently (2014) discovered VLCFA-inhibiting herbicides. Although the intensity of VLCFA-inhibitor-directed discovery efforts has decreased over the past decade, this biochemical pathway remains a viable mechanistic target for the discovery of herbicide premixes and a valuable component of them.