Resistant Weeds Research Articles

Novel phytotoxic compounds from Streptomyces sp. Caat 7-52: a potential bioherbicide against Conyza canadensis.

The rise of herbicide-resistant weeds like Conyza canadensis L. poses a challenge to modern agriculture, driving the need for eco-friendly alternatives. Microbial metabolites from actinobacteria species offer promising weed-control solutions. This study aims to screen and identify an actinobacteria isolate from Brazil's Caatinga biome that produces phytotoxic metabolites and to characterize its compounds. An isolate, named as Caat 7-52, was selected because of its significant phytotoxic effects against Lemna minor L. Phylogenetic analyses using six concatenated genes (gyrB, recA, rpoB, trpB, atpD and 16S rRNA) confirmed Caat 7-52's close relationship to Streptomyces musisoli TBRC 9950T, despite phenotypical differences. Bioassay-directed isolation against L. minor revealed 3-hydroxybenzoic acid and albocycline as phytotoxins, with minimum inhibitory concentrations of 50.00 and 3.12 μg mL-1, respectively. Albocycline analogues were also detected and exhibited moderate phytotoxicity in L. minor. In addition, albocycline effectively inhibited the seed germination of C. canadensis with a minimum inhibitory concentration of 6.25 μg mL-1, marking the first report of albocycline's phytotoxic activity. Direct use of the fermented broth selectively inhibited dicot weeds, offering a sustainable and solvent-free weed management strategy. The discovery of Streptomyces sp. Caat 7-52 and its metabolites, combined with the direct application of fermented broth, represents a significant advancement in sustainable weed control. This bioherbicidal approach offers an environmentally friendly alternative for managing resistant weeds like C. canadensis and supports the broader use of microbial metabolites in integrated pest management programs. © 2025 Society of Chemical Industry.

Preliminary Investigation on Resistance of Beckmannia syzigachne to Clodinafop-Propargyl and Mesosulfuron-Methyl from China

Beckmannia syzigachne is one of the most competitive weeds in winter wheat fields in China. In this study, 120 suspected resistant populations of Beckmannia syzigachne were collected from the Anhui, Hubei, Jiangsu, and Shandong Provinces from 2017 to 2019. In total, 110 populations exhibited different levels of resistance to clodinafop-propargyl, 114 populations expressed different levels of resistance to mesosulfuron-methyl, and 105 populations were resistant to both herbicides at different levels. The resistant weeds were mainly distributed in Anhui and Jiangsu Provinces. The detection results of acetyl coA carboxylase (ACCase) and acetolactate synthase (ALS) genes in the resistant populations indicated that ACCase gene mutations occurred in 97 out of 110 populations resistant to clodinafop-propargyl and ALS gene mutations occurred in 25 out of 114 populations resistant to mesosulfuron-methyl. There were several mutation types, including Ile-1781-Leu, Trp-2027-Cys, Ile-2041-Asn, Ile-2041-Val, Asp-2078-Gly, and Gly-2096-Ala in the ACCase sequence and Pro-197-Ser, Pro-197-Thr, Pro-197-His, Pro-197-Leu, Asp-376-Glu, and Trp-574-Leu in the ALS sequence. Among these mutation types, Pro-197-His, Asp-376-Glu, and Trp-574-Leu in the ALS sequence were the first identified in Beckmannia syzigachne.

In vitro immunotoxic evaluation of herbicides in RAW 264.7 cells

ABSTRACT Weeds are a concern in agriculture and the use of herbicides constitutes an effective, efficient, and economical way to control their growth. Recent discoveries of herbicides are promising for the management of resistant weeds. However, there is a gap in the knowledge of the toxic effects of some herbicides previously reported on immune cells. The present study aimed to examine cellular immunotoxicity of three herbicides (clomazone, glyphosate, and sulfentrazone) after 96 hr incubation utilizing RAW 264.7 BALB/c mouse monocyte/macrophage-like cell line to elucidate the role of some toxicological pathways. Data demonstrated the herbicides clomazone, glyphosate, and sulfentrazone initiated a cytotoxic effect as evidenced by EC50 values of 429.2; 53.7; 866.6 mg/L, respectively. Clomazone and sulfentrazone, at all concentrations, induced excess production of reactive oxygen (ROS) and reactive nitrogen (RNS) free radicals. An immunosuppression was observed in RAW 264.7 cells after incubation with 50 or 100 mg/L glyphosate and 500 or 1000 mg/L sulfentrazone. In addition, all herbicides produced mitochondrial depolarization and decreased tumor necrosis factor-α (TNF-α) levels. This constitutes the first report of the effects of clomazone and sulfentrazone on RAW 264.7 cells, including reduced TNF-α levels, indicating the adverse influence of herbicides on the immune system.

Rapid Detection of Acetolactate Synthetase Inhibitor Resistant Weeds Utilizing Novel Full-Spectrum Imaging and a Hyperparameter-Tuned Convolutional Neural Network (CNN)

Abstract Herbicide-resistant weeds are fast becoming a substantial global problem, causing significant crop losses and food insecurity. Late detection of resistant weeds leads to increasing economic losses. Traditionally, genetic sequencing and herbicide dose-response studies are used to detect herbicide-resistant weeds, but these are expensive and slow processes. To address this problem, an artificial intelligence (AI)-based herbicide-resistant weed identifier program (HRIP) was developed to quickly and accurately distinguish acetolactate synthetase inhibitor (ALS)-resistant from -susceptible common chickweed plants. A regular camera was converted to capture light wavelengths from 300 to 1,100 nm. Full spectrum images from a two-year experiment were used to develop a hyperparameter-tuned convolutional neural network (CNN) model utilizing a “train from scratch” approach. This novel approach exploits the subtle differences in the spectral signature of ALS-resistant and -susceptible common chickweed plants as they react differently to the ALS herbicide treatments. The HRIP was able to identify ALS-resistant common chickweed as early as 72 hours after treatment at an accuracy of 88%. It has broad applicability due to its ability to distinguish ALS-resistant from -susceptible common chickweed plants regardless of the type of ALS herbicide or dose used. Utilizing tools such as the HRIP will allow farmers to make timely interventions to prevent the herbicide-escape plants from completing their life cycle and adding to the weed seedbank.

Herbicide resistance in weeds: Challenges, mechanisms, and integrated approaches: A review

Herbicide resistance in weeds: Challenges, mechanisms, and integrated approaches: A review

Discovery of Triketone-Indazolones as Novel 4-Hydroxyphenylpyruvate Dioxygenase Inhibiting-Based Herbicides.

4-Hydroxyphenylpyruvate dioxygenase (HPPD) is a crucial herbicide target in current research, playing an important role in the comprehensive management of resistant weeds. However, the limited crop selectivity and less effectiveness against grass weeds of many existing HPPD inhibitors, limit their further application. To address these issues, a series of novel HPPD inhibitors with fused ring structures were designed and synthesized by introducing an electron-rich indazolone ring and combining it with the classical triketone pharmacophore structure. The cocrystal structure of representative compound III-7 complexed with Arabidopsis thaliana HPPD (AtHPPD) was obtained at 2.0 Å resolution to guide the optimization of the designed inhibitor. The optimization results showed that 5-(2-hydroxy-6-oxocyclohex-1-ene-1-carbonyl)-1,4-dimethyl-2-(3-(methylthio)phenyl)-1,2-dihydro-3H-indazol-3-one, III-15, was the most active AtHPPD inhibitor, with an IC50 value of 12 nM, nearly 30 times higher efficacy than mesotrione. Greenhouse herbicidal activity tests demonstrated that compound III-15 exhibited excellent herbicidal potency at 30-120 g ai/ha. Notably, it maintained high safety for peanuts even at 120 g ai/ha. Our results showed that compound III-15 is promising as a new candidate HPPD herbicide for use in the peanut fields.

Assessment of 3-Cyanobenzoic Acid as a Possible Herbicide Candidate: Effects on Maize Growth and Photosynthesis

Chemical weed control is a significant agricultural concern, and reliance on a limited range of herbicide action modes has increased resistant weed species, many of which use C4 metabolism. As a result, the identification of novel herbicidal agents with low toxicity targeting C4 plants becomes imperative. An assessment was conducted on the impact of 3-cyanobenzoic acid on the growth and photosynthetic processes of maize (Zea mays), a representative C4 plant, cultivated hydroponically over 14 days. The results showed a significant reduction in plant growth and notable disruptions in gas exchange and chlorophyll a fluorescence due to the application of 3-cyanobenzoic acid, indicating compromised photosynthetic activity. Parameters such as the chlorophyll index, net assimilation (A), stomatal conductance (gs), intercellular CO2 concentration (Ci), maximum effective photochemical efficiency (Fv′/Fm′), photochemical quenching coefficient (qP), quantum yield of photosystem II photochemistry (ϕPSII), and electron transport rate through PSII (ETR) all decreased. The A/PAR curve revealed reductions in the maximum net assimilation rate (Amax) and apparent quantum yield (ϕ), alongside an increased light compensation point (LCP). Moreover, 3-cyanobenzoic acid significantly decreased the carboxylation rates of RuBisCo (Vcmax) and PEPCase (Vpmax), electron transport rate (J), and mesophilic conductance (gm). Overall, 3-cyanobenzoic acid induced substantial changes in plant growth, carboxylative processes, and photochemical activities. The treated plants also exhibited heightened susceptibility to intense light conditions, indicating a significant and potentially adverse impact on their physiological functions. These findings suggest that 3-cyanobenzoic acid or its analogs could be promising for future research targeting photosynthesis.

A Case of One Step Forward and Two Steps Back? An Examination of Herbicide-Resistant Weed Management Using a Simple Agroecosystem Dynamics Model

Global herbicide-resistant weed populations continue rising due to selection pressures exerted by herbicides. Despite this, herbicides continue to be farmers’ preferred weed-control method due to cost and efficiency relative to physical or biological methods. However, weeds developing resistance to herbicides not only challenges crop production but also threatens ecosystem services by disrupting biodiversity, reducing soil health, and impacting water quality. Our objective was to develop a simulation model that captures the feedback between weed population dynamics, agricultural management, profitability, and farmer decision-making processes that interact in unique ways to reinforce herbicide resistance in weeds. After calibration to observed data and evaluation by subject matter experts, we tested alternative agronomic, mechanical, or intensive management strategies to evaluate their impact on weed population dynamics. Results indicated that standalone practices enhanced farm profitability in the short term but lead to substantial adverse ecological outcomes in the long term, indicated by elevated herbicide resistance (e.g., harm to non-target species, disrupting natural ecosystem functions). The most management-intensive test yielded the greatest weed control and farm profit, albeit with elevated residual resistant seed bank levels. We discuss these findings in both developed and developing-nation contexts. Future work requires greater connectivity of farm management and genetic-resistance models that currently remain disconnected mechanistically.

Impacts of Weed Resistance to Glyphosate on Herbicide Commercialization in Brazil

Herbicides are essential tools for the phytosanitary security of agricultural areas, but their excessive use can cause problems in agricultural production systems and have negative impacts on human health and the environment. The objective of this study was to present and discuss the main causes behind the increase in herbicide commercialization in Brazil between 2010 and 2020. Data from the Brazilian pesticide database, provided by the Instituto Brasileiro do Meio Ambiente e dos Recursos Naturais Renováveis (IBAMA), were used. In 2010 and 2020, Brazil sold 157,512 and 329,697 tons of herbicide active ingredients, respectively, representing a 128.1% increase in commercialization over 11 years. Some herbicides, such as clethodim, haloxyfop-methyl, triclopyr, glufosinate, 2,4-D, diclosulam, and flumioxazin, showed increases in sales volumes between 2010 and 2020 of 2672.8%, 896.9%, 953.5%, 290.2%, 233.8%, 561.3%, and 531.6%, respectively, percentages far exceeding the expansion of Brazil’s agricultural area. The primary reason for this sharp increase in herbicide sales was the worsening cases of weeds resistant and tolerant to glyphosate, with species such as Conyza spp., Amaranthus spp., Digitaria insularis, and Eleusine indica standing out. This situation created the necessity of the use of additional herbicides to achieve effective chemical control of these weed species.

Herbicide resistance is complex: a global review of cross-resistance in weeds within herbicide groups

AbstractHerbicides 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.

Characterization of acetolactate synthase genes and resistance mechanisms of multiple herbicide resistant Lolium multiflorum

Combining imidazolinone-tolerant wheat with imazamox presents an effective solution to combat weed resistance. However, Lolium multiflorum, a troublesome resistant weed infesting wheat fields, may have developed resistance to imazamox, and the potential resistance mechanisms are intriguing. In this study, we explored the susceptibility of L. multiflorum to imazamox and investigated the resistance mechanisms, including the contribution of the target enzyme acetolactate synthase (ALS) to resistance and the presence of non-target-site resistance (NTSR). Eight L. multiflorum populations suspected of being resistant to imazamox were collected, and six populations exhibited resistance, ranging from 2.45-fold to 16.32-fold. The LmALS1 gene from susceptible population D3 plants and multiple copies of the LmALS gene (LmALS1, LmALS2, LmALS2α, LmALS3, LmALS3α, LmALS3β) from resistant populations D5 and D8 plants were separately amplified. Two mutations (Pro/Gln197 to Thr, Trp574 to Leu) were found in LmALS1 in the resistant populations. Compared to D3, LmALS1 was overexpressed in D5 but not in D8. The presence of LmALS1 mutants (LmALS1-Thr197 and LmALS1- Leu574), along with LmALS2, LmALS3, and their subunits, contribute to the resistance phenotype by increasing bonding energies, weakening hydrogen bonds, or decreasing protein binding pocket volumes and surface area. Additionally, D5 and D8 populations exhibited multiple resistance (>40-fold) to three other ALS inhibitors: pyroxsulam, flucarbazone-sodium, and mesosulfuron-methyl. Pre-treatment with malathion and 4-chloro-7-nitrobenzoxadiazole (cytochrome P450 monooxygenase and glutathione S-transferase inhibitors respectively) reversed the resistance of the D8 population and partially reversed the resistance of the D5 population to imazamox. This study characterizes ALS genes and extends our knowledge into the ALS resistance mechanisms involved in L. multiflorum. It also deepens our understanding of the complex diversification resistance mechanisms, thereby facilitating advances in weed resistance management strategies in wheat fields.

Surveillance and mapping of tribenuron-methyl-resistant weeds in wheat fields

Tribenuron-methyl (TBM) is among the herbicides that are widely used for controlling broadleaf weeds in wheat fields in Iran due to its low mammalian toxicity and environmental risk, use at low doses, the broad spectrum of weed control, and low price compared to other herbicides. However, wheat farmers’ repeated application and dissatisfaction with the optimal and effective control of the TBM herbicide have led to investigating broadleaf weed resistance in Iranian wheat fields. For this purpose, through a national call in 2018, a total of 240 broadleaf weed populations belonging to 13 species and 7 plant families were collected from 153 wheat fields in 72 counties across 14 provinces suspected to be resistant to the TBM herbicide. Then, a screening test was conducted in a completely randomized design with 5 replications of each biotype using the recommended dose of 25 g a.i. ha− 1 of TBM in the greenhouse. Overall, the results indicated that 124 (51.7%) of the screened populations were resisted to TBM. Specifically, 44 populations (81%) of Sinapis arvensis L., 18 populations (45%) of Malva neglecta Wallr., 25 populations (45%) of Silybum marianum (L.) Gaertn, 2 populations (66.6%) of Ammi majus L., 1 population (50%) of Rapistrum rugosum L., 3 populations (21%) of Descurainia Sophia (L.) Webb ex Prantl, 9 populations (36%) of Vaccaria hispanica Mill., 8 populations (48%) of Galium aparine L., 9 populations (75%) of Melilotus indicus L. According to the Adkins and Maas evaluation, 4 populations (100%) of Raphanus raphanistrum L. were classified as resistant to TBM. This study is the first comprehensive investigation of broadleaf weed resistance to TBM across Iranian wheat fields, providing crucial insights for future herbicide management strategies. Given the high incidence of resistance, continued use of TBM in Iranian wheat fields may lead to increased yield loss and environmental pollution. Additionally, it is necessary to investigate cross-resistance in resistant populations to other ALS-inhibiting herbicides.

How Does Herbicide Resistance Change Farmer’s Weed Management Decisions? Evidence from the Roundup Ready Experiment

Adoption of diverse weed management practices is viewed as essential for slowing the spread of herbicide-resistant (HR) weeds. Yet, adoption of diverse tactics has remained low, while there has been explosive growth of resistant weeds. This study analyzes U.S.-farm-level data to identify factors affecting adoption of diverse weed management practices. This study uses directed acyclic graphs (DAGs) to consider how practice adoption is influenced by different causal pathways between farmer and farm characteristics and farmer awareness of and concern over HR weeds. This study then uses multiple regression analysis to estimate the direct and indirect pathways that influence practice adoption. Respondents relied more heavily on herbicide-based weed control methods than on mechanical or cultural methods. Concern over herbicide resistance increased the number of practices farmers adopted and the percentage of acres where farmers implemented these practices. Practice adoption was negatively associated with increasing levels of farmer risk aversion. Technological optimism—belief that new herbicides would soon be developed to counter HR weeds—discouraged diverse herbicide use practices that combat resistance, but encouraged use of some non-chemical weed control methods. Perceived weed dispersal externalities (from weed mobility) led to more diverse weed management, running counter to hypotheses that greater mobility reduces incentives for individual resistance management.

Isolation and identification of antifungal, antibacterial and nematocide agents from marine bacillus gottheilii MSB1

Pathogenic fungi employ numerous strategies to colonize plants, infect them, reduce crop yield and quality, and cause significant losses in agricultural production. The increasing use of chemical pesticides has led to various ecological and environmental issues, including the emergence of resistant weeds, soil compaction, and water pollution, all negatively impacting agricultural sustainability. Additionally, the extensive development of synthetic fungicides has adverse effects on animal and human health, prompting the exploration of alternative approaches and green strategies for phytopathogen control. Microorganisms living in sponges represent a promising source of novel bioactive secondary metabolites, potentially useful in developing new nematicidal and antimicrobial agents. This study focuses on extracting bioactive compounds from endosymbiotic bacteria associated with the marine sponge Hyrtios erect sp. (collected from NIOF Station, Hurghada, Red Sea, Egypt) using various organic solvents. Bacillus sp. was isolated and identified through 16 S rRNA gene sequencing. The biocidal activity of Bacillus gotheilii MSB1 extracts was screened against plant pathogenic bacteria, fungi, and nematodes. The n-butanol extract showed significant potential as a biological fungicide against Alternaria alternata and Fusarium oxysporum. Both n-hexane and ethyl acetate extracts exhibited negative impacts against the plant pathogenic bacteria Erwinia carotovora and Ralstonia solanacearum, whereas the n-butanol extract had a positive effect. Regarding nematicidal activity, ethyl acetate and n-butanol extracts demonstrated in-vitro activity against the root-knot nematode Meloidogyne incognita, which causes serious vegetable crop diseases, but the n-hexane extract showed no positive effects. The findings suggest that bioactive compounds from endosymbiotic bacteria associated with marine sponges, particularly B. gotheilii MSB1, hold significant potential as alternative biological control agents against plant pathogens. The n-butanol extract, in particular, displayed promising biocidal activities against various plant pathogenic fungi, bacteria, and nematodes. These results support further exploration and development of such bioactive compounds as sustainable, environmentally friendly alternatives to synthetic pesticides and fungicides in agricultural practices.

Performance of Bt cotton evaluated in relation to mulching and weed control measures in northwest India

BackgroundWeed infestation in cotton has been reported to offer severe competition and cause yield reduction to a large extent. Weeding via cultural practices is time consuming, tedious, and expensive due to long duration of cotton crop and regular monsoon rains during cotton production in India. Chemical weed control has been successfully utilized in cotton in the recent past. However, continuous use of similar herbicides leads to resistance in weeds against herbicides. And when sprayed to the field, herbicides not only suppress weeds but leave undesirable residues in the soil that are hazardous to the environment. Therefore, a study was performed at cotton research area at Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana during two consecutive kharif seasons (2020 and 2021) to determine the most suitable and sustainable weed management strategy through the integration of chemical and cultural methods.ResultsMulching with rice straw of 7.5 t ha−1 resulted in significantly higher cotton seed yield (3 189 and 3 084 kg ha−1) and better weed control in comparison to no mulch treatments (2 990 and 2904 kg ha−1) in 2020 and 2021, respectively. Among various weed management levels, the significantly lowest cotton seed yield was recorded in untreated control (1 841 and 1 757 kg·ha−1 during 2020 and 2021, respectively) in comparison to other treatments while all other treatments were statistically at par with each other during both years of crop experimentation.ConclusionMulching with rice straw of 7.5 t·ha−1 along with a pre-emergence application of pendimethalin (active ingredient) at 1.5 kg·ha−1fb (followed by) one hoeings at 45 days after sowing (DAS) and fb glyphosate 2 kg·ha−1 (Shielded spray) at 90 DAS is a viable option for effective control of grassy and broadleaved weeds in Bt cotton in north-west India.

Presumption of Herbicide Resistant Weeds and Yield of Boro Rice as Influenced by Pre- and Post-emergence Herbicides

In Bangladesh, weed infestation is a leading problem in rice cultivation and the sole dependency on post-emergence herbicides is ineffective. Therefore, a field experiment was carried out at the Agronomy Field Laboratory, Bangladesh Agricultural University, Mymensingh from December 2021 to May 2022. The study was done to determine the relative effectiveness of different pre-emergence herbicides and to presume the herbicide-resistant weeds and yield of boro rice as influenced by pre-and post-emergence herbicides. Four rice varieties: BAU dhan3 (V1), BRRI dhan28 (V2), BRRI dhan81 (V3), BRRI dhan96 (V4) and six herbicide managements: Control (H1), Hand Weeding at 30 DAT (H2), Bensulfuron methyl @ 980 g ha-1 (H3), Pretilachlor @ 2 L ha-1 (H4), Carfentrazon ethyl @ 208 mL ha-1 (H5), Ethoxisulfuron @ 200 g ha-1 (H6) were used in a randomized complete block design (RCBD) with three replications. The most dominant weed species in the experimental plots were Echinochloa crussgalli, Scirpus mucronatus, Monochoria hastata, Enhydra fluctuans and Oxalis europaea. This study found Ethoxisulfuron (H6) and Carfentrazon ethyl (H5) were the most effective weed management treatments for weed suppression and grain yield at twice the recommended doses. In this study, the highest grain yield (5.40 t ha-1), straw yield (6.80 t ha-1) and biological yield (12.20 t ha-1) were obtained from BRRI dhan81 (V3) with hand weeding (H2) and highest harvest index (45.60%) were obtained from BAU dhan3 (V1) with Pretilachlor (H4). Therefore, this result is useful for farmers at field level cultivation of boro rice.

Quinclorac-resistant Echinochloa spp. promoted growth and reproduction of Laodelphax striatellus (Hemiptera: Delphacidae) probably by providing more nutrients and stable environment

Rice is an important agricultural crop that faces serious challenges from pathogens, pests, and weeds during growth stages. Meanwhile, these organisms would interact with each other to increase the level of destruction. The previous studies showed that barnyard grass (Echinochloa spp) could be used as a temporary host to increase infestation of small brown planthopper (SBPH, Laodelphax striatellus), which is one of the main polyphagous pests. Herbicides are widely used to control weeds that induce resistance development. However, little is known about the effects of increased weed resistance on insect species. In this study, we investigated the effect of quinclorac-resistant and sensitive biotypes of barnyard grass (Echinochloa crus-galli var. zelayensis; Echinochloa crus-pavonis Schult) and rice plants (Wuyujing 3) on the ecological fitness of SBPH and examined physiological indicators of plants and SBPH to explore the mechanism. Our results showed that the growth and reproduction of SBPH promoted significantly reared on quinclorac-resistant barnyard grass. From the perspectives of oxidative stress response, the activities of peroxidase (POD) increased and the activities of catalase (CAT), mixed-functional oxidase (MFO), and carboxylesterase (CarE) decreased in SBPH reared on resistant barnyard grass. Combined with the increased amino acid contents (threonine, serine, methionine, and alanine) of resistant barnyard grass E. crus-pavonis, we speculate that quinclorac-resistant barnyard grass probably provides SBPH with a more suitable environment, thus increasing the risk of SBPH.

Evaluation of Critical Period of Crop Weed Competition for Enhanced Weed Management and Yield of Summer Pearl Millet

The field experiment was conducted at Instructional farm of Department of Agronomy, Navsari Agriculture University, Navsari during summer season of 2021 to 2023 to study critical crop-weed competition in summer pearl millet. There were 10 treatments comprising of initial weed free periods of 10, 20, 30 and 40 days after sowing (DAS) and weedy 10, 20, 30 and 40 DAS along with weedy till harvest (un-weeded check) and weed free till harvest (weed free check), were replicated thrice in the randomized block design. Results revealed that maintaining a weed-free condition from 20 to 40 DAS significantly increased the yield of pearl millet, whereas the lower yield was recorded when weeds were allowed to grow during this period. The maximum competition between crop and weed was between 20 to 40 DAS, which can be considered as critical period of crop-weed competition. To avoid the yield loss, integrated weed management can effectively overcome the problems of weed shift and development of resistance in weeds and reduce the weed seed bank and manage the weeds below the economic threshold level to avoid any economic loss in summer pearl millet.

Herbicide‐resistant weed management with robots: A weed ecological–economic model

AbstractThe heavy reliance on herbicides for weed control has led to an increase in resistant weeds in the United States. Robotic weed control is emerging as an alternative technology for removing weeds mechanically using artificial intelligence. We develop an integrated weed ecological and economic dynamic (I‐WEED) model to examine the biophysical and economic drivers of adopting robotic weed management and simulate the optimal timing and intensity of robotic adoption within and across growing seasons. We specify a cohort‐based weed growth model that relates yield damages to effective weed density and treats the susceptibility of weeds to herbicides as a renewable resource that can be regenerated by using mechanical weeding robots, due to a fitness cost that makes resistant weeds less prolific. Compared to myopic weed management which ignores resistance development, forward‐looking management leads to earlier adoption of robots and treating robots as complements instead of substitutes to herbicides. This weed management results in adopting fewer robots, deploying robots on a smaller portion of the land, higher profitability, and lower yield loss in the long run, relative to myopic management. Counterintuitively, myopic management leads to a lower resistance level through its higher robot adoption intensity. We also find that a lower level of initial weed seed resistance and/or a higher fitness cost result in a higher level of resistance because they create incentives for farmers to delay the adoption of robotic weed control. Our analysis shows the importance of jointly considering the interactions between weed ecology and economics in analyzing the incentives and effects of robotic weed management on weed resistance.

Evaluation of Postemergence Weed Control Programs in Cotton Without the Addition of Glyphosate

Glyphosate has played an important role in agricultural production systems, especially after the release of glyphosate resistant crops. With increased usage and an overall reliance on chemical control, weed resistance to glyphosate has occurred and is now a major issue. The objective of this research was to investigate weed control levels provided by glufosinate, 2,4-D, and clethodim as an alternative to glyphosate. Multiple POST applications generally provided superior weed control in comparison to a single early-POST application. No programs provided greater than 80% warm-season grass control beginning 21 d after mid-POST application. Applications of glufosinate or glufosinate + 2,4-D fb clethodim + glufosinate, glufosinate + 2,4-D, or clethodim + glufosinate + 2,4-D provided adequate broadleaf weed control throughout the rating period. Although POST-only programs are an option, they are not a sustainable weed control practice. It remains important to incorporate residual herbicides into a weed control program as well as alternative weed control methods.