Herbicide Resistance Management Research Articles

Mechanistic understanding and sustainable management of non-target site herbicide resistance in modern day agriculture

Mechanistic understanding and sustainable management of non-target site herbicide resistance in modern day agriculture

Efficacy of sequential application of herbicide mixture for management of multiple herbicide resistant in Phalaris minor in wheat (Triticum aestivum)

The emergence of multiple herbicide resistance in Phalaris minor is a major threat to wheat (Triticum aestivum L.) production in north-western Indo-Gangetic Plains of India. The present study was carried out during winter (rabi) seasons of 2020–21 and 2021–22 at research farm of Chaudhary Charan Singh Haryana Agricultural University, Hisar, Haryana for management of herbicide resistance in Phalaris minor Retz. in wheat using pre and post-emergence herbicide mixtures with different mode of action. The experiment was laid out in randomized block design (RBD) with 15 treatments, replicated thrice. Sequential application of flumioxazin 125 g/ha with pendimethalin (tank mix) 1500 g/ha fb clodinafop + metribuzin 174 g/ha resulted in significantly lowest weed density, dry matter of P. minor and broad-leaf weeds, and it was statistically comparable to application of flumioxazin alone or as mixture with pendimethalin as pre-emergence; pyraxosulfone + pendimethalin 127.5 + 1500 g/ha fb PoE (post-emergence) application of either mesosulfuron + iodosulfuron 14.4 g/ha; sulfosulfuron + metsulfuron, pinoxaden + metsulfuron 50 + 4 g/ha, clodinafop + metribuzin 174 g/ha, respectively. Phytotoxicity of flumioxazin was observed on wheat after 2–3 days of 1st irrigation i.e. 25 DAS (days after sowing). Application of pyroxasulfone + pendimethalin pre fb PoE mesosulfuron + iodosulfuron resulted in significantly higher grain yield (5847 and 5369 kg/ha, during 2021 and 2022, respectively) as compared to other herbicides.

Acting pre-emptively reduces the long-term costs of managing herbicide resistance

Globally, pesticides improve crop yields but at great environmental cost, and their overuse has caused resistance. This incurs large financial and production losses but, despite this, very diversified farm management that might delay or prevent resistance is uncommon in intensive farming. We asked farmers to design more diversified cropping strategies aimed at controlling herbicide resistance, and estimated resulting weed densities, profits, and yields compared to prevailing practice. Where resistance is low, it is financially viable to diversify pre-emptively; however, once resistance is high, there are financial and production disincentives to adopting diverse rotations. It is therefore as important to manage resistance before it becomes widespread as it is to control it once present. The diverse rotations targeting high resistance used increased herbicide application frequency and volume, contributing to these rotations’ lack of financial viability, and raising concerns about glyphosate resistance. Governments should encourage adoption of diverse rotations in areas without resistance. Where resistance is present, governments may wish to incentivise crop diversification despite the drop in wheat production as it is likely to bring environmental co-benefits. Our research suggests we need long-term, proactive, food security planning and more integrated policy-making across farming, environment, and health arenas.

Current and future glyphosate use in European agriculture

AbstractThere has been a longstanding and contentious debate about the future of glyphosate use in the European Union (EU). In November 2023, the European Commission approved the renewal of the use registration for glyphosate for a further 10 years. Nevertheless, the EU Farm to Fork strategy calls for a 50% reduction in pesticide use by 2030. In November 2022, the European Weed Research Society organised a 2 day workshop to identify critical glyphosate uses in current EU cropping systems and to review the availability of glyphosate alternatives. Workshop participants identified four current, critical uses in EU cropping systems; control and management of perennial weeds, weed control in conservation agriculture, vegetation management in tree and vine crops and herbicide resistance management. There are few herbicide alternatives that provide effective, economic, broad‐spectrum control of weeds, particularly perennial weeds. Mechanical weed control, and in particular, soil cultivation is the most obvious glyphosate alternative. However, this is not possible in conservation agriculture systems and, in general, increased soil cultivation has negative impacts for soil health. Emerging technologies for precision weed control can enable more targeted use of glyphosate, greatly reducing use rates. These technologies also facilitate the use and development of alternative targeted physical weed control (e.g. tillage, lasers, electricity), reducing the energy and environmental costs of these approaches. In tree crops, the use of organic and inorganic mulches can reduce the need for glyphosate use. In general, reduced use of glyphosate will require an even greater focus on integrated weed management to reduce weed establishment in agroecosystems, increase weed management diversity and limit the use of alternative resistance‐prone herbicides.

Herbicide-resistance management: a common pool resource problem?

AbstractHerbicide resistance is often viewed as a complex problem in need of innovative management solutions. Because of the transboundary mobility of many weeds, resistance to herbicides is also viewed as a community-scale issue. Consequently, the idea of greater coordination among resource users—especially growers—is often promoted as a management approach. Recently, scholars have framed herbicide resistance as a commons problem in need of collective action. Specifically, social scientists have explored the utility of adopting bottom-up, community-based approaches to help solve the growing problem of herbicide resistance through a framework for interpreting the commons known as common pool resource theory. This article analyzes how herbicide resistance fits—and fails to fit—within common pool resource theory and offers an updated conceptual framework from which to build future work. We argue that the application of common pool resource theory to herbicide-resistance management is underdeveloped, and approaches based on this theory have shown little success. The relevance of common pool resource theory for informing herbicide-resistance management is less settled than existing scholarship has suggested, and other frameworks for approaching transboundary resource problems—such as co-production of knowledge and participatory action research—warrant consideration.

The social foundations for re-solving herbicide resistance in Canterbury, New Zealand.

Synthetic herbicides have revolutionised agricultural weed control. Herbicide resistance (HR) is a natural process through which weeds evolve to be no longer susceptible to a herbicide. Repeated use of similar herbicides can lead to the proliferation of resistant weed populations, with detrimental on-farm effects. To date, 267 weed species worldwide are resistant to at least one herbicide. Yet, achieving universal uptake of best practice principles to manage HR remains difficult. Historically not a high priority for New Zealand cropping farmers, resistance may be more prevalent than commonly assumed. This article contributes to emerging national management strategies and the international scholarship on the human dimensions of HR. Regarding resistance as a socio-biological challenge, we draw on qualitative social research with agricultural stakeholders in New Zealand's main cropping region to outline important psychosocial preconditions for effective resistance management. Our findings show that these preconditions include: influencing awareness and attitudes, knowledge and skills; approaching HR as a shared responsibility; and supporting long-term and holistic thinking. We conclude that these preconditions form the social foundations for agricultural stakeholders' capacity to enact best practice principles to continuously re-solve HR. This novel framing allows analytical differentiation between the capacity and ability to act, with practical recommendations and future research needing to address both components of effective HR management.

Evolution of Herbicide Resistant Weeds in Agro-ecological Systems

Weed management through herbicides continues to be the most efficient and cost-effective component of integrated weed management (IWM) in crop production systems. However, the current production systems are characterised by intensive, inappropriate use of herbicides along with misapplication which creates selection pressure and leads to the rapid evolution of herbicide resistance in weeds. Currently, there are 511 unique cases of herbicide-resistant weed species globally, involving 266 species and these comprise 153 and 113 dicots and monocots respectively. To date, herbicide resistance has been reported from 96 crops in more than 71 countries. Furthermore, weeds have evolved resistance to 21 of the 31 known sites of herbicide action in different crops. Understanding the mechanisms of herbicide resistance is therefore essential which when coupled with the ecological and management factors that affect herbicide resistance would lead to the development of appropriate, profitable, and sustainable weed management strategies. The review is aimed at the development of herbicide resistance, mechanisms of herbicide resistance, factors that influence the rate of resistance development and management of herbicide resistance by growers.

Molecular Basis of Resistance to Bensulfuron-Methyl in a Smallflower Umbrella Sedge (Cyperus difformis L.) Population from China

Smallflower umbrella sedge (Cyperus difformis L.) is an invasive weed, and infestations of C. difformis are increasing in rice (Oryza sativa L.) fields in China. Bensulfuron-methyl is a widely used sulfonylurea herbicide that inhibits the acetolactate synthase (ALS) enzyme and has been used in recent years for effectively controlling annual weeds in the Cyperaceae family. In this study, a suspected resistant population of C. difformis (BBHY1) was collected from a rice field in Huaiyuan County, Anhui Province, China, that survived treatment with bensulfuron-methyl at the field-recommended rate (FRR). Single-dose tests and whole-plant bioassays confirmed that the BBHY1 population was resistant to bensulfuron-methyl and had evolved a high level of resistance, with a resistance index (RI) of 12.87. Sequencing of the ALS gene revealed a CCT to CAT point mutation at codon 197, which caused a P-to-H substitution in the resistant plants. Analysis of the relative expression of ALS revealed no significant differences between the resistant and susceptible populations. Inhibiting the activity of cytochrome P450s (P450s) or glutathione S-transferases (GSTs) had no significant effect on bensulfuron-methyl resistance. The BBHY1 population exhibited cross-resistance to pyrazosulfuron-ethyl, penoxsulam, and bispyribac-sodium, with RIs ranging from 5.48 to 20.63, but remained susceptible to MCPA sodium, florpyrauxifen-benzyl, and bentazon, with RIs of <1.00. These herbicides could be potentially used as alternatives for controlling resistant populations and managing herbicide resistance in other aggressive weeds in rice fields.

Standing genetic variation fuels rapid evolution of herbicide resistance in blackgrass

Repeated herbicide applications in agricultural fields exert strong selection on weeds such as blackgrass (Alopecurus myosuroides), which is a major threat for temperate climate cereal crops. This inadvertent selection pressure provides an opportunity for investigating the underlying genetic mechanisms and evolutionary processes of rapid adaptation, which can occur both through mutations in the direct targets of herbicides and through changes in other, often metabolic, pathways, known as non-target-site resistance. How much target-site resistance (TSR) relies on de novo mutations vs. standing variation is important for developing strategies to manage herbicide resistance. We first generated a chromosome-level reference genome for A. myosuroides for population genomic studies of herbicide resistance and genome-wide diversity across Europe in this species. Next, through empirical data in the form of highly accurate long-read amplicons of alleles encoding acetyl-CoA carboxylase (ACCase) and acetolactate synthase (ALS) variants, we showed that most populations with resistance due to TSR mutations-23 out of 27 and six out of nine populations for ACCase and ALS, respectively-contained at least two TSR haplotypes, indicating that soft sweeps are the norm. Finally, through forward-in-time simulations, we inferred that TSR is likely to mainly result from standing genetic variation, with only a minor role for de novo mutations.

Herbicide Resistance Management in Rice: Annual Field Survey of California Rice Weeds Helps Establish a Weed Management Decision Framework

The article presents an annual field survey by the University of California as a manner of herbicide resistance management for California rice growers. Submitted weed seed samples are tested against registered herbicides which achieved no control that field season. All labelled herbicide modes of action for each specific weed species were tested and applied according to their respective labels. Analyses of these experiments and survey data from 2015 to 2021 provide an active weed management decision-making framework for growers and a comprehensive overview of herbicide weed management in California rice.

Artificial Intelligence Tools and Techniques to Combat Herbicide Resistant Weeds—A Review

The excessive consumption of herbicides has gradually led to the herbicide resistance weed phenomenon. Managing herbicide resistance weeds can only be explicated by applying high-tech strategies such as artificial intelligence (AI)-based methods. We review here AI-based methods and tools against herbicide-resistant weeds. There are a few commercially available AI-based tools and technologies for controlling weed, as machine learning makes the classification process significantly easy, namely remote sensing, robotics, and spectral analysis. Although AI-based techniques make outstanding improvements against herbicide resistance weeds, there are still limited applications compared to the real potential of the methods due to the challenges. In this review, we identify the need for AI-based weed management against herbicide resistance, comparative evaluation of chemical vs. non-chemical management, advances in remote sensing, and AI technology for weed identification, mapping, and management. We anticipate the ideas will contribute as a forum for establishing and adopting proven AI-based technologies in controlling more weed species across the world.

Managing herbicide resistance doesn't pay - but acting pre-emptively does.

Abstract Globally, herbicides improve crop yields but at great environmental cost, and their overuse has caused herbicide resistance. This incurs large financial and production losses but, despite this, truly integrated weed management that might delay or prevent resistance is uncommon in intensive farming. We asked farmers to design more diversified cropping strategies aimed at controlling resistance. We estimate resulting weed densities, profits, and yields compared to prevailing practice. Where resistance is low, it is financially viable to diversify pre-emptively; however, once resistance is high, there are financial and production disincentives to adopting diverse rotations. It is therefore as important to manage resistance before it becomes widespread as it is to control it once it has evolved. The diverse rotations targeting high resistance used increased herbicide application frequency and volume, contributing to these rotations' lack of financial viability, and raising concerns about glyphosate resistance. Governments should encourage adoption of diverse rotations in areas without resistance. Where resistance is present, governments may wish to incentivise crop diversification despite the drop in wheat production, as the yield loss may eventually occur anyway under current management. Our research suggests we need long-term food security planning and more integrated policy-making across farming, environment, and health arenas.

Characterization of acetolactate synthase gene (ALS) in Echinochloa colona (L.) Link., a hexaploid weed species

Junglerice (Echinochloa colona) is one of the most problematic weed species in rice fields in Colombia. Herbicides inhibitors of the enzyme acetolactate synthase (ALS) have been widely used to control junglerice and other grass species. ALS inhibitors have the highest reports of resistance worldwide, and Colombia has recent reports of ALS resistance in E. colona. The timely and accurate detection of resistance sources is imperative for mitigating and managing herbicide resistance. However, for E. colona there are no published [...]

Herbicide mixtures: interactions and modeling

Mixing herbicides is a common practice in agriculture, to optimize farm management practices, widen the weed control spectrum, enhance application efficiency, and manage herbicide resistance. Interactions between herbicides can occur within the spray tank, on the leaf surface, and/or inside the plant, resulting in physicochemical and physiological interactions. Additive, synergistic, or antagonistic effects can result from these interactions. Given the range in plant response and the potential for negative and positive outcomes for weed management, predicting herbicide interactions before [...]

In-field assessment of EPSPS amplification on fitness cost in mixed glyphosate-resistant and glyphosate-sensitive populations of Palmer amaranth (Amaranthus palmeri)

AbstractComparing fitness of herbicide-resistant and herbicide-susceptible weed biotypes is important for managing herbicide resistance. Previous research suggests there is little to no fitness penalty from amplification of the 5-enolpyruvylshikimate-3-phosphate synthase (EPSPS) gene (a mechanism of glyphosate resistance) in Palmer amaranth (Amaranthus palmeri S. Watson) in controlled studies in the greenhouse or growth chamber. A field study was conducted in North Carolina at three locations naturally infested with A. palmeri to determine vegetative, reproductive, and germination fitness of plants with and without EPSPS amplification grown season-long with cotton (Gossypium hirsutum L.). Seed number was not correlated with EPSPS copy number. However, when plants were binned into two groups, those having an EPSPS copy number ≥2 (relative to reference genes) and those having an EPSPS copy number <2, plant fresh weight and seed number were 1.4 and 1.6 times greater, respectively, for plants with fewer than 2 EPSPS copies. Amaranthus palmeri height and seed germination, and yield of cotton, did not differ when comparing the two binned groups. These data suggest that A. palmeri plants with EPSPS amplification are relatively less fit in the absence of glyphosate, but this reduced fitness does not translate into differences in interference with cotton.

Herbicide-Resistance in Turf Systems: Insights and Options for Managing Complexity

Due to complex interactions between social and ecological systems, herbicide resistance has classic features of a “wicked problem”. Herbicide-resistant (HR) Poa annua poses a risk to sustainably managing U.S. turfgrass systems, but there is scant knowledge to guide its management. Six focus groups were conducted throughout the United States to gain understanding of socio-economic barriers to adopting herbicide-resistance management practices. Professionals from major turfgrass sectors (golf courses, sports fields, lawn care, and seed/sod production) were recruited as focus-group participants. Discussions emphasized challenges of the weed management of turfgrass systems as compared to agronomic crops. This included greater time constraints for managing weeds and more limited chemical control options. Lack of understanding about the proper use of compounds with different modes of action was identified as a threat to sustainable weed management. There were significant regional differences in perceptions of the existence, geographic scope, and social and ecological causes of HR in managing Poa annua. Effective resistance management will require tailoring chemical and non-chemical practices to the specific conditions of different turfgrass sectors and regions. Some participants thought it would be helpful to have multi-year resistance management programs that are both sector- and species-specific.

Occurrence and management of herbicide resistance in annual vegetable production systems in North America

AbstractHerbicide resistance has been studied extensively in agronomic crops across North America but is rarely examined in vegetables. It is widely assumed that the limited number of registered herbicides combined with the adoption of diverse weed management strategies in most vegetable crops effectively inhibits the development of resistance. It is difficult to determine whether resistance is truly less common in vegetable crops or whether the lack of reported cases is due to the lack of resources focused on detection. This review highlights incidences of resistance that are thought to have arisen within vegetable crops. It also includes situations in which herbicide-resistant weeds were likely selected for within agronomic crops but became a problem when vegetables were grown in sequence or in adjacent fields. Occurrence of herbicide resistance can have severe consequences for vegetable growers, and resistance management plans should be adopted to limit selection pressure. This review also highlights resistance management techniques that should slow the development and spread of herbicide resistance in vegetable crops.

Target-site mutation and cytochrome P450s confer resistance to multiple herbicides in Italian ryegrass (Lolium multiflorum Lam.) from China

Italian ryegrass (Lolium multiflorum Lam.) is a highly competitive grass weed capable of severely infesting wheat fields worldwide. In recent years, Chinese farmers are finding it increasingly difficult to control L. multiflorum when using acetyl-CoA carboxylase (ACCase)-inhibiting herbicides. Accordingly, clarifying the resistance pattern of putative resistant populations of L. multiflorum is important for selecting alternative herbicides for effective weed control. In this study, a putative resistant L. multiflorum population, HN-03, which apparently has survived clodinafop-propargyl treatment under the recommended field application rate, was collected from a wheat field in Zhumadian, Henan, China. Whole-plant bioassay revealed that the HN-03 population had evolved high-level resistance to clodinafop-propargyl. Sequencing of the ACCase gene revealed a point mutation, of TGG to TGT, at codon position 1999, causing a Trp-to-Cys substitution in the resistant plants. The HN-03 population also exhibited cross-resistance to fenoxaprop-P-ethyl, clethodim, and pinoxaden and multiple-resistance to mesosulfuron-methyl and bixlozone, but it remained susceptible to cypyrafluone. Pre-treatment with piperonyl butoxide and malathion considerably increased the susceptibility of the HN-03 population to fenoxaprop-P-ethyl and mesosulfuron-methyl, by 25.3% and 36.6%, respectively. This study shows the L. multiflorum population HN-03 has evolved multiple herbicide resistance due to both a target-site mutation and P450s-mediated enhanced metabolism. Cypyrafluone can be used as an alternative herbicide to control resistant L. multiflorum, and it might be potentially helpful for improving the management of herbicide resistance in other aggressive weeds.

The cost of implementing effective herbicide mixtures for resistance management

Background: Mixtures of herbicide sites of action (SOA) are often promoted as an effective practice for proactive herbicide resistance management, but the cost of implementation is less-often considered in these recommendations, especially in the academic literature. Objective: Estimate the costs of implementing herbicide SOA mixtures that are effective for herbicide resistance management under different scenarios involving crops, weed species, and existing resistance. Methods: Using data from the Guide for Weed, Disease, and Insect Management in Nebraska, an optimization function [...]

Emerging weed resistance increases tillage intensity and greenhouse gas emissions in the US corn-soybean cropping system.

Tillage is a common agricultural practice that helps prepare the soil and remove weeds. However, it remains unknown how tillage intensity has evolved and its effect on net greenhouse gas (GHG) emissions. Here, using a process-based modelling approach with a multi-source database, we examined the change in tillage intensity across the US corn-soybean cropping systems during 1998-2016 and the impact of tillage intensity on soil GHG emissions. We found that tillage intensity first decreased and then, after 2008, increased, a trend that is strongly correlated with the adoption of herbicide-tolerant crops and emerging weed resistance. The GHG mitigation benefit (-5.5 ± 4.8 TgCO2e yr-1) of decreasing tillage intensity before 2008 has been more than offset by increased GHG emissions (13.8 ± 5.6 TgCO2e yr-1) due to tillage reintensification under growing pressure of weed resistance. As weed resistance persists or grows, tillage intensity is anticipated to continue rising, probably increasing GHG emissions. Our results imply that farmers' choices in managing herbicide resistance may help mitigate agricultural GHG emissions, underscoring the importance of an alternative strategy to control weeds.