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A key challenge in the management of populations is to quantify the impact of interventions in the face of environmental and phenotypic variability. However, accurate estimation of the effects of management and environment, in large‐scale ecological research is often limited by the expense of data collection, the inherent trade‐off between quality and quantity, and missing data.In this paper we develop a novel modelling framework, and demographically informed imputation scheme, to comprehensively account for the uncertainty generated by missing population, management, and herbicide resistance data. Using this framework and a large dataset (178 sites over 3 years) on the densities of a destructive arable weed (Alopecurus myosuroides) we investigate the effects of environment, management, and evolved herbicide resistance, on weed population dynamics.In this study we quantify the marginal effects of a suite of common management practices, including cropping, cultivation, and herbicide pressure, and evolved herbicide resistance, on weed population dynamics.Using this framework, we provide the first empirically backed demonstration that herbicide resistance is a key driver of population dynamics in arable weeds at regional scales. Whilst cultivation type had minimal impact on weed density, crop rotation, and earlier cultivation and drill dates consistently reduced infestation severity.Synthesis and applications: As we demonstrate that high herbicide resistance levels can produce extremely severe weed infestations, monitoring herbicide resistance is a priority for farmers across Western Europe. Furthermore, developing non‐chemical control methods is essential to control current weed populations, and prevent further resistance evolution. We recommend that planning interventions that centre on crop rotation and incorporate spring sewing and cultivation to provide the best reductions in weed densities. More generally, by directly accounting for missing data our framework permits the analysis of management practices with data that would otherwise be severely compromised. [ABSTRACT FROM AUTHOR]

Changing political demands requires the search for alternatives to glyphosate, which has often been used in the stale seedbed method. In three field trials between 2020 and 2023, three electrophysical treatments (XPower System, Zasso®) differing in speed, three mechanical treatments (disc harrow, rotary harrow, cultivator) and three chemical treatments (glyphosate, maleic hydrazide, pelargonic acid + maleic hydrazide) were evaluated concerning the efficacy and economic performance in stale seedbed method in Alopecurus myosuroides control. Process costs for each treatment were calculated. Furthermore, the maximum investment costs for the XPower system were calculated to be on the same level as the other treatments. In all treatments, the density of A. myosuroides in autumn was significantly lower than in the control. In general, the fewest plants and heads were found in the chemical treatments. Despite the lower plant density, the electrophysical method did not show a significant difference in the number of heads compared to the untreated control, especially at higher speeds. Calculated process costs ranged between 40 €/ha (glyphosate) and 430 €/ha (pelargonic acid + maleic hydrazide). To be economically comparable with the other treatments, the investment of the XPower should be at maximum between - 219 000 € (glyphosate) and 300 000 € (pelargonic acid + maleic acid), depending on the driving speed. In a holistic view, electrophysical control, as well as pelargonic acid and maleic hydrazide as glyphosate alternatives in the stale seedbed method, are not suitable. A stale seedbed with mechanical control of A. myosuroides is recommended.

Changing political demands requires the search for alternatives to glyphosate, which has often been used in the stale seedbed method. In three field trials between 2020 and 2023, three electrophysical treatments (XPower System, Zasso®) differing in speed, three mechanical treatments (disc harrow, rotary harrow, cultivator) and three chemical treatments (glyphosate, maleic hydrazide, pelargonic acid + maleic hydrazide) were evaluated concerning the efficacy and economic performance in stale seedbed method in Alopecurus myosuroides control. Process costs for each treatment were calculated. Furthermore, the maximum investment costs for the XPower system were calculated to be on the same level as the other treatments. In all treatments, the density of A. myosuroides in autumn was significantly lower than in the control. In general, the fewest plants and heads were found in the chemical treatments. Despite the lower plant density, the electrophysical method did not show a significant difference in the number of heads compared to the untreated control, especially at higher speeds. Calculated process costs ranged between 40 €/ha (glyphosate) and 430 €/ha (pelargonic acid + maleic hydrazide). To be economically comparable with the other treatments, the investment of the XPower should be at maximum between - 219 000 € (glyphosate) and 300 000 € (pelargonic acid + maleic acid), depending on the driving speed. In a holistic view, electrophysical control, as well as pelargonic acid and maleic hydrazide as glyphosate alternatives in the stale seedbed method, are not suitable. A stale seedbed with mechanical control of A. myosuroides is recommended. [ABSTRACT FROM AUTHOR]

Alopecurus myosuroides (blackgrass) is a problematic weed of Western European winter wheat, and its success is largely due to widespread multiple-herbicide resistance. Previous analysis of F2 seed families derived from two distinct blackgrass populations exhibiting equivalent non-target site resistance (NTSR) phenotypes shows resistance is polygenic and evolves from standing genetic variation. Using a CIDER-seq pipeline, we show that herbicide-resistant (HR) and herbicide-sensitive (HS) F3 plants from these F2 seed families as well as the parent populations they were derived from carry extra-chromosomal circular DNA (eccDNA). We identify the similarities and differences in the coding structures within and between resistant and sensitive populations. Although the numbers and size of detected eccDNAs varied between the populations, comparisons between the HR and HS blackgrass populations identified shared and unique coding content, predicted genes, and functional protein domains. These include genes related to herbicide detoxification such as Cytochrome P450s, ATP-binding cassette transporters, and glutathione transferases including AmGSTF1. eccDNA content was mapped to the A. myosuroides reference genome, revealing genomic regions at the distal end of chromosome 5 and the near center of chromosomes 1 and 7 as regions with a high number of mapped eccDNA gene density. Mapping to 15 known herbicide-resistant QTL regions showed that the eccDNA coding sequences matched twelve, with four QTL matching HS coding sequences; only one region contained HR coding sequences. These findings establish that, like other pernicious weeds, blackgrass has eccDNAs that contain homologs of chromosomal genes, and these may contribute genetic heterogeneity and evolutionary innovation to rapidly adapt to abiotic stresses, including herbicide treatment. [ABSTRACT FROM AUTHOR]

The development of resistance in Alopecurus myosuroides populations to different herbicide active ingredients in Europe exacerbates efforts toward its chemical control. In Europe, cinmethylin provides an additional mode of action for the control of A. myosuroides. The objective of this study was to evaluate three resistance weed management (RWM) strategies, including cinmethylin and other pre‐emergence herbicides, for the control of multiple herbicide–resistant A. myosuroides. The RWM strategies used in this study differed in the extent of preventive cultural practices (tillage, crop rotation, sowing date and stale seedbed). Two field trials were conducted at sites with ACCase‐ and ALS‐resistant A. myosuroides biotypes in Germany between 2017 and 2020. Cinmethylin was included in the herbicide regime for A. myosuroides control. The combination of initial inversion tillage, delayed sowing, crop rotation diversification, and stale seedbed reduced the density of A. myosuroides bup to 90% compared to a strategy with pre‐emergence herbicides used as main components in control. At both sites, the amount of viable A. myosuroides seeds in the soil seed bank was reduced by over 90% after a 3‐year trial period in plots with initial inversion tillage. Molecular analyses revealed that the omission of ACCase and ALS inhibitors did not reduce the proportion of resistant A. myosuroides biotypes. Long‐term control of resistant A. myosuroides must be based on a combination of cultural practices that reduce the soil seed bank and suppress the occurrence of A. myosuroides and the use of still‐effective active ingredients for preventing the renewed entry of seeds into the soil. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

The basic mechanism of soil inversion tillage for control of annual weeds is based on the vertical translocation of weed seeds from the soil surface to deeper soil layers. Buried weed seeds either remain dormant in the soil seedbank and are exposed to biological and chemical decay mechanisms, or they germinate but the seedlings cannot reach the soil surface (fatal germination). However, depending on the seed biology of the respective target species, frequent inversion tillage can lead to a build‐up of the soil seedbank. For soil seedbank depletion based on available knowledge of the biology of Alopecurus myosuroides seeds, soil inversion tillage is suggested to be reduced to every third or fourth year with reduced or even no‐tillage (direct seeding) in between (rotational inversion tillage systems). Including spring crops in the crop rotation could further help dampening the population growth and hence the seed return into the seedbank. This study investigated the effect of rotational inversion tillage in combination with reduced tillage or direct seeding on the soil seedbank and population development of A. myosuroides. In a long‐term field trial, set up in 2012, these tillage strategies were compared with continuous inversion tillage in a 3‐year crop rotation with two consecutive years of winter wheat (Triticum aestivum) followed by spring barley (Hordeum vulgare). The results showed a significant decline in the soil seedbank following the spring crop, irrespective of the tillage system. The continuous inversion tillage system and inversion tillage before spring cropping with reduced tillage (shallow tillage with a disc harrow) before winter wheat both led to accumulation of seeds in the soil seedbank. In contrast, inversion tillage before spring cropping with direct seeding of winter wheat depleted the soil seedbank significantly after only one crop rotation. Although only covering one intensively studied field site, these findings highlight the need for diversified cropping systems and indicate potential avenues for reducing soil tillage while controlling economically important weeds. [ABSTRACT FROM AUTHOR]

Delayed sowing of winter cereals in Western Europe is a preventive method to reduce Alopecurus myosuroides infestations. Two series of on-farm studies including 36 experiments were conducted in South-Western Germany to analyse the combined effects of delayed sowing and pre-emergence herbicide application on A. myosuroides density, weed control efficacy and cereal grain yield. From 2006 until 2009, pendimethalin + flufenacet was applied one week after sowing winter barley and winter wheat. From 2018 until 2020, cinmethylin was used in winter wheat and winter triticale. Densities of A. myosuroides in the untreated early sown control plots amounted up to 1 233 plants/m2. Delayed sowing on average reduced densities by 43%. The mixture of pendimethalin + flufenacet in combination with delayed sowing controlled 87% of the A. myosuroides plants and increased cereal grain yields from 6.4 t/ha in the early sown untreated control to 7.9 t/ha. Cinmethylin in combination with delayed sowing resulted in 91% weed control efficacy and increased grain yields from 5.3 t/ha to 8.8 t/ha. Average grain yields of all delayed sowing treatments were 0.7 t/ha higher than in the early sown treatments. Therefore, delayed sowing combined with pre-emergence herbicide application is a cost-effective strategy of integrated weed management (IWM) in winter cereals reducing dependency on post-emergence herbicide use and mitigating the risk of herbicide resistance development.

Resistance of blackgrass (Alopecurus myosuroides Huds.) and silky bentgrass (Apera spica-venti (L.) P. Beauv.) to ACCase inhibitors is a serious issue in winter cereals throughout Europe, especially as hormesis induced by herbicides has been observed in some populations. According to the literature, growth-stimulating herbicide rates are on the rise. The aim of this study was to assess the responses of A. myosuroides and A. spica-venti, which are potentially resistant to ACCase inhibitors, to fenoxaprop-P-ethyl and pinoxaden applied at rates up to 8 times greater than their registered rates. The reaction of A. myosuroides to fenoxaprop-P-ethyl and pinoxaden resulted in an increase in biomass gain in six and four populations, respectively. In one population of A. myosuroides, this increase was statistically significant (46.4% and 55.3%). All three potentially resistant A. spica-venti populations tested were at least partially stimulated by fenoxaprop-P-ethyl, while pinoxaden only stimulated the APSII population (significant increase of 43.8%). Predictions of the possible impact of herbicides on the reproductive potential of the tested populations allow genotypes to be identified whose reproduction may be stimulated by the herbicides. The results of this study indicate that the tested populations can induce mechanisms that reduce the negative impact of the applied herbicides, with some populations demonstrating the effect of stimulating the accumulation of biomass in the treated plants. [ABSTRACT FROM AUTHOR]

Cinmethylin, a pre-emergent applied active ingredient, inhibits the fatty acid thioesterase and offers a new option in the chemical control of Alopecurus myosuroides, one of the most problematic weeds in arable farming in Europe. It was assumed that with the delayed sowing of winter wheat and winter barley due to more humid and cooler conditions, the efficacy of cinmethylin against A. myosuroides increases. Four field trials were conducted in Southwestern Germany from 2019 to 2022. From mid-September until early November, winter wheat and winter barley were sown in at four dates each year, with intervals of fourteen days. After each sowing, 500 and 250 g cinmethylin ha−1 were applied subsequently to winter wheat and winter barley, respectively. Flufenacet (240 g ha−1) served as a comparison in both crops. A herbicide efficacy of over 90% was achieved for winter wheat sown in mid-October, while it was only 70% for winter wheat sown in mid-September. Similar results were observed for winter barley. On average, cinmethylin achieved a significantly higher efficacy in winter wheat than flufenacet. The presented approach with cinmethylin and delayed sowing date provides a basis for the comprehensive control of A. myosuroides. However, further measures of integrated weed management (crop rotation, situational ploughing, and stale seedbed) need to be applied for 100% control. [ABSTRACT FROM AUTHOR]

Die Bekämpfung von Ackerfuchsschwanz (Alopecurus myosuroides Huds.) stellt vor dem Hintergrund der zunehmenden Resistenzen eine Herausforderung dar. Strategien zur Resistenzvermeidung beinhalten das Alternieren der Wirkstoffe oder ihre Anwendung in Mischungen bzw. in Sequenz. Unabhängig der gewählten Strategie stellt sich immer die Frage welche Resistenzmechanismen durch welche Anwendung positiv, gar nicht oder negativ selektiert werden. Der Blick in dieser Arbeit wird auf die metabolische Resistenz (NTSR) gelegt. Ihre Evolution erfolgt in kleinen quantifizierbaren Schritten und die Ausprägung von Kreuzresistenzen gegen weitere Wirkstoffe bleibt schwer vorhersagbar. Mit den im Getreide zur Bekämpfung von Ackerfuchsschwanz (Alopecurus myosuroides Huds.) eingesetzten Wirkstoffen Pinoxaden (HRAC 1) und Pyroxsulam (HRAC 2) wurde die Evolution von Resistenz bzw. Kreuzresistenz in Gewächshausversuchen für die 1. Generation experimentell simuliert. Dazu wurde eine Anzucht aus der ursprünglichen Feld-Population in drei Teilpopulationen unterteilt. Diese Teilpopulationen wurden mit jeweils 10 % der Feldaufwandmenge der Einzelwirkstoffe Pinoxaden und Pyroxsulam oder der Mischung dieser Wirkstoffe behandelt. Die Überlebenden dieser Behandlung wurden dann getrennt als Teilpopulation weiter vermehrt (F1). Die Empfindlichkeit der drei F1-Populationen und der Elterngeneration (P) gegenüber Pinoxaden, Pyroxsulam und der Mischung wurde in insgesamt 12 Dosis-Wirkungsversuchen verglichen. Die mit Pinoxaden selektierte F1-Population zeigte als einzige Teilpopulation eine signifikante Verschiebung der Unempfindlichkeit gegen Pinoxaden im Vergleich zu der P-Generation mit einem Faktor von 6. Nach Selektion in nur einer Generation konnte eine spezifisch gegen Pinoxaden metabolische Resistenz selektiert werden, die sich mit der Feldaufwandmenge nicht mehr ausreichend bekämpfen ließ.

The herbicide flufenacet, applied in pre-emergence, acts as an inhibitor of the synthesis of very long-chain fatty acids (HRAC group 15) and is an important component in the control of grasses in winter cereals, especially when resistance to other herbicide groups already exists. However, decreases in sensitivity due to increased flufenacet metabolism by glutathione transferase activity have already been described in some black-grass (Alopecurus myosuroides Huds.) populations. So far, little is known about the mechanisms of gene regulation in metabolically resistant weeds. Therefore, we aligned RNA-seq data from two sensitive black-grass populations and two black-grass populations with reduced sensitivity to flufenacet against the recently sequenced black-grass genome. In a differential gene expression analysis, an upregulation of genes involved in metabolic detoxification pathways, such as cytochrome P450 monooxygenases (CYPs), glycosyltransferases (GTs), glutathione transferases (GSTs) and ATP-binding cassette (ABC) transporters was observed. It was found that 7% of the GST genes in the two populations with reduced flufenacet sensitivity were significantly upregulated even without any herbicide application (constitutively) when compared to the two sensitive populations. Three of these genes are located next to each other on the third chromosome and represent a cluster. For each of the upregulated GST genes 3,5 kb of the upstream promoter region were investigated in silico for potential transcription factor binding sites (TFBSs). Some of them share common upstream motifs, such as an ocs element, previously described as enhancer element for GSTs. In addition, other motifs could act as potential binding sites for transcription factors (TFs) that were found upregulated. These belonged to various classes including WRKYs, basic helix-loop-helices (bHLH), basic leucine zippers (bZIP) or MADS-boxes. A better understanding of the regulation of resistanceassociated genes can contribute to improve diagnosis of herbicide resistance and help in predicting the evolution of cross-resistance, as well as contribute to the search for new active ingredients.

Delayed sowing of winter cereals in Western Europe is a preventive method to reduce Alopecurus myosuroides infestations. Two series of on-farm studies including 36 experiments were conducted in South-Western Germany to analyse the combined effects of delayed sowing and pre-emergence herbicide application on A. myosuroides density, weed control efficacy and cereal grain yield. From 2006 until 2009, pendimethalin + flufenacet was applied one week after sowing winter barley and winter wheat. From 2018 until 2020, cinmethylin was used in winter wheat and winter triticale. Densities of A. myosuroides in the untreated early sown control plots amounted up to 1 233 plants/m². Delayed sowing on average reduced densities by 43%. The mixture of pendimethalin + flufenacet in combination with delayed sowing controlled 87% of the A. myosuroides plants and increased cereal grain yields from 6.4 t/ha in the early sown untreated control to 7.9 t/ha. Cinmethylin in combination with delayed sowing resulted in 91% weed control efficacy and increased grain yields from 5.3 t/ha to 8.8 t/ha. Average grain yields of all delayed sowing treatments were 0.7 t/ha higher than in the early sown treatments. Therefore, delayed sowing combined with preemergence herbicide application is a cost-effective strategy of integrated weed management (IWM) in winter cereals reducing dependency on post-emergence herbicide use and mitigating the risk of herbicide resistance development. [ABSTRACT FROM AUTHOR]

Die Auswertung von Kleinparzellen-Versuchen der letzten 20 Jahre zeigt eine Abhängigkeit der Wirksamkeit Metazachlor-haltiger Herbizide gegen Acker-Fuchsschwanz von Anwendungstermin und Aufwandmenge. Die höchsten Wirkungsgrade mit der geringsten Streuung werden im Vorauflauf erzielt. Bei reinen Metazachlor- Produkten liegen diese bei 500 g/ha Metazachlor bei 75 % Wirkung und bei 750 g/ha Metazachlor bei etwas über 80 % Wirkung. Im Nachauflauf ist die Variabilität aufgrund unterschiedlicher Entwicklungsstadien höher und die Wirkungsgrade sind im Durchschnitt um häufig 5-10 % niedriger. Auch Dimethenamid-P-haltige Herbizide ohne Metazachlor (z.B. Tanaris®) weisen eine Nebenwirkung gegen Acker-Fuchsschwanz auf. Diese liegt bei 500 g/ha Dimethenamid-P durchschnittlich bei 60-65 % und fällt im Nachauflauf weniger stark ab, verglichen mit Metazachlor. Die Kombination aus 500 g/ha Dimethenamid-P und 500 g/ha Metazachlor, wie sie in den Produkten Butisan® Gold und Butisan® Kombi vorliegt, erzielt hinsichtlich Wirkungsgrad und Wirkungssicherheit dieselben Ergebnisse wie 750 g/ha Metazachlor solo. Die Rücknahme der Metazachlor-Aufwandmenge von 750 g/ha auf 500 g/ha wird somit durch die Ergänzung mit Dimethenamid-P bei der Acker-Fuchsschwanz-Wirkung vollständig kompensiert. Idealerweise sollte Winterraps in der Fruchtfolge dafür genutzt werden, den Acker-Fuchsschwanz-Besatz durch Verhinderung von Samen-Neubildung zu reduzieren. Die dafür nötigen hohen Wirkungsgrade lassen sich erzielen mit Spritzfolgen bestehend aus Butisan® Gold/Butisan® Kombi gefolgt von Focus® Aktiv-Pack (sofern keine ACCase-Wirkort-Resistenz vorliegt) oder einem Propyzamid-Produkt. Zusätzlich trägt die Reduzierung von Metazachlor zum Wirkstofferhalt bei. Eine Senkung der Aufwandmenge auf maximal 500 g/ha Metazachlor reduziert automatisch die Menge nicht relevanter Metaboliten und trägt dazu bei, das „Risiko“ möglicher Versickerungen ins Grundwasser zu minimieren. Die Leistung der Kombi- Produkte ist bei der reduzierten Metazachlor-Menge gegenüber reinen Metazachlor-haltigen Produkten mit höherer Metazachlor-Menge gegen Acker-Fuchsschwanz gleichwertig, bei den meisten anderen Unkräutern überlegen.

Abstract Globally, herbicide resistance in weeds poses a threat to food security. Resistance evolves rapidly through the co‐option of a suite of physiological mechanisms that evolved to allow plants to survive environmental stress. Consequently, we hypothesize that stress tolerance and herbicide resistance are functionally linked. We address two questions: (i) does exposure to stress in a parental generation promote the evolution of resistance in the offspring? (ii) Is such evolution mediated through non‐genetic mechanisms? We exposed individuals of a grass weed to drought, and tested whether this resulted in herbicide resistance in the first generation. In terms of both survival and dry mass, we find enhanced resistance to herbicide in the offspring of parents that had been exposed to drought. Our results suggest that exposure of weeds to drought can confer herbicide resistance in subsequent generations, and that the mechanism conferring heritability of herbicide resistance is non‐genetic.

Seed predation can reduce the abundance and spread of unwanted vegetation in agricultural and other semi‐natural ecosystems. However, knowledge of how variations in seed predation rates affect plant species population dynamics is needed for decision making and knowledge‐based ecosystem management.We developed a stage‐classified stochastic matrix population model for Alopecurus myosuroides Huds. (blackgrass), an annual plant species thriving as a weed in temperate agroecosystems of Western and Northern Europe. The model was parameterised using empirical demographic data from long‐term experiments in Swedish winter wheat fields, including information on post‐dispersal seed losses by vertebrate and invertebrate seed predators.For agroecosystems with highly effective weed control measures (e.g. chemical and mechanical weed control), model simulations showed that seed losses via seed predation need to reach at least 78% at peak seed shedding to suppress population growth of A. myosuroides.The field experiment showed that vertebrates were most important for seed predation in July, at peak seed shedding. In August, after crop harvest, invertebrates were responsible for almost all seed predation. The model indicated that weed seed predation was much more important for weed regulation when it occurred before crop harvest in July. Vertebrates most strongly reduced population growth of A. myosuroides, although both vertebrates and invertebrates were needed to prevent it entirely.Synthesis and applications. We showed that weed seed predation by vertebrate and invertebrate seed predators is key for reducing the population growth of winter annual weeds like A. myosuroides in intensively managed agroecosystems. Therefore, protection of weed seed predators is essential for making management of unwanted vegetation less dependent on chemical and mechanical measures. [ABSTRACT FROM AUTHOR]

Copyright of Julius-Kühn-Archiv is the property of Julius Kuehn Institut and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Globally, herbicide resistance in weeds poses a threat to food security. Resistance evolves rapidly through the co‐option of a suite of physiological mechanisms that evolved to allow plants to survive environmental stress. Consequently, we hypothesize that stress tolerance and herbicide resistance are functionally linked. We address two questions: (i) does exposure to stress in a parental generation promote the evolution of resistance in the offspring? (ii) Is such evolution mediated through non‐genetic mechanisms? We exposed individuals of a grass weed to drought, and tested whether this resulted in herbicide resistance in the first generation. In terms of both survival and dry mass, we find enhanced resistance to herbicide in the offspring of parents that had been exposed to drought. Our results suggest that exposure of weeds to drought can confer herbicide resistance in subsequent generations, and that the mechanism conferring heritability of herbicide resistance is non‐genetic. [ABSTRACT FROM AUTHOR]

Copyright of Progress in Plant Protection is the property of Institute of Plant Protection and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Turkish Journal of Weed Science is the property of Gaziosmanpasa Universitesi Matbaasi, Department of Plant Protection, Faculty of Agriculture and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Resistance of blackgrass (Alopecurus myosuroides Huds.) and silky bentgrass (Apera spica-venti (L.) P. Beauv.) to ACCase inhibitors is a serious issue in winter cereals throughout Europe, especially as hormesis induced by herbicides has been observed in some populations. According to the literature, growth-stimulating herbicide rates are on the rise. The aim of this study was to assess the responses of A. myosuroides and A. spica-venti, which are potentially resistant to ACCase inhibitors, to fenoxaprop-P-ethyl and pinoxaden applied at rates up to 8 times greater than their registered rates. The reaction of A. myosuroides to fenoxaprop-P-ethyl and pinoxaden resulted in an increase in biomass gain in six and four populations, respectively. In one population of A. myosuroides, this increase was statistically significant (46.4% and 55.3%). All three potentially resistant A. spica-venti populations tested were at least partially stimulated by fenoxaprop-P-ethyl, while pinoxaden only stimulated the APSII population (significant increase of 43.8%). Predictions of the possible impact of herbicides on the reproductive potential of the tested populations allow genotypes to be identified whose reproduction may be stimulated by the herbicides. The results of this study indicate that the tested populations can induce mechanisms that reduce the negative impact of the applied herbicides, with some populations demonstrating the effect of stimulating the accumulation of biomass in the treated plants.

The growth of resistance to multiple herbicides in grass weeds is a major threat to global cereal production and in the UK, is epitomized by the loss of control of blackgrass (Alopecurus myosuroides), causing losses in winter wheat production equating to 5% of national consumption. With an urgent need to develop new black-grass management tools, we have developed a lateral flow assay (LFA) that can predict resistance to multiple herbicides within 10 min. • Rapid diagnostics of herbicide resistance. • Lateral flow assay. • Applications in wild grasses. [ABSTRACT FROM AUTHOR]

BACKGROUND: Alopecurus myosuroides (blackgrass) is a major weed in Europe with known resistance to multiple herbicide modes of action. In the UK, there is evidence that blackgrass has undergone a range expansion. In this paper, genotyping‐by‐sequencing and population‐level herbicide resistance phenotypes are used to explore spatial patterns of selectively neutral genetic variation and resistance. We also perform a preliminary genome‐wide association study (GWAS) and genomic prediction analysis to evaluate the potential of these approaches for investigating nontarget site herbicide resistance. RESULTS: Blackgrass was collected from 47 fields across the British Isles and up to eight plants per field population (n = 369) were genotyped by Restriction site‐associated DNA (RAD)‐sequencing. A total of 20 426 polymorphic loci were identified and used for population genetic analyses. Phenotypic assays revealed significant variation in herbicide resistance between populations. Population structure was weak (FST = 0.024–0.048), but spatial patterns were consistent with an ongoing westward and northward range expansion. We detected strong and consistent Wahlund effects (FIS = 0.30). There were no spatial patterns of herbicide resistance or evidence for confounding with population structure. Using a combination of population‐level GWAS and genomic prediction we found that the top 20, 200, and 2000 GWAS loci had higher predictive abilities for fenoxaprop resistance compared to all markers. CONCLUSION: There is likely extensive human‐mediated gene flow between field populations of the weed blackgrass at a national scale. The lack of confounding of adaptive and neutral genetic variation can enable future, more extensive GWAS analyses to identify the genetic architecture of evolved herbicide resistance. © 2020 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Effective control of Alopecurus myosuroides Huds. (blackgrass) solely with a chemical treatment is not guaranteed anymore because populations exhibit resistance to almost all herbicide modes of action. Integrated weed management (IWM) against blackgrass is necessary to maintain high weed control efficacies in winter cereals. Four field experiments were conducted in Southwest Germany from 2018 to 2020 to control A. myosuroides with a combination of cultural and chemical methods. Stubble treatments, including flat, deep and inversion soil tillage; false seedbed preparation and glyphosate use, were combined with the application of the new pre-emergence herbicide cinmethylin in two rates in winter wheat. Average densities of A. myosuroides in the untreated control plots were up to 505 plants m−2. The combination of different stubble management strategies and the pre-emergence herbicide cinmethylin controlled 86–97% of A. myosuroides plants at the low rate and 95–100% at the high rate until 120 days after sowing. The different stubble tillage practices varied in their efficacy between trials and years. Most effective and consistent were pre-sowing glyphosate application on the stubble and stale seedbed preparation with a disc harrow. Stubble treatments increased winter wheat density in the first year but had no effect on crop density in the second year. Pre-emergence application of cinmethylin did not reduce winter wheat densities. Multiple tactics of weed control, including stubble treatments and pre-emergence application of cinmethylin, provided higher and more consistent control of A. myosuroides. Integration of cultural weed management could prevent the herbicide resistance development.

The evolution of herbicide resistance is an important topic in plant protection and agricultural practice. Safeners are commonly used in herbicides to protect crops against herbicidal damage. Although no effect on the weed control is expected, it has been theorized that the rate of evolution of non-target site resistance (NTSR) in weeds in cereals may be enhanced by use of herbicide products containing safeners. One of the most important safeners in cereals is mefenpyr-diethyl. Therefore, the possible influence of mefenpyr on herbicide resistance was studied in cooperative trials between Bayer CropScience (BCS, F-Höchst) and FH Bingen. The trials tested in parallel different herbicide resistant black-grass (Alopecurus myosuroides (Huds.)) biotypes under greenhouse conditions. The biotypes where chosen due to known NTSR against Atlantis WG® (4 highly resistant and 5 moderately resistant) as well as two susceptible biotypes. The populations were treated with the following three herbicide/safener regimes in six concentrations adjusted according to the anticipated biotype resistance levels. (1) mesosulfuron + iodosulfuron + without safener formulation, (2) mesosulfuron + iodosulfuron + constant mefenpyr concentration (45g/ha), (3) mesosulfuron + iodosulfuron + varying mefenpyr concentrations (ratio 5:1:15). The treatments were applied in post-emergence based on mesosulfuron to iodosulfuron ratios in Atlantis WG® (5:1). The trials were assessed visually (% effect) and by fresh weight. Dose-response curves were performed and ED50 values for each treatment and biotype were calculated. Results showed a varying effect of safeners which was in the most cases negligible. Depending on the biotypes mostly no impact on the safener was found for herbicide resistance. In conclusion, the trials from Bingen and F-Höchst gave evidence, that there is no significant and consistent influence of the safener mefenpyr on evolution of NTSR black-grass.

The repetitive use of herbicides as major tool to control troublesome weeds in agriculture caused an increase in resistant weeds lately, especially when Integrated Weed Management principles were ignored. In a case study approach we sampled blackgrass (Alopecurus myosuroides Huds.) in three distinctive locations for at least 3 years. Based on field infestation level, greenhouse biotests and laboratory analyses we grouped 23 fields as resistant (R), 28 fields as less sensitive (I) and 39 fields as sensitive (S) with regard to their ALS resistance status. Field history information was collected for 90 fields. Variables regarding the frequency of 1) summer crops, 2) winter cereals, 3) ploughing, 4) herbicide use, and 5) early versus late seeding were calculated. Fields with a higher frequency of summer crops, ploughing and later sowing dates in the crop rotation were less frequently grouped into R and I. No relationship was found between the number of modes of action used and the resistance status. Intensity of ALS-inhibitor use and use of grass herbicides played a role to distinguish resistant from sensitive fields. Our results suggest that cultural measures to bring the blackgrass population size to lower levels are more important than the selection by the herbicide.

Copyright of Julius-Kühn-Archiv is the property of Julius Kuehn Institut and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Julius-Kühn-Archiv is the property of Julius Kuehn Institut and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The efficacy of different ALS-inhibiting herbicides for the control of brome species (Bromus spp.) was tested in three field trials in the year 2010 – 2012 in the region of North-West-Bavaria Franken. As a result of the trials the standard herbicide Attribut (Propoxycarbazone) was confirmed for the control of brome. In case of infestation with brome and black grass the herbicide Broadway (Pyroxsulam) offers a certain control of both problematic grass weeds. This illustrates the high dependency of sufficient brome control in winter cereals on the effectiveness of specific ALS-Inhibitor herbicides. Because of the high risk of herbicide resistance to ACCaseand ALS-inhibiting herbicides in brome, integrated weed management is essential for the sustainable control of brome in winter cereals, respectively winter wheat.

The increasing number of herbicide tolerant weed populations is illustrating the increasing demand for reliable methods for an accelerated detection of herbicide tolerance compared to greenhouse studies. Several methods for resistance quick detection have been published in previous years. One of the recent methods is the Chlorophyll Fluorescence Imaging Method (CFI). For this method changes in photosynthetic activity of the target organisms, caused by herbicides, are determined. General assumption of this method in terms of herbicide resistance detection is that each herbicidal compound, independent of the mode of action, will cause changes within the photosynthetic apparatus of the target organisms. This effect already could be confirmed for several modes of action (PSII, ALS, ACCase, EPSPS, synth. Auxins). Aim of this study is to validate this novel method on the basis of greenhouse experiments and single nucleotide polymorphisms (SNP) analysis. The resistance profiles of 10 black-grass populations (Alopecurus myosuroides Huds.) have been determined in greenhouse herbicide efficacy trials and constitutive SNP analyses of the survivors. With the CFI-method it was possible to detect the resistance profile as well as the resistance frequency within the populations. The results from the greenhouse experiments could be reproduced with conformity of 94%. This result is valid for the tested herbicides mesosulfuron, pyroxsulam as well as clodinafop and pinoxaden.

Black-grass (Alopecurus myosuroides, Huds.) is the most important herbicide-resistant weed in Europe. In Germany it is not only a problem in the maritime influenced areas like Schleswig-Holstein and Lower Saxony anymore, as well in other regions black-grass develops to the most important weed in winter wheat and oilseed rape. There are multifaceted reasons for that, one reason are close winter crop rotations and early sowing dates which are economically very attractive for the farmers, another one are herbicide resistances. Black-grass germinates in autumn and in spring, but the main germination period is from late August to early October. If winter wheat is sown early in autumn, the main germination is in parallel to the wheat. Then the weeds can only be managed by culture specific herbicides. The pressure on the herbicides is therefore increasing. Herbicide resistances can be the result. As long as very effective herbicides are available, so that farmers are not dependent on weed biology and plant production weed management measures such as sowing date. Late sowing dates can reduce the black-grass populations, but this option is not attractive to many farmers in Schleswig-Holstein. In mind of the farmers the risk of delayed sowing dates in autumn is too high, because increased rainfall such as can make it difficult to marsh soils sowing, or make impossible. Objective of this trial was the germination of Black-grass to show to two sowing dates. The results of the field trial show, that black-grass populations can be reduced if winter wheat is sown later in autumn.

A transcriptomics approach was chosen in order to determine candidate genes for metabolic herbicide resistance in a quantitative comparison of expressed genes in sensitive wild type and resistant blackgrass (Alopecurus myosuroides = ALOMY) plants. Firstly a reference transcriptome for blackgrass was established by means of a paired-end RNA-Seq protocol prepared from control and herbicide treated plants from a metabolic resistant biotype. Secondly gene expression was measured in different metabolic resistant ALOMY biotypes and a representative selection of sensitive wild type plants using a 3´-specific RNA sequencing strategy and related to the reference transcriptome. By comparing expression levels for individual genes in wild type and resistant blackgrass biotypes candidate genes from the group of glutathione transferases were identified. Further analyses will be necessary in order to verify a close correlation with the metabolic resistance.

The repetitive use of herbicides of a given mode of action as primary tools to control weeds in simplified cropping systems has led to the development of resistant populations. This study reports preliminary results of the infestation level and the herbicide resistance structure of blackgrass (Alopecurus myosuroides Huds.) in circa 40 neighboring fields in each of three locations in Southern Germany during 2010-2012. In each location one field with confirmed field resistance served as a starting point to survey the surrounding fields. Field infestation was assessed at the end of the season where seeds were harvested. Based on greenhouse biotests nearly all tested fields showed resistance to ACCase, but the pattern of ACCase mutations and metabolic resistance to fenoxaprop-ethyl showed differences according to space and time. High resistance to ALS was found in several fields in two locations where ALS-resistance was previously confirmed in a single field only leading to severe crop failure. Interestingly, either Pro197 or Trp574 seemed to dominate in these two locations, while almost no ALS target-site mutations were found in the third location. Target-site mutations appear to be the major mechanism for these early cases of ALS-resistance. A few fields also showed non-target site resistant plants to mesosulfuron-methyl. This unique data set provides new insights into the structure and development of 1) an established resistance (ACCase-inhibitors) and 2) a developing resistance (ALS-inhibitors). Multivariate analysis including greenhouse biotests data and target-site analyses corresponding to mutations conferring resistance showed that even spatially closely related fields develop different herbicide resistance patterns. This suggests that weed control measures have a major impact within each field and that resistance can evolve independently. In the current situation black-grass infestations can still be controlled in most of the fields. Integrated Weed Management tools can contribute to keep the selection pressure low and slow down resistance development.

Neighboring fields in three local areas of southern Germany have been investigated for the infestation level and herbicide resistance structure of black-grass (Alopecurus myosuroides Huds.). One field within a local area, each with confirmed resistance, served as starting point to survey the surrounding fields. Eighty percent of the fields had very few black-grass ears prior to harvest, with mainly ears from single plants spread over the field. Infestation in the other fields was in large patches or widespread, yet in most situations it did not significantly impact on yield level. Resistance to ACCase-inhibiting herbicides was found on all tested fields in each region. Plants with a target-site mutation to ACCase inhibitors were found in all samples; in addition, most plants also exhibited non-target-site resistance. All five mutations conferring ACCase resistance were found. The diversity of the mutations between areas suggests that resistance evolved independently in most fields. At two locations, each one with confirmed ALS resistance, additional fields with reduced ALS efficacy were detected. At one location only the mutation P197T was found, at the second the W574L mutation was also found. Target-site resistance appears to be the major mechanism for these early cases of ALS inhibitor resistance. Understanding the resistance development in individual fields and the spatial dynamics requires investigation over several years. The example of ACCase resistance to black-grass demonstrates how a specific mode of action can be rendered ineffective over a whole region. It provides a possible model for ALS-inhibiting herbicides. In the current situation, farmers are able to manage the black-grass infestation quite well. Resistance in a field seems to develop first in patches with high population densities. Resistance management should therefore focus on the management of the seed bank of each field, using all measures to keep the population pressure low.

Herbicide resistance in Alopecurus myosuroides causes severe problems in Western European cropping systems. Costs of herbicide resistance were investigated in this study by analysing variable production costs and sales revenues. Three farms were selected for this study, with winter wheat as the dominating crop in all farms. Resistance in A. myosuroides populations was verified at all locations. Four farming approaches were simulated over a period of 20 years: (i) continuing the actual cropping system without increase of resistance, (ii) continuing the actual cropping system with increase of resistance, (iii) changing cropping practice to overcome resistance and (iv) changing cropping practice to prevent resistance. Contribution margins representing the proportion of sales revenue that is not consumed by variable costs were calculated for all approaches. Comparative static simulations showed that average contribution margins in a cropping system with more than 60% winter cereals and reduced tillage practice dropped from 807 € ha−1 a−1 without herbicide resistance to 307 € ha−1 a−1 with herbicide resistance. Alopecurus myosuroides population densities increased to more than 1000 plants m−2. Diverse crop rotations, including spring crops, clover-grass leys and intensive tillage, suppressed A. myosuroides populations, and average contribution margin was 630 € ha−1 a−1. Preventive methods with rotations of winter cereals and spring crops with less clover-grass leys resulted in an average contribution margin of 691 € ha−1 a−1. In conclusion, rotations of winter cereals and spring crops combined with inversion tillage and herbicides provide stable yields and can prevent weed population increase. [ABSTRACT FROM AUTHOR]

Wheat shows selectivity to pyroxsulam, a new broad-spectrum herbicide with high activity on blackgrass. Studies were performed to establish whether uptake, translocation or metabolism were responsible for the differential activity in wheat compared with blackgrass. In addition, the effect of the safener cloquintocet-mexyl on metabolism was evaluated in wheat and blackgrass shoots. Root uptake of pyroxsulam in blackgrass was significantly higher than in wheat, suggesting a possible activity enhancement in blackgrass owing to root uptake. Translocation to foliage from root uptake as well as translocation out of treated foliage following foliar applications was low in wheat compared with blackgrass, likely owing to the rapid metabolism of pyroxsulam in wheat. Wheat metabolized pyroxsulam significantly faster than blackgrass to the less active O-dealkylation product. Wheat shoots metabolized pyroxsulam faster when the safener cloquintocet-mexyl was present, but cloquintocet-mexyl did not increase the rate of metabolism in blackgrass. The selectivity of pyroxsulam to wheat relative to blackgrass was connected primarily with differences in the rate of metabolism and generation of an inactive metabolite. Metabolism in wheat restricted subsequent movement of radioactivity out of the treated leaf. The rapid metabolism in wheat was increased by the addition of cloquintocet-mexyl. Copyright © 2010 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Makowski D, Chauvel B & Munier-Jolain N (2010). Improving a weed population model using a sequential Monte Carlo method. Weed Research 50, 373–382. Field measurements and weed population model predictions have been proposed as the basis for recommendations on the need for chemical or mechanical treatment, but both approaches have some limitations. This study shows how a Sequential Monte Carlo (SMC) method can be used to combine weed count measurements and model predictions, to derive a better estimate of weed population characteristics. SMC was applied to a dynamic model simulating weed densities, seed production and seedbank densities for Alopecurus myosuroides (blackgrass). The benefit resulting from SMC was quantified for several types of weed count data, using experiments carried out in seven plots during 6 years. Compared with the initial model predictions, SMC reduced the root mean squared error (RMSE) by 33.5–81.5%. Compared with the weed densities derived from the weed counts alone, SMC reduced the RMSE by 1.2–10%. SMC should be preferred to the single use of model or of weed count data, because it can improve weed density predictions and because the probability distributions computed by SMC can be used to analyse the uncertainty about the state of the system. [ABSTRACT FROM AUTHOR]

Variation in seed dormancy and light sensitivity was studied in Alopecurus myosuroides and Apera spica-venti. Seeds were collected from different populations, at different dates and from plants emerging in autumn or spring, and used in four experiments. In the first experiment, initial dormancy was investigated in light and darkness. In Expt 2, buried seeds were exhumed on 16 occasions, from September 1997 to March 2000, and germinated in light, in darkness and after a 5-s light exposure. In Expt 3, emergence was recorded for seeds sown in pots outdoors. In Expt 4, stratified seeds of A. myosuroides only were exposed to photon irradiance ranging from 0.1 to 25 600 μmol m−2. Variation was high among seed collections, but both species showed winter annual dormancy patterns. Apera spica-venti germinated to high percentages in autumn but negligibly in spring. Alopecurus myosuroides germinated less in spring when tested in darkness and after a short light exposure and emerged poorly in spring, which reflected photo-desensitisation during cold stratification. We conclude that the peak of emergence in A. myosuroides, and to some extent in A. spica-venti, is largely regulated by exposure to light interacting with low-level dormancy. This offers valuable information regarding optimal timing of weed control measures. [ABSTRACT FROM AUTHOR]

Two grass weeds, Alopecurus myosuroides and Bromus sterilis (syn. Anisantha sterilis ), with restricted geographical distribution in the most southern part of Sweden, have caused recent concern among farmers. We evaluated their potential northward spread in Sweden by growing them, and the geographically widespread Apera spica-venti for comparison, at three sites in southern Sweden over two years using four or five planting dates per year. Results suggest that B. sterilis might become a pest also further north in Sweden, while A. myosuroides seems unlikely to spread northward. [ABSTRACT FROM AUTHOR]

A blackgrass population has developed resistance to fenoxaprop-P-ethyl following field selection with the herbicide for 6 consecutive years. Within this population, 95% of the individuals are also resistant to flupyrsulfuron. Both the inheritance(s) and the mechanism(s) of resistances were investigated by making crosses between the resistant and a susceptible biotype. The inheritance was followed through the F1 and F2 generations either by spraying the herbicide on seedlings at the three-leaf stage or using a seedling bioassay, based on coleoptile length. No maternal effects were evident in the fenoxaprop-P-ethyl responses of the F1 plants, suggesting that the inheritance was nuclear. Some F1 families treated with fenoxaprop-P-ethyl segregated in a 3:1 (resistant:susceptible) ratio, indicating that the resistance was conferred by two dominant and independent nuclear genes. This was confirmed by the 15:1 (R:S) ratio observed in the F2 generation treated with fenoxaprop- P-ethyl. The use of selective inhibitors of herbicide de-toxifying enzymes (aminobenzotriazole, pyperonylbutoxide, malathion and tridiphane) with the F2 plants suggested that each of the two genes may govern two different mechanisms of fenoxaprop-P-ethyl resistance: the ACCase mutation previously postulated and an enhanced herbicide metabolism, mediated by cytochrome P 450 mono-oxygenases (P 450) susceptible to malathion. The P 450 activity may also confer resistance to flupyrsulfuron. This study clearly indicates that two distinct mechanisms of resistance may co-exist in the same plant. [ABSTRACT FROM AUTHOR]

Effective control of Alopecurus myosuroides Huds. (blackgrass) solely with a chemical treatment is not guaranteed anymore because populations exhibit resistance to almost all herbicide modes of action. Integrated weed management (IWM) against blackgrass is necessary to maintain high weed control efficacies in winter cereals. Four field experiments were conducted in Southwest Germany from 2018 to 2020 to control A. myosuroides with a combination of cultural and chemical methods. Stubble treatments, including flat, deep and inversion soil tillage; false seedbed preparation and glyphosate use, were combined with the application of the new pre-emergence herbicide cinmethylin in two rates in winter wheat. Average densities of A. myosuroides in the untreated control plots were up to 505 plants m−2. The combination of different stubble management strategies and the pre-emergence herbicide cinmethylin controlled 86–97% of A. myosuroides plants at the low rate and 95–100% at the high rate until 120 days after sowing. The different stubble tillage practices varied in their efficacy between trials and years. Most effective and consistent were pre-sowing glyphosate application on the stubble and stale seedbed preparation with a disc harrow. Stubble treatments increased winter wheat density in the first year but had no effect on crop density in the second year. Pre-emergence application of cinmethylin did not reduce winter wheat densities. Multiple tactics of weed control, including stubble treatments and pre-emergence application of cinmethylin, provided higher and more consistent control of A. myosuroides. Integration of cultural weed management could prevent the herbicide resistance development. [ABSTRACT FROM AUTHOR]