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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]

This article explores approaches to managing pests that are being developed in response to the faltering effectiveness of antibiotic regimes of chemical control. It focuses on black-grass (Alopecurus myosuroides), an endemic plant in European agriculture that has emerged as a serious yield-robber with increasing levels of herbicidal resistance. Following farmers and agronomists who have developed "integrated" approaches to black-grass management, the article identifies approaches to biosecurity that do not target unwanted life so much as they modulate ecological systems in their entirety. Pathogenesis, in this relational understanding, follows not from breaches of dangerous life into healthy space, but from ecological intra-actions that enable the proliferation of some life to compromise the multispecies livability of the body in question. The article contributes to the literature by detailing how this configurational approach works in the world. It traces the polymorphic spatial imaginaries required to map pests well; the process of knowledge intensification needed to reveal which configurations can resist pathogenesis; and the probiotic biopolitical interventions used to safeguard farmland productivity. The article uses black-grass to present a temporal metanarrative of intensive farming causing ecological blowback, leading to the development of approaches to pest management predicated on a pragmatic tolerance toward unwanted life. [ABSTRACT FROM AUTHOR]

In 35 years of routine screening for herbicide resistance, a total of 3758 seed sample/herbicide combinations were assayed. Resistance testing was done in either pots in glasshouses (chlortoluron, fenoxaprop and mesosulfuron‐methyl + iodosulfuron‐methyl sodium) or Petri‐dishes in incubators (sethoxydim, cycloxydim and pendimethalin). With all herbicides, the relationship between herbicide efficacy and year of sampling was linear, with the slope representing the annual loss of efficacy. This was higher for the ALS inhibitors mesosulfuron + iodosulfuron (3.73% year−1) and ACCase inhibitors sethoxydim/cycloxydim (1.92% year−1) and fenoxaprop (1.36% year−1) than for the substituted urea chlorotoluron (0.69% year−1) and the dinitroaniline pendimethalin (1.10% year−1). These results are consistent with other studies on the relative resistance risk associated with these different modes of action. There was also a surprisingly good correlation between results for random and non‐random resistance testing, which has also been found in studies with other weed species in Canada and Australia. This indicates that routine testing of submitted samples can replace, at least partly, the need for random surveys which tend to be both labour intensive and expensive. These results, compiled over 35 years, show the value of routine resistance screening, not only for detecting resistance at the individual field level ('micro' scale), but also the distribution, evolution and impact of resistance country‐wide ('macro' scale). However, it is important that standardised testing methods, including appropriate reference populations, are used by different testing centres to ensure consistent results. [ABSTRACT FROM AUTHOR]

Summary: Rapid adaptation of weeds to herbicide applications in agriculture through resistance development is a widespread phenomenon. In particular, the grass Alopecurus myosuroides is an extremely problematic weed in cereal crops with the potential to manifest resistance in only a few generations. Target‐site resistances (TSRs), with their strong phenotypic response, play an important role in this rapid adaptive response. Recently, using PacBio's long‐read amplicon sequencing technology in hundreds of individuals, we were able to decipher the genomic context in which TSR mutations occur. However, sequencing individual amplicons are costly and time‐consuming, thus impractical to implement for other resistance loci or applications. Alternatively, pool‐based approaches overcome these limitations and provide reliable allele frequencies, although at the expense of not preserving haplotype information. In this proof‐of‐concept study, we sequenced with PacBio High Fidelity (HiFi) reads long‐range amplicons (13.2 kb), encompassing the entire ACCase gene in pools of over 100 individuals, and resolved them into haplotypes using the clustering algorithm PacBio amplicon analysis (pbaa), a new application for pools in plants and other organisms. From these amplicon pools, we were able to recover most haplotypes from previously sequenced individuals of the same population. In addition, we analysed new pools from a Germany‐wide collection of A. myosuroides populations and found that TSR mutations originating from soft sweeps of independent origin were common. Forward‐in‐time simulations indicate that TSR haplotypes will persist for decades even at relatively low frequencies and without selection, highlighting the importance of accurate measurement of TSR haplotype prevalence for weed management. [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]

Die zunehmende Ausbreitung von Herbizidresistenzen auf ackerbaulich genutzten Flächen stellt Landwirte vor akute Probleme bei der Unkrautbekämpfung. Aufgrund der durch die Resistenzentwicklung immer kleiner werdenden Palette an verfügbaren Wirkstoffen mit ausreichendem Wirkungsgrad ist es notwendig, alternative Bekämpfungsmethoden zu entwickeln und im Rahmen des integrierten Pflanzenschutzes anzuwenden. Der innovative Ansatz des Projektes „LURUU – Lasereinsatz zur Unkrautregulierung bei resistenten Ungräsern und Unkräutern“ basiert auf der thermischen Bekämpfung von resistenten Ungräsern mittels mobiler Lasertechnik. Der laserbasierte Ansatz ermöglicht die gezielte Behandlung von Einzelpflanzen, wodurch Auswirkungen auf die Umwelt und die Kulturpflanzen weitestgehend ausgeschlossen werden können. Somit bietet der Einsatz von Lasertechnik eine nachhaltige und zukunftsorientierte Alternative, um den Einsatz von chemischen Pflanzenschutzmitteln zu reduzieren und so der Resistenzentwicklung entgegenwirken zu können. Ziel des Projektes ist es, die Unkrautbekämpfung mittels Lasertechnik auf ihre Praxistauglichkeit zu untersuchen. Dazu wird ein Laserbehandlungsgerät entwickelt, das in der Lage ist, Ackerfuchsschwanz (Alopecurus myosuroides) und Windhalm (Apera spica-venti) zuverlässig zu erkennen und mittels einer gezielten Laserapplikation effektiv und nachhaltig zu bekämpfen. Für die sichere Erkennung von Ungräsern und Kulturpflanze kommt eine Bilderkennungssoftware zum Einsatz, welche innerhalb des Projektes mit einer Vielzahl von selbsterstellten Fotoaufnahmen trainiert wird. Um die Praxistauglichkeit beurteilen zu können, soll die Laserbehandlung im Rahmen von Feldversuchen mit dem Einsatz von gängigen Herbiziden verglichen und anhand der gewonnenen Daten aus ackerbaulicher, technischer und wirtschaftlicher Perspektive bewertet werden.

ALS-resistant weeds are of major importance in many European agriculture systems. Resistant biotypes showed up in more weed species, more regions and in more crops. Therefore, every method or tool to control weeds, that potentially increases the selection pressure on herbicides and weeds must be handled with care. On the other hand new tools like herbicide tolerant varieties offer new possibilities for weed control. Particularly in sugarbeet, chemical weed control is still a compromise between efficacy and crop selectivity today. ALS-tolerant varieties offer the opportunity to improve crop safety and efficacy. To investigate the influence of these sugar beet varieties on the dynamic of ALS-resistant weed populations in a three-year crop rotation, a six-year field trial was conducted on two experimental sites. Four different weed control strategies were tested, which exhibit different levels of selection pressure to ALS inhibitors. The field trial showed that continuous use of ALS herbicides quickly increased the density of resistant weed populations leading to a large yield reduction. However, this process was much slower, when the frequency of ALS inhibitor use was reduced. Yet, it was not stopped completely. Even the use of alternative modes action was only partly able to slow down the resistance evolution. While weeds resistant to ALS herbicides only could be well controlled, multiple resistant weeds were able to build up a new resistance mechanism (ACCase inhibitor resistance). Here this was the case for Alopecurus myosuroides. As a consequence, use of alternative MoAs failed to control A. myosuroides. Due to these complex interactions sustainable use of herbicide tolerant varieties is not easy in the long run. Advantages might be long lasting when site-specific resistant weed status is adequately addressed.

Climate change is driving the need to investigate responses to water limitation of morphological traits involved in competition for light, the main resource for which crops and weeds compete in conventional temperature and tropical cropping systems, to better understand field crop–weed dynamics. Our objective was to develop an innovative approach to quantify weed species responses to water limitation, using three species. This approach combined (1) key morphological traits involved in competition for light (taken from a mechanistic crop–weed model) as criteria to analyse responses to water limitation and (2) a pot/greenhouse platform allowing automated precision‐watering and daily quantification of soil water availability in each pot. For all species and growth stages, increased plant height per unit of aboveground biomass and production of smaller/thicker leaves were the most noteable responses. Plants with a strong increase in plant height per unit of aboveground biomass in response to water limitation maintained high levels of specific leaf area, even at low soil water availability. Increases in biomass allocation to roots (vs. aboveground parts) and leaves (vs. stems and reproductive organs) were also observed, but not for all species and growth stages. Overall, these effects of water limitation on morphological traits indicate strong interactions between competition for light and water. [ABSTRACT FROM AUTHOR]

Black grass (Alopecurus myosuroides Huds.) is a highly competitive weed in winter wheat fields of China. Due to repeated use of acetolactate synthase (ALS) inhibitors, many A. myosuroides populations have evolved resistance to pyroxsulam in some wheat fields. Research was conducted to determine the molecular basis of herbicide resistance in the AH93 A. myosuroides population. Whole-plant dose–response assay confirmed that the AH93 population was resistant to pyroxsulam with a resistance index of 4.2. Cross- and multiple-resistance assays indicated that the AH93 population was cross-resistant to mesosulfuron-methyl and multiple-resistant to pinoxaden. Sequencing of the ALS and ACCase gene revealed that there was no target-site mutation in ALS, but Trp-2027-Cys and Cys-2088-Arg amino acid mutations in ACCase in the AH93 population. A malathion pretreatment study indicated that the AH93 population might have cytochrome P450–mediated herbicide metabolic resistance. This is the first report of pyroxsulam resistance in a multiple-resistant A. myosuroides population in China, and the Cys-2088-Arg mutation is the first reported case of an ACCase mutant conferring herbicide resistance in A. myosuroides. [ABSTRACT FROM AUTHOR]

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 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.)

Due to ecotoxicological and environmental reasons, chemical treatments for weed control are under discussion. To help farmers in coping with challenges imposed by restricted herbicide availability, projects on using modified crop rotations for reducing weed pressure, digital approaches for better decision support, and a better integration of non-chemical weeding were initiated. First monitoring programs in winter oilseed rape in Luxembourg offered a preliminary overview about mainly widespread weed species like Stellaria media, Viola arvensis, Polygonum aviculare as well as Poa annua, Elymus repens and Apera spica-venti. Chenopodium album was found in moderate and high numbers in maize, as well as the spring-germinating Polygonum species. Polygonum convolvulus escaped from or re-emerged after the chemical control at location Kuborn, while C. album was poorly controlled by the mechanical treatments. Alopecurus myosuroides plants with mature seeds were almost exclusively found in the South of Luxembourg. All 35 A. myosuroides seedling samples tested so far were resistant towards Stomp® Aqua (containing the microtubule assembly inhibitor pendimethalin). In case of Sigma® Maxx (containing the ALS inhibitors iodosulfuron+mesosulfuron), 2 out of 35 samples were sensitive and moderately resistant, respectively. 31 samples were resistant to Sigma® Maxx. 17 out of 35 samples were sensitive to Axial® (containing the ACC-ase inhibitor pinoxaden), while 18 samples were resistant to Axial®.

Im Pflanzenschutzamt der LWK Niedersachsen werden Samen von Alopecurus myosuroides im sogenannten „Biotest“ auf metabolische Herbizidresistenz und bei Bedarf auf weitergehende Target-site Resistenz (TSR) untersucht. Auf den norddeutschen Flächen brechen ganze Wirkstoffgruppen bei der Bekämpfung von Acker- Fuchsschwanz in allen Ackerbaukulturen weg, insbesondere auf Flächen, die seit Jahren intensiv in engen Getreidefruchtfolgen bewirtschaftet werden. Auf knapp 50 % der untersuchten Standorte wurde eine mittlere bis starke ALS-Resistenz gegenüber Mesosulfuron (enthalten in Atlantis WG, Atlantis OD, Atlantis flex, Niantic) nachgewiesen. Weitere Herbizide aus der Gruppe der ALS-Hemmer sind betroffen, so zeigen rund die Hälfte der gegenüber Mesosulfuron resistenten niedersächsischen Standorte auch eine deutliche Wirkungseinschränkung gegenüber den Wirkstoffen Foramsulfuron und Thiencarbazone (beide enthalten in MaisTer Power) in Mais. Fast die Hälfte der untersuchten Proben zeigt in Niedersachsen keine ausreichende Wirkung mehr für die Wirkstoffgruppe der DIM, Focus Ultra ist besonders betroffen und in einem geringeren Umfang auch Select 240 EC. Die Wirkstoffgruppen A (ACCase-Hemmer), und C (Photosynthese Hemmer) leiden ebenfalls unter einem erhöhten Resistenzrisiko bei den Gräserarten und das gleichzeitig in den Wintergetreidearten, Winterraps und den Sommerungen wie Kartoffeln, Zuckerrüben, Mais und Sommergetreide. In der Wirkstoffgruppe K zeigt der Wirkstoff Flufenacet bei der Acker-Fuchsschwanzbekämpfung ebenfalls erste Ermüdungserscheinungen. Dagegen werden bislang keine Herbizidresistenzen in den Wirkstoffgruppen E (Flumioxazin, Carfentrazone und Bifenox), F (Diflufenican, Clomazone und den Triketonen) sowie in G (Glyphosat), N (Prosulfocarb, Ethofumesat und den Synthetischen Auxinen (Quinmerac, Aminopyralid, Clopyralid) und den sogenannten Wuchsstoffpräparaten beobachtet. Weitere Herbizidresistenzen lassen sich für Alopecurus myosuroides nur durch Wirkstoffwechsel, Wirkstoffkombination und ackerbaulichen Maßnahmen vermeiden.

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.

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.)

Summary: Based on Hudson's collections sent to Linnaeus and currently preserved at LINN, lectotypes are designated for four species names published by Hudson: Alopecurus myosuroides, Festuca sylvatica (currently Brachypodium sylvaticum), Polygonum minus (currently Persicaria minor), and Scutellaria minor. [ABSTRACT FROM AUTHOR]

Black grass (Alopecurus myosuroides Huds.) is a highly competitive weed in winter wheat fields of China. Due to repeated use of acetolactate synthase (ALS) inhibitors, many A. myosuroides populations have evolved resistance to pyroxsulam in some wheat fields. Research was conducted to determine the molecular basis of herbicide resistance in the AH93 A. myosuroides population. Whole-plant dose–response assay confirmed that the AH93 population was resistant to pyroxsulam with a resistance index of 4.2. Cross- and multiple-resistance assays indicated that the AH93 population was cross-resistant to mesosulfuron-methyl and multiple-resistant to pinoxaden. Sequencing of the ALS and ACCase gene revealed that there was no target-site mutation in ALS, but Trp-2027-Cys and Cys-2088-Arg amino acid mutations in ACCase in the AH93 population. A malathion pretreatment study indicated that the AH93 population might have cytochrome P450–mediated herbicide metabolic resistance. This is the first report of pyroxsulam resistance in a multiple-resistant A. myosuroides population in China, and the Cys-2088-Arg mutation is the first reported case of an ACCase mutant conferring herbicide resistance in A. myosuroides.

The resistant level, mechainism of resistance of Alopecurus myosuroides against fenoxaprop- P-ethyl were determined. Results of the whole-plant dose-response test showed that population HN-05 from Henan Province had evolved high-level resistance against fenoxaprop-P-ethyl (52.2-fold). Using the gene sequencing method, two amino acid mutations at codon 2041 (Ile-Asn) and 2096 (Gly-Ala) were detected in the ACCase gene of the resistant population HN-05. Pre-treatment with the known metabolic inhibitor, piperonyl butoxide (PBO), enhanced the activity of fenoxaprop-P-ethyl (161.3- fold). So that the GR50 value (active ingredient) of fenoxaprop-P-ethyl to HN-05 is 5.4 g/hm2 . This study confirmed the resistance of A. myosuroides against the ACCase inhibitor, fenoxaprop-P-ethyl. The resistance mechanism were conferred by specific ACCase point mutations at amino acid position Ile-2041-Asn and Gly-2096-Ala and P450s-based metabolism. [ABSTRACT FROM AUTHOR]

Summary: The development of acetolactate synthase (ALS) tolerant sugar beet provides new opportunities for weed control in sugar beet cultivation. The system consists of an ALS−inhibiting herbicide (foramsulfuron + thiencarbazone‐methyl) and a herbicide‐tolerant sugar beet variety. Previously, the use of ALS‐inhibitors in sugar beet was limited due to the susceptibility of the crop to active ingredients from this mode of action. The postulated benefits of cultivation of the ALS‐tolerant sugar beet are associated with potential risks. Up to now, with no relevant proportion of herbicide‐tolerant crops in Germany, ALS‐inhibitors are used in many different crops. An additional use in sugar beet cultivation could increase the selection pressure for ALS‐resistant weeds. To evaluate the impact of varying intensity of ALS‐inhibitor use on two weed species (Alopecurus myosuroides and Tripleurospermum perforatum) in a crop rotation, field trials were conducted in Germany in two locations from 2014 to 2017. Weed densities, genetic resistance background and crop yields were annually assessed. The results indicate that it is possible to control ALS‐resistant weeds with an adapted herbicide strategy in a crop rotation including herbicide‐tolerant sugar beet. According to the weed density and species, the herbicide strategy must be extended to graminicide treatment in sugar beet, and a residual herbicide must be used in winter wheat. The spread of resistant biotypes in our experiments could not be attributed to the integration of herbicide‐tolerant cultivars, although the application of ALS‐inhibitors promoted the development of resistant weed populations. Annual use of ALS‐inhibitors resulted in significant high weed densities and caused seriously yield losses. Genetic analysis of surviving weed plants confirmed the selection of ALS‐resistant biotypes. [ABSTRACT FROM AUTHOR]

This paper presents the results of studies quantifying the effect of some of the tools available in an integrated weed control strategy focusing on problematic annual grasses in crop rotations with grass seed production. The paper presents the results of experiments demonstrating the influence of competitiveness of the crop on the development of annual grass weeds. The experiments quantify the influence of establishment at different row distance, plant density, sowing depth and cultivar type. The paper further presents the results showing how a change in establishment time from autumn to spring influences the germination rate of four important annual grasses. The study demonstrated that springtime establishment offers the opportunity to reduce problems with Apera spica-venti and Poa trivialis and to a lesser extent with Alopecurus myosuroides and Vulpia myuros. The study further showed that the false seedbed technique can be a very effective tool to reduce problems with annual grasses. The populations of two of the investigated species, P. trivialis and V. myuros, were reduced by almost 80% applying the false seedbed technique. Dependent on the density and species composition of annual grasses expected these IWM tools can be used in strategies to secure a high quality in grass seed production. [ABSTRACT FROM AUTHOR]

Highlights • Incremental changes to the life-cycle of A. myosuroides due to soil properties, when combined in a modelling approach, reveals them as important determinants of the within-field distribution of this species. • Scale-dependent correlations between A. myosuroides and soil properties observed in the field are an emergent property of the modelled dynamics of the A. myosuroides life-cycle. • Our model predicts areas of field that are vulnerable to A. myosuroides based on soil properties and so could support effective site-specific management of A. myosuroides within field. Abstract The patch spraying of weeds is an area of precision agriculture that has had limited uptake. This is in part due to the perceived risks associated with not controlling individual weeds. Nevertheless, the inherent patchiness of weeds makes them ideal targets for site-specific management. We propose using a mechanistic model to identify areas of a field vulnerable to invasion by weeds, allowing the creation of treatment maps that are risk averse. We developed a spatially-explicit mechanistic model of the life-cycle of Alopecurus myosuroides , a particularly problematic weed of cereal crops in the UK. In the model, soil conditions which vary across the field, affect the life-cycle of A. myosuroides. The model was validated using data on the within-field distribution of A. myosuroides on commercial farms and its co-location with soil properties. We demonstrate the important role played by soil properties in determining the within-field distribution of A. myosuroides. We also show that scale-dependent correlations between A. myosuroides and soil properties observed in the field are an emergent property of the modelled dynamics of the A. myosuroides life-cycle. Our model could therefore support effective site-specific management of A. myosuroides within fields by predicting areas that are vulnerable to A. myosuroides. The usefulness of this model in its ability to predict patch locations for A. myosuroides highlights the possibility of using similar models for other species where data are available on the response of the species to various soil properties. [ABSTRACT FROM AUTHOR]

BACKGROUND: Shortawn foxtail (Alopecurus aequalis Sobol.) is a competitive grass weed infesting winter wheat‐ and canola‐growing fields in China. In May 2016, a suspected A. aequalis resistant population AHTC‐06 that survived fenoxaprop‐P‐ethyl and mesosulfuron‐methyl applied at their field‐recommended rates was collected from a wheat field in Jinji County, Anhui Province, China. This study aimed to determine the resistance profile of this AHTC‐06 population to ACCase‐ and ALS‐inhibitors, and to investigate its mechanisms of resistance to fenoxaprop‐P‐ethyl and mesosulfuron‐methyl. RESULTS: Two mutations, a common Ile‐2041‐Asn (ACCase gene) and a very rare Pro‐197‐Tyr (ALS1 gene), were both identified in resistant individual plants. The homozygous subpopulation AHTC‐06F1 for the two mutations was generated, and it showed broad‐spectrum resistance to APPs, DENs, and ALS‐inhibiting herbicides of all five chemical families tested, with resistance index (RI) values that ranged from 2.2 to 36.5. In vitro ALS activity assays showed the ALS from the resistant population was insensitive to all the tested ALS inhibitors, with RI values ranging from 3.10 to 22.51. Pre‐treatment with piperonyl butoxide (PBO) and malathion significantly (P < 0.05) reversed the weed's resistance to fenoxaprop‐P‐ethyl and mesosulfuron‐methyl, respectively. Two P450 genes, c21190_g1 and c43350_g3, were constitutively overexpressed and mesosulfuron‐methyl‐induced upregulated in resistant plants, for which c43350_g3 was also fenoxaprop‐P‐ethyl‐induced upregulated. CONCLUSION: This study confirms the first case of a grass weed featuring broad‐spectrum resistance to ALS‐inhibiting herbicides due to a Pro‐197‐Tyr mutation in the ALS gene. Fenoxaprop‐P‐ethyl and mesosulfuron‐methyl resistances in AHTC‐06 plants were conferred by target site mutations and P450s‐based metabolism. © 2018 Society of Chemical Industry The Pro‐197‐Tyr mutation was identified in the ALS gene of a grass weed, Alopecurus aequalis, with multiple resistance of its plants conferred by target site mutations and P450s‐based metabolism. [ABSTRACT FROM AUTHOR]

Atlantis Star (mesosulfuron-methyl; iodosulfuron-methyl-sodium; thiencarbazone-methyl; mefenpyr-diethyl) is a new cereal herbicide to control blackgrass (Alopecurus myosuroides; sensitive and high infestation), brome grass (Bromus spec.), ryegrass (Lolium spec.), wild oat (Avena fatua), loose silky-bentgrass (Apera spica-venti L.), annual meadow-grass (Poa annua L.) and dicot weeds. Atlantis Star can be used in winter wheat, winter triticale, winter rye, winter durum wheat and spelt. The publication is based on efficacy trials from two years of spring application with Atlantis Star.

Cossack Star (mesosulfuron-methyl; iodosulfuron-methyl-sodium; thiencarbazone-methyl; mefenpyr-diethyl) is a new cereal herbicide to control blackgrass (Alopecurus myosuroides), ryegrass (Lolium spec.), wild oat (Avena fatua), loose silky-bentgrass (Apera spica-venti L.), annual meadow-grass (Poa annua L.) and dicot weeds. Cossack Star can be used in winter wheat, winter triticale, winter rye, winter durum wheat and spelt. The publication is based on efficacy trials from two years of spring application with Cossack Star.

Summary: Cover crops can suppress weeds within agricultural fields due to competitive and allelopathic effects. Glasshouse experiments were conducted to evaluate the relative proportions of allelopathic effects to the total weed inhibition. Six different cover crop species were combined with three weed species in the presence or absence of active carbon over a period of four weeks. Active carbon was used as an adsorbent for allelopathic substances in the soil. Our study revealed that the competition between cover crops and weeds shifted, possibly due to the minimisation of allelopathic effects by active carbon in the soil. We assume that the degree of cover crops allelopathic effects on weeds is species‐specific, both on the side of cover crops and on the weed side. The cover crops Raphanus sativus, Fagopyrum esculentum and Avena strigosa showed the highest allelopathic weed suppression with up to 28%. Additionally, Stellaria media turned out to be the most sensitive weed against allelopathic effects induced by all cover crops, except for Linum usitatissimum and Guizotia abyssinica. The knowledge about the contribution of competitive and allelopathic effects by cover crops would help to create cover crop mixtures with high weed suppressive ability. [ABSTRACT FROM AUTHOR]

There is an urgent need for more integrated weed management in commercial cereal production. However, there is gap in the general understanding of crop-weed interactions and the traits contributing to weed suppression by winter cereals. In this research, we measured the above-ground competitive traits crop height, leaf area index and early ground cover and below-ground allelopathic traits by quantification of benzoxazinoid (BX) content in the root zone by HPLC-MS/MS. A partial least squares regression was applied to identify the relative contribution of each trait to explaining the observed variance in weed biomass. The use of three winter cereals, wheat, triticale, and rye enabled us to cover a broad range of weed suppression strategies. For the first time, we were able to demonstrate a positive correlation between BX in plant material and phenoxazinoids in the soil. The highest concentration of BX in the rhizosphere was found at 3-10 cm. Furthermore, differences in crop weed interactions between wheat, rye, and dicotyledonous and monocotyledonous weeds were identified. Interestingly, there was no significant difference between the contribution of any single competitive or allelopathic trait to explain weed biomass. This is valuable information for the establishment of breeding programs for enhanced weed suppression by the cereal crops examined and suggests that an improvement of any of the competitive or allelopathic traits will lead to increased weed suppression. Furthermore, the transfer of traits from rye to wheat via triticale is promising as it may broaden the weed suppressive abilities of wheat. [ABSTRACT FROM AUTHOR]

The efficacy of different frequently used selective herbicides and their impact on weed community were assessed in the field experiment with cereal crop rotation in 2013-2016. All herbicide treatments provided effective weed control, but community composition changed after 4 years. The density of many weed species increased on the untreated plots. Annual grasses Apera spica-venti and Alopecurus myosuroides had temporal increase at plots treated with 2,4-d, florasulam and aminopyralid, but decline at plots treated with pyroxsulam and/or chlorsulfuron. Significant treatment effect was confirmed only for Shannon's index (H'), where the highest H' was found in untreated controls (1.83) and the smallest in plots treated with 2,4-d + florasulam + aminopyralid (1.61). The pyroxsulam + florasulam + aminopyralid showed the greatest efficacy on a broad spectrum of weeds while maintaining reasonable species diversity. [ABSTRACT FROM AUTHOR]

Abstract: BACKGROUND: A field‐evolved herbicide‐resistant weed population can represent a heterogeneous composite of subpopulations that differ in their susceptibility and responsiveness to herbicide hormesis. Variable hormesis responsiveness can result in selection for and against certain subpopulations under low herbicide doses, and this has the potential to contribute to the evolution of resistance. The relevance of this hypothesis at practical field rates was studied for two field‐collected acetyl‐coenzyme A carboxylase (ACCase) target‐site resistant (TSR) biotypes of Alopecurus myosuroides Huds. (haplotype Leu1781) exposed to three ACCase inhibitors. Herbicide dose responses were evaluated at the population level and at different subpopulation levels after the dissection of individual plants by herbicide selection and genotyping. RESULTS: The practical field rates of fenoxaprop‐P were lower than the observed hormetic doses in the resistant subpopulation, whereas the field rates of clodinafop and cycloxydim stimulated the shoot biomass in different resistant subpopulations by 21–38% above that of the control. Because variable dose levels induced hormesis in the different subpopulations, the practical field rates showed a significant potential to selectively enhance parts of a resistant field population, but did not impact or adversely affect other parts of the population. CONCLUSION: As a consequence of population heterogeneity, herbicide hormesis may impact resistance evolution in weeds at realistic use rates via the selective promotion of individual genotypes. However, the practical relevance of this phenomenon may be influenced by many factors, such as the herbicidal active ingredient used, as indicated in this study. © 2018 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Abstract: The sustainable management of unwanted vegetation in agricultural fields through integrated weed control strategies requires detailed knowledge about the maternal formation of primary seed dormancy, to support the prediction of seedling emergence dynamics. This knowledge is decisive for the timing of crop sowing and nonchemical weed control measures. Studies in controlled environments have already demonstrated that thermal conditions and, to some extent, water availability during seed set and maturation has an impact on the level of dormancy. However, it is still unclear if this applies also under field conditions, where environmental stressors and their timing are more variable. We address this question for Alopecurus myosuroides in south‐western Sweden. We quantified the effects of cumulated temperature and precipitation as well as soil water potential during the reproductive growth phase of A myosuroides on primary seed dormancy under field conditions. Empirical models differing in focal time intervals and, in case of soil water potential, focal soil depths were compared regarding their predictive power. The highest predictive power for the level of primary dormancy of A. myosuroides seeds was found for a two‐factorial linear model containing air temperature sum between 0 and 7 days before peak seed shedding as well as the number of days with soil water potential below field capacity between 7 and 35 days before peak seed shedding. For soil water potential, it was found that only the top 10 cm soil layer is of relevance, which is in line with the shallow root architecture of A. myosuroides. We conclude that for this species the level of dormancy depends on the magnitude and timing of temperature and water availability during the reproductive growth phase. Water availability appears to be more important during maternal environmental perception and temperature during zygotic environmental perception. [ABSTRACT FROM AUTHOR]

Resistance to the acetyl-coenzyme A carboxylase (ACCase)- and acetolactate synthase (ALS)- inhibiting herbicides in shortawn foxtail ( Alopecurus aequalis ) has been reported in wheat fields of eastern China. To better understand the distribution of the resistant populations and the occurrence of the target-site mutations, 74 populations collected from Anhui, Jiangsu and Shandong province were surveyed, and the ACCase and ALS gene fragments, encompassing all the documented mutant codon positions, were amplified and sequenced. Plants from 37 and 34 populations survived fenoxaprop-P-ethyl and mesosulfuron-methyl treatment at 62.1 g a.i. ha −1 and 9 g a.i. ha −1 respectively, with different survival rates. Twenty-seven populations exhibited multiple resistance to fenoxaprop-P-ethyl and mesosulfuron-methyl. Whole-plant dose-response experiments showed that the resistance index ranged from 6.2 to 167.8 for fenoxaprop-P-ethyl, and from 7.8 to 139.5 for mesosulfuron-methyl. Four ACCase (I1781L, I2041N, I2041T and D2078G) and four ALS (P197R, P197S, P197T and W574 L) resistance mutations were detected respectively. Individuals containing two amino acid substitutions were also found. D2078G and W574 L were predominant ACCase and ALS gene mutations respectively. This study has shown that fenoxaprop-P-ethyl and mesosulfuron-methyl resistance was prevalent in A. aequalis in eastern China, and target site mutations in the ACCase and ALS gene were one of the most common mechanisms. [ABSTRACT FROM AUTHOR]

Summary: The distribution of Alopecurus myosuroides (black‐grass) in fields is patchy. The locations of these patches can be influenced by the environment. This presents an opportunity for precision management through patch spraying. We surveyed five fields on various types of soil using a nested sampling design and recorded both A. myosuroides seedlings in autumn and seed heads in summer. We also measured soil properties at those sampling locations. We found that the patches of seed heads within a field were smaller than the seedling patches, suggesting that techniques for patch spraying based on maps of heads in the previous season could be inherently risky. We also found that the location of A. myosuroides patches within fields can be predicted through their relationship with environmental properties and that these relations are consistent across fields on different soil types. This improved understanding of the relations between soil properties and A. myosuroides seedlings could allow farmers to use pre‐existing or suitably supplemented soil maps already in use for the precision application of fertilisers as a starting point in the creation of herbicide application maps. [ABSTRACT FROM AUTHOR]

BACKGROUND: The efficacy of pre-emergence herbicides within fields is spatially variable as a consequence of soil heterogeneity. We quantified the effect of soil organic matter on the efficacy of two pre-emergence herbicides, flufenacet and pendimethalin, against Alopecurusmyosuroides and investigated the implications of variation in organic matter for weed management using a crop-weed competition model. RESULTS: Soil organic matter played a critical role in determining the level of control achieved. The high organicmatter soil had more surviving weeds with higher biomass than the low organic matter soil. In the absence of competition, surviving plants recovered to produce the same amount of seed as if no herbicide had been applied. The competition model predicted that weeds surviving pre-emergence herbicides could compensate for sublethal effects even when competing with the crop. The ED50 (median effective dose) was higher for weed seed production than seedling mortality or biomass. This difference was greatest on high organic matter soil. CONCLUSION: These results showthat the application rate of herbicides should be adjusted to account for within-field variation in soil organic matter. The results from the modelling emphasised the importance of crop competition in limiting the capacity of weeds surviving pre-emergence herbicides to compensate and replenish the seedbank. [ABSTRACT FROM AUTHOR]

Summary: Mapping weed densities within crops has conventionally been achieved either by detailed ecological monitoring or by field walking, both of which are time‐consuming and expensive. Recent advances have resulted in increased interest in using Unmanned Aerial Systems (UAS) to map fields, aiming to reduce labour costs and increase the spatial extent of coverage. However, adoption of this technology ideally requires that mapping can be undertaken automatically and without the need for extensive ground‐truthing. This approach has not been validated at large scale using UAS‐derived imagery in combination with extensive ground‐truth data. We tested the capability of UAS for mapping a grass weed, Alopecurus myosuroides, in wheat crops. We addressed two questions: (i) can imagery accurately measure densities of weeds within fields and (ii) can aerial imagery of a field be used to estimate the densities of weeds based on statistical models developed in other locations? We recorded aerial imagery from 26 fields using a UAS. Images were generated using both RGB and Rmod (Rmod 670–750 nm) spectral bands. Ground‐truth data on weed densities were collected simultaneously with the aerial imagery. We combined these data to produce statistical models that (i) correlated ground‐truth weed densities with image intensity and (ii) forecast weed densities in other fields. We show that weed densities correlated with image intensity, particularly Rmod image data. However, results were mixed in terms of out of sample prediction from field‐to‐field. We highlight the difficulties with transferring models and we discuss the challenges for automated weed mapping using UAS technology. [ABSTRACT FROM AUTHOR]

Herbicide resistance has become an increasing problem, and at the same time pesticide usage is declining due to stringent EU pesticide legislation which aims to reduce the impact on environment and human health. For these reasons, new alternative integrated weed management approaches are becoming increasingly relevant. Formulations based on Brassica defatted seed meals (DSMs) and glycerin, have previously been shown to be effective in reducing the germination of lettuce seed. In this work five DSMs, formulated with and without crude glycerin, were chosen for in vitro and glasshouse experiments: i) Brassica nigra , ii) Brassica tournefortii , iii) Eruca sativa , iv) Rapistrum rugosum and v) Sinapis alba . Black-grass ( Alopecurus myosuroides ), a weed demonstrating extensive herbicide resistance, was used as a target, and the germination inhibition caused on this weed by Brassica defatted seed meals was assessed. In both in vitro and in vivo experiments, the most effective DSM for inhibiting germination of both lettuce and black-grass seeds was the sinigrin containing DSM, Brassica nigra . The aim of the manuscript was to suggest a new high value application for Brassicas derived DSM as a co-products from the vegetable oil production chain. The proposed treatments could represent an interesting and 100% novel natural alternative to the conventional herbicides. [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.)

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.)

In dose-response experiments and by molecular analyses the reaction of a black grass biotype (Alopecurus myosuroides) with target site resistance to ACCase inhibitors (Ile1781-Leu) was examined for the response to clethodim and cycloxydim and compared to the responses of the homozygous and heterozygous subpopulations. To decipher the population into the homo- and heterozygous sub-populations, individual plants of the resistant biotype were analyzed for the haplotype Leu1781 by means of SNP analytics (pyrosequencing). For the entire population, significant different resistance factors (RF) of 8 and 153 resulted for clethodim and cycloxydim, respectively. For the heterozygous sub-population a RF of 6 was estimated for clethodim and 118 for cycloxydim. For the homozygous sub-population a RF of 10 for clethodim and 136 for cycloxydim was estimated. The RF between the homo- and heterozygous sub-populations for each herbicide were, however, not significantly different. Despite this, a tendency of the heterozygous sub-population being less resistant was indicated. Therefore, it is hypothesized that the selection of resistance depends not only on the herbicide used, but on the frequency of the genotypes in a field population. Furthermore, the significant different reaction of black grass with the haplotype 1781 to both tested herbicides reflects the meaning of the individual constellation of active ingredient, resistance mechanisms and genotype for selection and spread of resistance.

SYD 11720H is a new, selective herbicide developed by Syngenta agro for grass weed and dicot control in winter cereals. It is formulated as suspoemulsion with 604,5 g active ingredient per liter and contains the active ingredients Prosulfocarb (600 g/L) and Pyroxsulam (4,5 g/L), as well as the safener Cloquintocet-mexyl (4,5 g/L). SYD applied 11720 H with a rate of 4.0 L/ha in combination with an additive in order to stabilize the efficacy under adverse conditions. The essential innovation of SYD 11720H is the combination of a primarily soil-active (Prosulfocarb) and leaf-active (Pyroxsulam) active ingredient. This allows a longer application window or a previous application regardless of weather conditions. The product has no carry over limitations and allows the full flexibility in recropping. The major benefit which is of particular importance is the good efficacy against winter annual grass weeds and dicotyledonous species. The registration is requested for the post-emergence application use in autumn in winter wheat, winter rye, and winter triticale from the 1-leaf growth stage (BBCH 11) to beginning of tillering (BBCH 21) of the crop.

With substantial work on the formulation, Gowan offers a new herbicide (GWN-3189 B) based on Triallate for use on winter wheat, winter barley, winter rye, winter triticale and spring barley. GWN-3189B will be applied from pre-emergence to early post-emergence of the crop and offers a broad spectrum against grass-weeds. GWN-3189 B is selective on all cereal species. As soil herbicide GWN-3189 B offers interesting alternatives in grass-weed resistance management. The efficacy on grass weed, especially on Alopecurus myosuroides (blackgrass), Apera spica venti (silky bentgrass) and Lolium multiflorum (italian ryegrass) is demonstrated with results of field trials performed in France, Great Britain and Germany.

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.

Atlantis FLEX (Mesosulfuron-methyl; Propoxycarbazone-sodium; Mefenpyr-diethyl) is a new cereal herbicide to control blackgrass (Alopecurus myosuroides), ryegrass (Lolium spec.), brome grass (Bromus spec.), wild oat (Avena fatua), loose silky-bentgrass (Apera spica-venti L), annual meadow-grass (Poa annua L.) and dicot weeds. Atlantis FLEX can be used in winter wheat, winter triticale, winter rye, winter durum wheat and spelt. The publication is based on efficacy trials from two years of spring application with Atlantis FLEX. It will be shown, that Atlantis FLEX generates a good to excellent efficacy against grass-weeds.

In field experiments the control of blackgrass (Alopecurus myosuroides, Huds.) in oilseed rape using clethodim (Select EC 240) and cycloxydim (Focus Ultra) with and without subsequent treatments with propyzamide (Kerb FLO) was tested at 6 locations in North and South Germany with assumed resistance problems. The field experiments were accompanied using molecular analysis leaf samples from the plots to seize the occurrence of black-grass with the Leu 1781 haplotype and to determine the frequency of the genotypes. The goal of the trials was to correlate the successes of blackgrass control with the occurrence of hetero- and homozygous resistant genotypes. It was shown in greenhouse trials that clethodim selects the haplotype Leu1781 more weakly (and it shows a higher partial efficacy) than cycloxydim and that heterozygous plants have a lower resistance factor than homozygous plants. The question raised whether the frequency of heterozygous plants has influence on increased efficacy of clethodim under field conditions. At 5 sites target-site resistance was detected. At one location the high proportion of heterozygous plants correlated positive with relative higher control using Select EC 240 (80%) compared to Focus Ultra (0%). At two locations with high proportion of homozygous resistant plants Select EC 240 and Focus Ultra treatments without subsequent treatments with Kerb FLO were not sufficient in solo variants. The subsequent treatments with Kerb FLO provided partly, but not sufficient control of black-grass. At one location no resistance was identified. The effect of Select EC 240 and Focus Ultra to control black-grass were comparable high in all variants with and without subsequent treatments of Kerb FLO. The investigations showed clearly a higher degree of control by plants with the haplotype Leu1781 by the active substance clethodim and pointed out the fact that the frequency of resistant genotypes (homo vs. heterozygous resistant plants) has a clear influence on the resistance selection. The use of DIMs at locations suspected to be resistant should be assured only with the help of propyzamide and nonchemical measurements (e. g. ploughing, crop rotation). The results also indicate that it is necessary to assess resistance mechanisms in resistance research individually depending on the active ingredients, inheritance and weed species.