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In konventionellen Ackerbausystemen werden derzeit überwiegend Herbizide zur Kontrolle von Unkräutern eingesetzt. Der Einsatz von Herbiziden wird wegen unerwünschter Wirkungen auf abiotische Ressourcen sowie die Biodiversität kritisch diskutiert. Um ihren Einsatz zu reduzieren, müssen mittelfristig alternative Lösungen gefunden werden. Als Alternative kommt UV-C Strahlung in Frage. Diese wirkt ab einer bestimmten Dosis irreversibel zellschädigend, wodurch das Wachstum von Pflanzen reduziert wird. Der wichtigste Parameter der UV-C Applikation ist die Dosis, die sich aus der Strahlungsstärke des Strahlfeldes und der Dauer der Bestrahlung ergibt. Ziel der Untersuchungen war es, eine UV-C Dosis zur Unkrautkontrolle zu finden, mit der das Wachstums von Unkrautpflanzen beeinträchtigt wird. Am Beispiel von Raphanus sativus wird eine Dosis-abhängige Wachstumshemmung der UV-C Strahlung gezeigt. Die höchste Reduktion im Vergleich zur unbehandelten Kontrolle betrug 93 % der Trockenmasse. Neben der UV-C Dosis hatte auch der zeitliche Abstand zwischen wiederholten Bestrahlungen einen Einfluss auf die Biomasseentwicklung der Pflanzen.

Mehrjährige Blühpflanzenmischungen werden als eine vielversprechende Möglichkeit zur Förderung der Biodiversität und zum Erhalt von Ökosystemdienstleistungen in Agrarökosystemen betrachtet. Um festzustellen, welches Angebot an Blüten und Samen eine mehrjährige Blühmischung während der Vegetationsperiode und über die Standjahre bereitstellt, wurden Blütendokumentationen durchgeführt und Trichter-Samenfallen in Feldversuchen platziert. Zwischen 2014 bis 2018 wurden jedes Jahr Parzellen mit der Blühpflanzenmischung angesät und die Pflanzendichte artspezifisch gezählt. Blühende Arten wurden in einem zweiwöchigen Rhythmus im Jahr 2019 und 2020 dokumentiert und Trichter-Samenfallen wurde im Jahr 2019 und 2020 wöchentlich entleert und im Jahr 2016 und 2017 monatlich. Unsere Studie zeigt, dass die Blühmischung ein kontinuierliches Angebot an Blüten und Samen bietet, die zweijährigen Blühpflanzenbestände die größte Vielfalt an Blüten lieferte sowie die meisten Samen. Im Frühsommer deckt die Spontanvegetation das Angebot an Blüten und Samen. In den Spätsommermonaten (ab Mitte August bis Oktober) komplementieren die Blühpflanzenmischungsarten das Blütenangebot und dominieren das Nahrungsangebot an Samen für die Fauna. Die Gesamtsumme der auf den Flächen verbleibenden Samen nimmt mit zunehmendem Standjahr der Blühpflanzenmischung ab.

Seit 1950 sind sowohl die Artenvielfalt von Ackerunkräutern als auch die Arthropoden und Vögel in Deutschland und darüber hinaus stark zurückgegangen. Es stellt sich die Frage, welche Rolle Ackerunkräuter bei der Unterstützung der Artenvielfalt, insbesondere von Arthropoden und Vögeln, spielen. In einer Literaturrecherche wurden 51 Ackerunkrautarten und 3 Unkrautgattungen, welche in Deutschland häufig vorkommen, auf ihre Rolle als Nahrung und Lebensraum für die Fauna untersucht. Direkte und indirekte Verbindungen zwischen Ackerunkräutern und Vögeln sowie Arthropoden wurden anhand von Daten aus der veröffentlichten Literatur gezählt. Es wurden 5180 Verbindungen zwischen den Ackerunkräutern und Arthropoden bzw. Vögeln gefunden. Die Daten weisen darauf hin, dass Ackerunkräuter nicht nur die landwirtschaftliche Erzeugung behindern, sondern auch eine Vielzahl von Ökosystemleistungen unterstützen.

Pelargonic Acid (PA) is a naturally occurring fatty acid that is used as a bio-based herbicide to control both annual and perennial weeds. In this particular study, we investigated the effects of influencing factors on the efficacy of PA on Cirsium arvense (L.) Scop. under semi-field and greenhouse conditions. For this purpose, we examined the effects of different timings, application volumes, and adjuvants of PA to control C. arvense. Two application volumes (10.9 kg PA at 200 L and 400 L water/ha), and five plant growth stages were tested in a semi-field experiment. In a greenhouse experiment, Paraffin oil, as an adjuvant, was added to both PA application volumes to evaluate the possible increase in PA herbicidal efficacy. Our results showed that 10.9 kg PA in the volume of 400 L water/ha improved the PA efficacy. Paraffin oil, as an adjuvant, can enhance PA efficacy. The most effective times to control using PA were early-elongation and the seven-to-ten leaf stages for C. arvense. We conclude that 10.9 kg PA with an application volume of 400 L/ha and added adjuvant is a mixture with a herbicidal potential when applied at an earlier stage of C. arvense.

Creeping perennial weeds are widely distributed on arable fields. The common control practices are intensive inversion tillage and chemical herbicides. However, these methods are under pressure as they negatively affect non-target species and the environment. The objective of the SusCrop-ERA-NET funded European project ‘AC/DC-weeds’ is to implement agroecological management for creeping perennials in arable farming. Focusing on three important perennial species in central and northern Europe (Sonchus arvensis, Cirsium arvense and Elymus repens), the project addresses these species using and combining different methods. In research, the existing information is checked for the contribution to knowledge. New experimental approaches focus research gaps on biology as well as tools and technologies to enable an agro-ecological management. Paying attention to the needs of farming should raise the probability for a practised agro-ecological management of creeping perennials.

Mehrjährige Wurzelunkräuter sind im Ackerbau von großer Bedeutung. Der Beitrag stellt Erfahrungen landwirtschaftlicher Praxisbetriebe zu Vorkommen und Managementmaßnahmen von Wurzelunkräutern in der Praxis vor. Die Ergebnisse stammen aus einer im Winter 2020/21 durchgeführten und auf Fragebögen basierenden Erhebung. Konventionell (51 %), konservierend (32 %) und ökologisch wirtschaftende Betriebe (17 %) haben an der Umfrage teilgenommen. Die Ackerkratzdistel (Cirsium arvense) tritt als bedeutendste Art im Praxisanbau auf. Quecke (Elymus repens), Ackerwinde (Convolvulus arvensis) und Ackerschachtelhalm Equisetum arvense) kommen bei über 70 % der teilnehmenden Betriebe vor. Die reduzierte Ertragsmenge und -qualität, die teure und zeitaufwändige Kontrolle, die Ausbreitung des unterirdischen Wurzelsystems im Boden und das beeinträchtige Erscheinungsbild der Flächen werden als negative Aspekte des Auftretens der Wurzelunkräuter genannt. Insgesamt schätzen die Praxisbetriebe die Kontrolle mehrjähriger Wurzelunkräuter zukünftig als problematisch ein. Der Einsatz der Fruchtfolge als Kontrollmaßnahme mehrjähriger Wurzelunkräuter erscheint aus Sicht aller teilnehmenden Betriebe wirksam. Ökologische Betriebe schätzen die mechanische Bekämpfung als effizientes Werkzeug zur Kontrolle der Wurzelunkräuter. Die chemische Bekämpfung wird hingegen unter konservierend und konventionell wirtschaftenden Betrieben als wirksamste Managementmethode genutzt. Nach dem Auslaufen der Wirkstoffgenehmigung für Glyphosat Ende 2022 wird sich das Unkrautartenspektrum konservierend und konventionell wirtschaftender Betriebe verändern. In erosionsgefährdeten Gebieten sind ökologisch wirtschaftende Betriebe aufgefordert die wendende Bodenbearbeitung zu reduzieren. Die Kombination aus mechanischer Störung und Konkurrenz kann zur effizienten Kontrolle der Wurzelunkräuter aller Betriebsformen beitragen.

Perennial weeds like Cirsium arvense ensure their lifeform by their subterranean storage organs. Current control essentially relies on inversion tillage and herbicides (especially glyphosate). One alternative is the so-called “Kverneland Horizontal Root Cutter”. This machine fragments adventitious roots and cuts them off from belowground shoots and deep reaching root parts via horizontally arranged sheers, subsequently leading to a depletion of reserves. We conducted an experiment between September 2019 and September 2021 on a field carrying C. arvense but no crop. Treatments differed in terms of use frequency and working depth of the “Root Cutter”. Six cuts per year (twelve in total) reduced the number of shoots by approximately 75% and the aerial expansion of thistle patches by approximately 90%. Lower cut frequencies decreased aerial expansion but failed to reduce number of shoots. HPLC root carbohydrate measurements revealed an exhaustion of reserves by root cutting. Total sugars and inulin reduction increased with cutting frequency. Based on the presented results the “Kverneland horizontal root cutter” can serve as a possible replacement for ploughing for the purpose of combating perennial weeds like C. arvense.

Agro-ecological farming takes a significant shift in farmers’ knowledge and behaviour. Video has become an important part of education and dissemination. Here, we present an instructional video development process for the visualizing of C. arvense growth. The scientific literature on biology, distribution and control measures of C. arvense has been collected and pooled in an indexed database. The next step was to create a design document. The heart of the video development process is ‘Storyboarding’. A storyboard is a graphic representation of how the video will unfold, scene by scene. After finishing the storyboard, a professional designer planned the onscreen visuals and recorded a first draft based on the storyboard. When the entire video is established, any gaps or lulls in onscreen visuals became clear. Visualizing the spatial spread of C. arvense roots belowground will enable farmers and advisors to comprehend the growth and reproduction of C. arvense.

Silage maize is an important arable crop in Germany. Echinochloa crus-galli is one of the main weed species in this crop. Herbicide treatment, a common practice by conventional maize farmers to control this weed, may cause many negative impacts on non-target species and the wider environment. Post-dispersal seed predation is an important ecosystem service for weed control, but its value is rarely known. To raise social awareness, we aim to estimate the economic benefits of this ecosystem service. The extent of benefits that farmers can receive from the post-dispersal seed predation depends greatly on how farmers control weeds. By using an on-farm pesticide survey, the herbicide application patterns for Echinochloa crus-galli control in maize in the north-eastern Germany is analysed. Based on this, and by using economic surplus and field data from cage experiments, this case study estimated the value of post-dispersal seed predation of Echinochloa crusgalli in 2013 maize fields in Mecklenburg-West Pomerania. This represents one of the first attempts of economic valuation of this ecosystem service.

Creeping perennial weeds have strong negative impacts on arable production. The common control practices are intensive inversion tillage and chemical herbicides. However, these traditional methods negatively affect non-target species and the environment. The objective of the SusCrop-ERA-NET funded European project ‘AC/DC-weeds’ is to implement agro-ecological management for creeping perennials in arable farming. The overall aim of this project is to reduce plough-tillage in organic and conventional farming, and to replace glyphosate in the latter system. From 2019 to 2022, this project involves seven partners from five European countries. Focusing on three important perennial species in central and northern Europe (Sonchus arvensis, Cirsium arvense and Elymus repens), AC/DC-weeds will thoroughly study the ecology and agronomical management of these species through systematic literature reviews and experiments. Novel agro-ecological management of these species is examined in field experiments and semifield approaches. Innovative technology will be used to identify and monitor the distribution of these weeds on fields. Qualitative models are developed to make use of existing knowledge and expertise of the influences on perennial infestations in management decisions. A graphic web tool will enable visualization of the growth of the species and the effects of weed management. Environmental and economic evaluations on different weed management accompany the experimental and modelling work.

Der Gemeine Windhalm Apera spica-venti (L.) hat sich in den zurückliegenden Jahrzehnten zu einem der wichtigsten Ungräser in Europa entwickelt. Europaweit sind für Windhalm jedoch zunehmende Resistenzfälle besonders gegenüber Herbiziden aus der Gruppe der ALS-Inhibitoren bekannt. Die vorliegenden Dosis-Wirkungs-Versuche zielen darauf ab die Wirksamkeit ausgewählter Herbizide gegenüber dem Gemeinen Windhalm in Mecklenburg-Vorpommern zu quantifizieren und Dosis-Wirkungs- Beziehungen zu prüfen. Zu diesem Zweck wurde im Frühjahr 2019 ein Biotest mit 19 Windhalmpopulationen von Feldern in Mecklenburg-Vorpommern durchgeführt. Unter standardisierten Gewächshausbedingungen wurde die Wirkung der vier Herbizide Axial 50®, Herold SC®, Broadway® und Husar Plus® auf die 19 Populationen getestet. Für die 19 Windhalmpopulationen wurden für die Herbizide Axial 50®, Broadway® und Husar® Wirkungen >95 % ermittelt. Für Herold SC® wurden hingegen unter den getesteten Populationen anhand der mittleren Wirkung bei voller Aufwandmenge Wirkungsschwächen nachgewiesen. Die ED50-Werte variieren zwischen den Herbiziden Axial 50®, Broadway®, Husar Plus® und Herold SC®. Der höhere mittlere ED50-Wert, der für Herold SC® ermittelt wurde, deutet darauf hin, dass nur bei maximaler Dosis ausreichende Wirkung gegenüber dem Gemeinen Windhalm besteht.

Today farmers manage arable weeds with chemical tools or mechanical tillage practices. While the heavy reliance on synthetic herbicides in conventional arable farming is under discussion, the environmentally driven trend towards reduced tillage as a climate-smart agricultural practice becomes more prominent. These trends demand for alternative control methods of weeds. This greenhouse study investigates the control of 21 arable weeds with four natural substances. The experimental setup compared an untreated control with four natural substances (acetic, citric and pelargonic acid and magnesium chloride), and glyphosate was used as the common active ingredient for stubble and presowing herbicide applications. The level of necrotisation (0-100%) was used to assess the efficacy of herbicide treatment. The efficacy differs substantially among the bio-based herbicides. For all natural substances, pelargonic acid has the highest mean efficacy for controlling the weeds tested in this experiment. For most weeds, however, the efficacy of natural substances is much lower compared to glyphosate. Nevertheless, the results indicate that natural substances as bio-based herbicides have the potential to offer an increased target specificity and rapid degradation in the soil. We found a high efficacy of pelargonic acid for controlling Brassica napus.

Mehrjährige Blühmischungen für die Biogasproduktion könnten durch ihre breite Standortanpassung auch in ertragsschwachen Regionen eine Alternative zum Maisanbau sein, wenn sie durch wüchsige Arten hohe Erträge liefern und nebenbei die Biodiversität fördern. Um die Anbaueignung einer Wildpflanzenmischung auf sandigem Boden hinsichtlich der Entwicklung des Artenreichtums der ausgesäten Wildarten über eine dreijährige Nutzungsdauer zu prüfen, wurden im Frühjahr 2015 an zwei Standorten in Brandenburg Feldversuche mit der Wildpflanzenmischung „BG 70“ angelegt. Die Mischung ist mehrjährig, enthält 23 Arten und wurde speziell für die Biogasproduktion entwickelt. Von 2015 bis 2017 wurden jedes Jahr Parzellen mit der Wildpflanzenmischung angesät. Die gewachsene Vegetation wurde in mehreren Erhebungsterminen artspezifisch gezählt. Eine sinkende Biodiversität der Wildarten über die Standjahre wurde festgestellt. Ab dem zweiten Standjahr dominierten die perennierenden Arten Centaurea nigra und Artemisia vulgaris aus der Blühmischung. Die Individuenzahlen der Wildarten war zu Beginn des ersten Standjahr gering und sank weiter. Überraschenderweise sank auch die Unkrautdichte über die Jahre. In den Spätsommermonaten (August und September) komplementieren die Wildarten das Nahrungsangebot für Tiere zu der natürlichen gewachsenen Vegetation.

Hinsichtlich der Unkrautsamen-Hygiene von Gärresten aus Biogasfermentern gibt es noch ungelöste Fragen. Die Fähigkeit von Samen, feucht-warme Bedingungen zu überleben, ist artspezifisch, und Prognosen für nicht getestete Arten abzugeben ist schwierig. In dieser Arbeit wird untersucht, ob die Herkunft der Art Rückschlüsse auf die Temperaturtoleranz ihrer Samen gibt. Hier wurden Samen von sechs Arten der Familie der Süßgräser getestet: Alopecurus myosuroides, Cynodon dactylon, Echinochloa crus-galli, Panicum dichotomiflorum, Setaria viridis und Vulpia myuros. Die Samen wurden bei 42°C in Wasserbädern bis zu 12 Tagen inkubiert. In regelmäßigen Zeitabständen wurden Samen entnommen und ihre Keim- und Lebensfähigkeit geprüft. Es wurden 4-parametrische Zeit-Wirkungskurven modelliert. Ein Vergleich der Arten und Biotypen anhand der mittleren Inaktivierungszeit (ET50-Werte) zeigte, dass Samen von C4-Gräsern, die aus wärmeren Florenzonen stammen, länger überlebten und besser keimten als Samen der C3-Grasarten. Bei Gräsern, die auch in tropischen Regionen vorkommen, lag der ET50-Wert bei über fünf Tagen. Die Studie zeigt, dass die evolutionären Bedingungen, die zur heutigen weltweiten Verbreitung der Gräser führten, für eine Abschätzung der Überlebensfähigkeit ihrer Samen genutzt werden können. Betreiber von Biogasanlagen sollten sich des Risikos bewusst sein, mit dem Gärrest Grassamen, insbesondere von Hirsen, zu verbreiten.

Mais ist die zweitwichtigste Kulturpflanze in Deutschland. Die genutzten Anbauverfahren im Mais variieren zunehmend, sodass neben der klassisch wendenden Bodenbearbeitung, vermehrt die nicht-wendende Bodenbearbeitung genutzt wird. Mais wird zudem als Teil einer Fruchtfrequenz oder in Selbstfolge angebaut. Die Folgen des veränderten Managements auf die Eigenschaften der Unkrautarten sind unklar. Es wird jedoch angenommen, dass ein entsprechendes Management mit bestimmten Unkrauteigenschaften assoziiert ist. Die wendende Bodenbearbeitung begünstigt scheinbar konkurrenzstarke Unkrauteigenschaften als die nichtwendenden Bodenbearbeitung. Weiterhin wird vermutet, dass konkurrenzstarke Eigenschaften eher durch den Anbau von Mais in Selbstfolge als durch den Anbau in Rotation gefördert werden. Dies wurde mit Hilfe einer modernen RLQ-Analyse getestet. Als Datengrundlage für diese Analyse wurden Feld- und Unkrautdaten aus einem deutschlandweiten Unkrautmonitoring im Mais 2017 und 2018 sowie ein Datensatz zu Unkrauteigenschaften (Raunkiear Lebensformen, Lebenszyklus, Leaf-Height-Seed Strategien, Phenology, Klassische Verwandschaftsgruppen der Unkräuter sowie deren Neigung Herbizidresistenzen zu bilden) aus anderen Studien zusammengestellt. Die Ergebnisse zeigen, das unabhängig vom Management im Mais, konkurrenzstarke Unkrauteigenschaften, wie Therophyten, Arten mit hoher Affinität zu nährstoffreichen Böden, große Blattflächen, hohe Pflanzenhöhe und ein schweres Samengewicht vorkommen können. Managementfaktoren können jedoch die Gruppierung bestimmter Unkrauteigenschaften fördern. So werden, entgegen der Annahme, konkurrenzstarke Unkrauteigenschaften eher der nicht-wendenden als der wendenden Bodenbearbeitung zugeordnet. Wie erwartet, kann der Anbau von Mais in Selbstfolge eine Anpassung der Unkrautarten an die Bedingungen im Mais fördern.

FlorSys is a model that aims to quantify the effects of the agricultural systems on the weed demography. With successful parameterization, it can be used to predict weed growth. FlorSys is a multi-species-model which was developed at INRA in Dijon (France). The model is based on the representation of the weed life cycle. The consecutive stages are connected by demographic functions with species-specific parameters. They are modified by the impact of the agricultural system, the interactions with environmental conditions and the measures against weeds. FlorSys can be used in a wide range of conditions. We want to test FlorSys as parameterized in Burgundy (France) in Northeastern Germany in order to check and improve its applicability here. Therefore, we will conduct trials for the parameter estimation of weed species in the next years. We will use species that have already been parameterized in order to compare different geographic sources, and to complement them with species which are important in Northern Germany. We introduce the FlorSys model and report about greenhouse and semi-field experiments.

Glyphosate is the worldwide mostly used herbicide substance. Glyphosate use in arable cropping is under strong discussion in scientific and public communities. In the present study, we investigated the use of glyphosate from 15 farms in four districts in North German arable farming from 2005 until 2014. Objective of our research is to reveal influencing factors on glyphosate use intensity. The farm structures differ between two West districts (Diepholz, Uelzen) and two East districts (Fläming, Oder-Spree). We used the Standardised Treatment Index (STI) to quantify pesticide use intensity. We used multiple regressions to estimate the relationship between farm characteristics and glyphosate use. Glyphosate use intensity differs substantially between the study districts and crops. Farmers in the Eastern districts (Fläming and Oder-Spree) used significantly larger amounts of glyphosate. We further proved that the variability of glyphosate use was mainly influenced by the factor “Farm”. Moreover, we could show that glyphosate use is significantly influenced by the factors tillage, farm type, farm size and on-farm labour. Non-inversion tillage and glyphosate use co-incidences mainly on large farms in the East German districts. Hence, we conclude that these farms either regionally adapt their cropping systems due to climatic reasons or for economic profit.

Weed seeds can enter the biogas reactor by the harvest of biomass or by animal manure. All seeds that enter the biogas process chain and survive anaerobic digestion can be spread with the digestate. The inactivation of seeds in the biogas reactor is mainly due to temperature. In comparison of a laboratory-scale biogas reactor and a water bath experiment, we tested the contribution of temperature in the inactivation of seeds from one hardseeded and one non-hardseeded species. On average, as few as 20 % of the tomato seeds, which are used as an indicator species for the sanitation of fermentation plants, survived the maximum exposure time in the reactor and water bath. In the reactor the seeds lost their viability quicker than could solely be explained by temperature. Viability of the hardseeded species, Melilotus albus, declined to 70 % after the maximum exposure time of 12 days. The decline was similar in water baths and reactor. Inactivation of M. albus seeds was mainly due to temperature. For tomato seeds, factors other than temperature must have contributed to inactivation. Tomato appears to be no appropriate indicator for inactivation of (hardseeded) seeds in biogas reactors.

Weed species easily establish in crops with a similar life cycle. Especially mono-cropping provides best conditions for such weeds. In maize this is true for Echinochloa crus-galli, which is a C4 plant and one of the worst weeds worldwide. In Germany E. crus-galli is one of the few typical weed species in maize. When recurrent herbicide treatments are applied, development of herbicide resistance is likely. Since maize is typically only treated once with herbicides, later germinating weeds can escape and produce seeds. These escaping weeds are not selected for herbicide resistance. Hence, they still have a more sensitive gene pool. E. crus-galli emerges with the highest density in spring and continues to germinate over the whole vegetative period of maize. In that way the early germinating biotypes are selected for herbicide resistance while the later germinating biotypes are not. To avoid the reproduction of E. crus-galli effort is made to suppress these later germinating weeds. Using undersown cover crops is one way to do that. We hypothesize that suppressing the later germinating biotypes enhances the development of herbicide resistance. We simulated the development of herbicide resistance in populations of E. crus-galli, composed of sensitive and resistant biotypes, in a continuous maize cropping system. We used the model PROSPER for our simulations. We assumed three levels of suppression of the later germinating weeds (0%, 30%, and 100%). The results show a faster development of herbicide resistance, when the later germinating individuals are suppressed. Nevertheless, the suppressive effect of undersown crops is able to lower the weed density even with high resistance level in the population.

Glyphosate is a non-selective, broad-spectrum, systematic herbicide that is the world’s most widely used herbicide since its introduction in the 1970s as a pre-plant, post-directed and post-harvest herbicide application with further technological developments leading to its use within glyphosate resistant crops (GRCs) as of the 1990s. In countries around the world, weed shifts have accompanied weed management systems employing glyphosate products. The farmer actions and weed reactions that have contributed to these weed shifts will be discussed. Evidence of glyphosate-induced weed shifts has not yet been documented in Germany, but through consideration of the conditions that have lead to glyphosate-induced weed shifts elsewhere the outlook for Germany will be assessed. An ongoing research project will be introduced in which weed monitoring is being employed to find out if glyphosate-induced weed shifts can be identified in northeastern German arable farm fields and in which field experiments are also being conducted to further explore the reactions of weed communities and populations under the intensive application of glyphosate products.

Arable weeds accompany arable land use – we define them based on their affiliation to ar able systems. They are adapted to such a degree that most of them cannot exist without arable land use. Weeds are part of the total biodiversity on arable fields, as primary producers they are basic for important functions within the ecosystem. This paper elaborates the relevance of species diversity in arable weeds for their management. Arable systems can be regarded for the number of different methods for preventive and direct weed control which are realized. Historical arable land use is roughly divided into three periods, which differ concerning the diversity of weed management and the occurring diversity in weed species. Obviously divers weed management in arable systems and diversity in weed species depend on each other, this is illustrated with a simple abstract picture. Arable systems, which are characterised by simpleness, favor the domination of few species which ensure an effective use of the resources within the ecosystem. One consequence under continuous pressure of an overused tool in weed management is that the genetic diversity within a dominating weed population is exploited to ensure this resource use. Current herbicides represent this tool – the results are herbicide resistant biotypes within the weed populations. Species diversity in arable weeds as a rationale within arable production can assist to prevent this development.

This study is a component of the CORE Organic Plus PRODIVA project, a collaboration between international weed research institutions, which aims to improve utilization of crop diversification for weed management in northern European organic arable cropping systems. The overall goal is to maintain a diversified and manageable weed flora that can support beneficial organisms. The objective of this specific research conducted by the Group Crop Health of the University Rostock is to identify challenges in weed control, to investigate the role of crop diversification management for weed management in the field and to cluster weed species into groups according to susceptibility for crop diversity management. In order to reach this objective a diversity of methods are proposed. Data collection takes place on organic arable farms in five countries (Denmark, Sweden, Finland, Latvia and Germany) over the course of two years (2015-2016). Existing information and literature on weed occurrence and control challenges from all regions are compiled into an Ex-ante database and literature review. A two year on-farm weed survey is carried out in spring-sown cereals and combined with the collection of the field history with a focus on the implementation of crop diversification measures. All data is collected at the University of Rostock for processing and analysing; the weed survey data will be compared with the Ex-ante database and analysed for interactions with the crop diversification measures. Results will both be communicated towards the stakeholders, as well as serve for scientific publications.

The area cultivated with maize in Germany is continuously increasing throughout the last years. Nevertheless weeds in maize get small notice, probably since they are still easy to control. If maize cropping frequency and intensity continue to increase, problems with adapted weeds are likely to occur. To face these effects, it is worthwhile to know more about the appearance of typical maize weeds. In 2011 and 2012 a weed survey took place in four regions of Northern Germany. Weed species were identified and counted on 169 fields cropped with maize. Data about management of these fields was collected. One of the most wide spread weeds was Chenopodium album, which can also cause high yield losses. With a generalized linear mixed model five parameters were identified which influence the emergence of C. album: precipitation, cropping maize in the previous year, fertilizing with manure, soil organic matter and plant available phosphorous.

Increasing maize cultivation and changed cropping practices promote the selection of typical maize weeds that may also profit strongly from climate change. Predicting potential weed problems is of high interest for plant production. Within the project KLIFF, experiments were combined with species distribution modelling for this task in the region of Lower Saxony, Germany. For our study, we modelled ecological and damage niches of nine weed species that are significant and wide spread in maize cropping in a number of European countries. Species distribution models describe the ecological niche of a species, these are the environmental conditions under which a species can maintain a vital population. It is also possible to estimate a damage niche, i.e. the conditions under which a species causes damage in agricultural crops. For this, we combined occurrence data of European national data bases with high resolution climate, soil and land use data. Models were also projected to simulated climate conditions for the time horizon 2070 - 2100 in order to estimate climate change effects. Modelling results indicate favourable conditions for typical maize weed occurrence virtually all over the study region, but only a few species are important in maize cropping. This is in good accordance with the findings of an earlier maize weed monitoring. Reaction to changing climate conditions is species-specific, for some species neutral (E. crus-galli), other species may gain (Polygonum persicaria) or loose (Viola arvensis) large areas of suitable habitats. All species with damage potential under present conditions will remain important in maize cropping, some more species will gain regional importance (Calystegia sepium, Setara viridis).

Weeds in agriculture are controlled indirectly by strategic management tools (crop rotation, fertilization, tillage). Herbicide use is a direct tactical management tool for weed control. However, strategic and tactical measures interact together regarding weed management and thereby influence weed infestations and herbicide use. This study investigated the impact of strategic and tactical decisions in combination. It describes the development of a heuristic, which can be applied for different weed situations. By considering weed densities and species specific loss factors flexible herbicide decisions are derived for specific weed infestations and a given herbicide intensity. The implementation of decisions based on the heuristic is shown as an example for winter wheat crops in a rotation experiment at the study sites Rostock and Göttingen (Germany). The intensity of herbicide use serves for contrasts with three degrees (high, medium and low) representing three levels of target efficacy (100%, 85% and 60%). The introduced heuristic enables reproducible decisions for various weed infestations. First results show reduced herbicide use from high to the low level of herbicide intensity in terms of reduced numbers of active ingredients use.

In the past years, a large number of studies have examined various aspects of possible consequences of climate change for the biology and damage potential of arable weeds. However, there are merely a few examples that have comprehensively investigated individual weed species or arable crop systems within a clearly delimited geographical area. In the frame of the research co-operation KLIFF (Climate change impact and adaptation research for Lower Saxony), we tested an approach that combines a number of methods to span several scale levels and types of environmental factors, which was intended to provide as accurate as possible an estimate of the potential distribution and performance of individual arable weed species under the predicted future climate conditions. This approach was put to practice for the species Abutilon theophrasti, Amaranthus retroflexus, Echinochloa crus-galli, Datura stramonium, Iva xanthiifolia and Setaria viridis. We combined projections of the potential future distribution of the individual weed species based on a correlative distribution modelling approach (regional scale level) with pot experiments (local scale level) on the vegetative and generative performance of these species under climatic conditions predicted for the end of the current century for Lower Saxony. A synopsis revealed that the results obtained from the different approaches corresponded to a large extent. For A. retroflexus, D. stramonium, E. crus-galli, and S. viridis, both approaches indicated a neutral or positive effect of the predicted future climate on their potential distribution and performance, whereas the opposite was found for I. xanthiifolia. Merely for A. theophrasti, results of the two methods did not fully concur. Altogether, our results highlight that investigating climate change impact on weeds by combining several methods to span several scale levels allows fitting various data sets to a comprehensive picture for a delimited region. It has a number of strengths which may be augmented by the inclusion of further aspects. Therefore, this approach can be recommended for research of the regional impacts of climate change on arable weeds.

Herbicide decision support systems can calculate efficient, economically optimized herbicide mixtures with reduced dosages, if field specific weed data are given. Thus, they can be a sensible tool for integrated weed control. However, advises of decision support systems have to be tested before introducing them into practical farming. In Mecklenburg-Vorpommern two herbicide field trials were installed with four different prototypes of decision support systems. An untreated plot and three expert advices, private advisors, official advisory service and a farmer decision, were included as additional test variables. Herbicide efficacies in autumn, weed dry matter after spring applications, herbicide costs and wheat yield were measured to evaluate the decision support system prototypes. In one field trial with low weed density before treatments efficacies were at least 85%. In two prototypes efficacies were lower than in the expert plots. No significant differences between decision variables were found regarding weed dry matter after spraying in spring. On this site, herbicide costs were higher when expert advises were used compared to decision support system advises. No significant differences were detected in yield. Even yield in “untreated” was not significantly different. The second field trial carried higher weed densities. Here herbicide efficacies were lower in all treatments. Poa annua and Matricaria recutita were significantly affected by the treatments resulting from the decision tools. However, these differences did not result in statistically different weed dry matter or wheat yield. Three of the prototypes advised solutions with very low herbicide costs in autumn, but high costs in spring. As a result, total weed costs in these plots were higher than in the plots advised by experts. It is concluded from the field trials, that different prototypes of decision support systems are giving sensible herbicide advice. In fields with low weed density, reduction of herbicides costs seems possible.

To choose herbicides and their optimal dosages is a great challenge in chemical weed control in arable crops, because the choice of possible herbicide mixtures is big and economic consequences are hardly estimated. DSSHerbicide is a computer aided decision support system calculating cost-saving weed control measures. It is adapted to German conditions from the Danish Crop Protection Online system with German herbicide and weed data. To test the prototype of the system, fourteen herbicide trials were installed at conventional winter weed fields with differing weed densities in 2011 and 2012. Apart from the herbicide selection of DSSHerbicide recommendations from private advisers, official advisory service and farmers were implemented as test variables. The different ways of decision-making were investigated with the parameters chosen herbicides, herbicide costs, treatment frequency index, weeds left after treatments and wheat yield. Neither in herbicide costs, nor in treatment frequency index nor in yield significant differences between the decision support system on the one side and the expert advices on the other side were found. Biomass of weeds after treatments was significantly higher in the DSSHerbicide plots than in the plots of the official advisory service. In tendency, but not significantly, this led to higher yields in the plots of the official advisory service. Variation in herbicide costs and treatment frequency indices between the field trials was highest in the DSSHerbicide plots. A higher correlation of weed density before control and herbicide costs in the DSSHerbicide plots than in the expert plots indicates a field specific herbicide advice by the DSSHerbicide. The prototype worked with a limited number of implemented herbicides. Since herbicide advices of the decision support system were robust over the fourteen field trials, it will be worth implementing more herbicides in the system.

Several studies indicate links between regional occurrence of well adapted weed species and crop rotations. Monocultures or very short crop rotation, which increased in the past decades are crucial for the establishment and dispersion of problematic weed species. In this study the impact of crop rotation on the occurrence of the species Amaranthus retroflexus (L.), Anchusa arvensis (L.) M. Bieb., Echinochloa crus-galli (L.), Galium aparine (L.), Geranium pusillum (L.), Sisymbrium officinale (L.), Solanum nigrum (L.), Stellaria media (L.) Vill., Viola arvensis Murray is investigated in four crop rotations with varying potential of crop health risks. Therefore, maize (M), oilseed rape (WR) and winter wheat [early sowing (WWF) and late sowing (WWS)] are cropped in four different rotations (M, WR – WWF, WR – M – WWS and WR – WWF – M – WWS) at two study sites in Germany since year 2008 (Rostock) and 2009 (Göttingen). At the start of the project selected weed species were sown into some plots in order to simulate an artificial similar weed pressure. In all plots weed species densities were counted before spraying in a standardized observation method. Analyses of four, respectively three years give evidences of crop specific effects regarding A. arvensis, E. crus-galli, G. pusillum, S. nigrum and S. media. Moreover, first effects of crop rotations on problematic weed species indicates that expanding crop rotations is a preventive tool to reduce weed densities.

Velvetleaf, Abutilon theophrasti Medic., is an important arable weed worldwide. It is currently not present in the northern regions of Europe, but there are reasons why it may move northwards: The weed has not reached the northern edge of its climatic range, increasing temperatures, caused by climate change, will create more suitable growing conditions in northern areas, or the weed will adapt to cooler habitats. Velvetleaf has an indeterminate growth, meaning that the reproductive output largely depends on the length of the growing season, which is determined by the timing of emergence and seed production. The purposes of this preliminary study were:1) To evaluate the growth potential of A. theophrasti in the Northern German state of Mecklenburg-Vorpommern and2) to compare the phenology of populations from different European origins to evaluate the degree of adaptation to local climatic conditions.Forty 5 L pots were buried in the soil flush with the soil surface, 10 velvetleaf seeds of one of four populations from Spain, the Czech Republic, southern Germany or France were seeded in spring 2010 and subsequent emergence was recorded. In summer, plants were thinned to one seedling per pot and subsequent capsule production was recorded until the first frost.French and Spanish velvetleaf populations germinated earlier, produced capsules later, and tended to produce fewer capsules per plant than did populations from southern Germany or the Czech Republic. In addition, French and Spanish populations had a lower percentage of dormant seeds. These differences are in agreement with observations and predictions made for the northward expansion of velvetleaf in North America.Velvetleaf could grow and reproduce in northern Germany but further phenological changes, in particular a shorter growing season, a higher reproductive output and a higher level of physical dormancy, are to be expected as adaptations to local climatic conditions.

Data sets, comprising information on weed densities of 1103 maize fields in Germany as well as their crop management practices and site-specific characteristics, were analysed. The objectives were to describe the joint occurrence of weeds and to asses the influence of crop management on weed species composition.Per field, weed densities were assessed in ten, 0.1 m2 quadrats in young maize (2-6 leaves) before herbicide application. Fields were distributed all over Germany but the emphasis was on regions with high proportions of maize. Weed species composition was described with correspondence analysis and partial canonical correspondence analysis, using geographic location, climate, soil, and year as conditions. Tillage (mouldboard or chisel), crop rotation (proportion of maize and oilseed rape; maize as previous and/or pre-previous crop), maize density and whether or not manure was applied were added as independent crop management parameters. The net effects of these parameters were tested with a permutation test and were proved to be significant (p < 0.05).The relationship between weed density and herbicide use was analysed on a 200 field subset, involving 17 weed species. The potential herbicide use intensity was deduced from the efficacy data of advice papers. There was a significant relationship between the respective distance-matrices (rM = 0.21; p = 0.04). To visualize this relationship, separate correspondence analyses were conducted on weed incidence and theoretical herbicide effects, and a Procrustes analysis was performed. A Procrustes test indicated a correlation of 0.42 (p = 0.11) between weed assembly and herbicide use, which was characterized by the theoretical herbicide-weedefficacy. Consequently, in particular with crop rotations farmers seems to have a powerful tool to influence weed species composition.

Climate change will affect the agricultural ecosystem on different levels. It also alters interactions of weeds and crops. Each weed reacts on an individual basis to changes. Weeds can show an increase or decrease in abundance, can invade new areas or can completely vanish. They also can change traits to be more competitive. Overall, this will result in a different abundance and composition of weeds, as well as a different damaging potential. Land-use changes and agricultural adoption strategies to climate change will have dramatic influence on the interactions as well. Based on these interactions, there will be various options for dealing with climate change.

High intensity of oilseed rape (OSR) cropping and weeknesses in a restricted range of herbicides available for this crop favoured the spreading of problematic weeds in OSR during the last two decades.In a nationwide weed survey of OSR fields, the extent and composition of the weed infestation post herbicide application was determined. On the one hand the investigations aimed at identifying weed species that frequently occur despite herbicide application in OSR and are able to compete with the crop at late growth stages. On the other hand the survey was conducted to analyse the contribution of site properties and management factors to the spread of single problematic weed species. Between 2006 and 2008, a total of 452 fields were surveyed. At the end of OSR flowering the cover of each identified weed species was estimated across the whole field according to a five level scale. Additionally, information on site properties and management measures was collected. Median comparisons served to statistically verify preferences of Geranium pusillum, G. dissectum and G. rotundifolium regarding the investigated factors. By the use of classification and regression trees (CART), explanatory variables were weighted due to their importance to G. pusillum and G. dissectum and probabilities of occurrence due to different combinations of management factors and herbicide applications were calculated for these species.Geranium spp. were found in 46.5 % of the investigated OSR fields. All three species preferred sites with lower crop density and most frequently occurred in altitudes above 200 m and after multiple applications of herbicides that eliminated competing weeds. Furthermore the Geranium spp. showed different preferences regarding soil quality, the kind of soil tillage and the sowing date of OSR.

Whole plant bioassays are the most widely used test method for herbicide resistant grass weed populations. In whole plant bioassays, a susceptible standard population is usually included into the test procedure as the basis of resistance classification. Many institutions use their own susceptible standard in Apera spica-venti herbicide resistance tests. In contrast to Alopecurus myosuroides there are no approved susceptible or resistant standard populations. That is one reason why results of different institutions can hardly be compared with each other. We investigated three susceptible standard populations of Central European institutions. Dose response curves of three populations to iodosulfuron showed that two could be replaced by each other. A third population reacted with high variances between replications because of its heterogeneous origin from different fields and hence populations. Four more test populations emerged too poorly for establishing a bioassay. Further greenhouse investigations on emergence of four different populations were conducted. There was no difference in emergence between temperatures observed, but between populations. The rates of emergence varied between 4 % and 43 %. The rate of emergence and the mean time for emergence were positively correlated.

Crop protection services gather data on pesticides in the context of product registration and for region-specific extension. For this purpose, the region Hannover conducts field trials, which depending on the initiators can be based on different designs. The purpose of this study was to see if it is possible to extract additional data from these data sets by joint analysis. The 1076 data sets are based on 89 trials conducted in 40 locations in a radius of 50 km around the city of Hannover from 2003 to 2009. The region is situated in two ecoregional zones. There were area-specific differences in crop- and herbicide management. About half of the locations were chosen as trial location for herbicides only once and about 70 % of all treatments were tested only in one year. Consequently, possible year-effects remained hidden. Data with regard to the grass weeds, Alopecurus myosuroides (ALOMY) and Apera spica-venti (APESV), were particularly abundant. In 74 % of the trials, the density of ALOMY was > 200 ears per square meter. In contrast, in only 5 % of the trials was the density of APESV > 200 panicles per square meter. However, APESV will lead to higher yield losses than ALOMY at similar ear density. Furthermore, ALOMY predominantly occurred in locations that had the potential to produce higher crop yields than locations with APESV. Analyses of the timing of the surveys showed that crop yield could be best predicted based on weed surveys in early spring (R² = 0.54), whereas correlations with surveys conducted in autumn were weak (R² = 0.25). The results of this study show that the joint analysis of herbicide trials can yield valuable new insights. Joint analysis of herbicide efficiency over all trials could not be conducted due to lack of replication of trials with identical variants over time.

Introduction: Plant seeds from weeds and energy crops have the potential to survive anaerobic digestion (AD). Species able to form physically dormant, i.e., hardseeded (HS) seeds seem particularly resistant. However, it is not yet known to what extent the storage of the digestate after AD affects seed viability. Methods: Seed survival of five HS and six non-HS (NHS) species was investigated in three combinations of digestate storage (DS) and AD. First, untreated seeds were exposed to DS for maximum 12 weeks. To simulate short-circuited AD (ADshort) in biogas reactors, seeds were second subjected to lab-scale AD for 1 day before DS. Third, seeds of six species were exposed to full-scale AD (ADfull) followed by DS. Seed viability was determined using a combination of germination tests and tetrazolium staining. Viability was modeled as a function of exposure time. Results and discussion: Seed viability was affected by DS, AD and AD + DS, but responses varied greatly between species and treatments. With increasing exposure time, viability decreased after a lag-phase, remained stable or even increased. The NHS species Cichorium intybus , Daucus carota , Echium vulgare , and Verbascum thapsus were most susceptible, with seed-killing close to 100% if DS was involved. The HS species Malva sylvestris , Melilotus albus and Melilotus officinalis were most resistant. They survived all treatments and were alive after 35 days of ADfull plus 3 months of DS. The resistance potential of the HS species Abutilon theophrasti and Malva alcea and of the NHS species Chenopodium album and two tomato varieties was intermediate. None of them survived ADfull + DS, but except A. theophrasti they were viable after ADshort + DS. With few exceptions, seed-killing by AD + DS was higher than that by AD alone. In conclusion, DS and AD + DS have the potential to reduce seed viability, but do not completely inactivate all species. Therefore, digestate can be contaminated with viable seeds and may lead to the spread of weeds, especially after a short-circuited AD. In order to ensure the sustainable use of digestates in terms of weeds, we recommend to investigate the factors contributing to seed inactivation and the quantity of seed introduced to AD. [ABSTRACT FROM AUTHOR]