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Cover cropping plays an important role in Integrated Weed Management (IWM). Weed suppression of cover crops occurs by competition, physical barrier on the soil and allelopathy. Under favourable growing conditions, cover crops can provide similar weed suppression in the autumn‐to‐spring period as repeated stubble tillage and non‐selective herbicides. The objective of this study was to test if cover crop species with higher allelopathic potential can suppress weeds in the field with less shoot biomass than cover crop species with lower allelopathic effects. Data of cover crop shoot biomass, percentage of weed suppression in the field and reduction of weed seed germination in petri‐dish bioassays treated with cover crop extracts were analysed from 11 experiments. Weed suppression in relation to cover crop biomass was better predicted by a Weibul three‐parameter model than with the Cousens model. Raphanus sativus var. oleiferus, Sinapis alba, Fagopyrum esculentum and Phacelia tanacetifolia needed at least three‐fold more biomass than Avena strigosa for 80% weed suppression. Vicia sativa had the lowest weed reduction of only 62%. Aqueous extracts of A. strigosa had the highest inhibiting effect on weed seed germination followed by R. sativus. The lowest effect was observed for P. tanacetifolia. It is assumed that for A. strigosa allelopathy strongly contributes to weed suppression whereas for P. tanacetifolia and other cover crops, competition plays the major role for weed suppression. The model can help growers and consultants to mix cover crop species for the autumn‐to‐spring period. Under dry conditions, species such as A. strigosa can provide high weed suppression with low biomass. Under moist conditions, rapidly growing cover crops such as S. alba suppress most weeds and deliver high biomass. [ABSTRACT FROM AUTHOR]

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

Pre-emergence herbicides in winter annual cereals often need to be combined with other weed control tactics to provide sufficient weed control efficacy for the entire growing season. In the present study, the new pre-emergence herbicide cinmethylin for the control of Alopecurus myosuroides Huds. in Europe was tested in four field experiments in winter wheat and winter triticale in Southwestern Germany over a period of three years. Treatments with cinmethylin were combined with stubble treatments and delayed drilling of winter annual cereals in a three-factorial block design. Average densities of A. myosuroides in the untreated control plots ranged from 38-1233 plants m-2. The pre-emergence herbicide Cinmethylin controlled 58-99% of A. myosuroides plants until 120 days after sowing. Additive and synergistic effects of cinmethylin and delayed drilling were found for all studies reducing A. myosuroides density by more than 90%. Stubble treatments including one and two passes of chisel ploughing, chisel ploughing followed by glyphosate application and conversation stubble tillage with a straw harrow did not result in significant different A. myosuroides densities in the following winter cereal crops. Winter wheat and winter triticale grain yields were significantly increased by cinmethylin and delayed drilling. These data underline the benefits of integrated weed management using different weed control tactics.

Durch die steigende Nachfrage nach nicht-chemischen Ansätzen zur Unkrautregulierung gewinnen mechanische Verfahren an Bedeutung. Für spätgesäte, konkurrenzschwache Kulturen wie Melisse (Melissa officinalis) wird empfohlen, mittels präventiver Bodenbearbeitung, etwa durch vorgezogene Saatbettbereitung („Falsches Saatbett“), Unkrautsamen im Boden wiederholt zur Keimung anzuregen und damit die Diasporenbank vor der Aussaat zu reduzieren. In einem zweifaktoriellen Versuch wurde der Zeitpunkt des Pflugeinsatzes (Herbst- oder Frühjahrsfurche) in Kombination mit vier Intensitäten einer flachen Frühjahrsbearbeitung mittels Kreiselegge herbologisch untersucht. Der Versuch wurde 2019/20 an einem ökologisch und einem konventionell bewirtschafteten Standort im Rheinland angelegt. Vor jedem Bodenbearbeitungsgang wurden Unkrautbonituren durchgeführt. Zusätzlich wurde die Diasporenbank im Oberboden (0-7 cm) an drei Terminen erfasst. Am ökologisch bewirtschafteten Standort war die Unkrautdichte drei Wochen nach Aussaat nach Herbstfurche in den drei- und vierfach gekreiselten Faktorkombinationen signifikant geringer im Vergleich zur Frühjahrsfurche (p = 0,023; p = 0,018). Arten mit leichtem Samengewicht (≤ 0,5 mg) wie Aphanes arvensis, Matricaria chamomilla, Papaver rhoeas, Veronica agrestis und Viola arvensis hatten in den viermal gekreiselten Varianten einen tendenziell höheren Anteil (41,1 % ± 23,6 %) im Vergleich zu einer einmaligen Saatbettbereitung (15,6 % ± 20,8 %). Diese wies tendenziell eine höhere Dichte an Arten mit höherem Samengewicht (> 1 mg) wie Ranunculus repens oder Chenopodium album auf (49,3 % ± 28,2 %). Dies lässt vermuten, dass die Keimung kleinerer Samen bei feineren Bodenaggregaten begünstigt wird. Am konventionell bewirtschafteten Standort wurden bei geringem Samenpotential im Oberboden (< 200 je m2) keine Effekte der Bodenbearbeitung auf Unkrautdichte und Artenzusammensetzung festgestellt. Die Ergebnisse des ersten Versuchsjahres zeigen, dass eine wiederholte flache Frühjahrsbearbeitung an einem Standort mit hohem Samenpotential (> 6000 Samen m-2) nicht zu einer Minderung der Unkrautdichte, jedoch zu einer Selektion eines bestimmten Artenspektrums führen kann.

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

Galinsoga quadriradiata and Galinsoga parviflora are very troublesome weeds in many organic vegetable crops in Europe. A very straightforward method to keep Galinsoga infestations under control is by targeting the Galinsoga seedbank. To identify cropping systems able to reduce the seedbank size in vegetable‐based cropping systems, the relationships between the seedbank size of Galinsoga species and prevailing soil/crop management practices and pedo‐hydrological conditions were investigated. Hereto, the seedbank of the 0–20 cm topsoil layer was sampled in 50 organic vegetable fields and analysed according to the seedling emergence method. Field history data were collected for the past 5 years, and physical, chemical and microbial soil quality was determined. Galinsoga quadriradiata was the most frequent and abundant Galinsoga species in the weed seedbank. The genus Galinsoga was present in 90% of the soil weed seedbanks of organic vegetable fields but displayed wide variation in abundance. Smallest Galinsoga seedbanks were found in fields that were predominantly tilled with non‐inversion implements or rotationally ploughed, and continuously cropped with competitive crops during the entire growing season (April 15‐November 15). Contrary to G. quadriradiata, seedbank size of G. parviflora was closely related to soil organic carbon content and sand fraction. Remarkably, soils with a low level of easily plant‐available phosphorus and concomitant high activity of arbuscular mycorrhizae had smaller G. quadriradiata seedbanks. To reduce Galinsoga infestations, fields should preferably be tilled without soil inversion, fertilised with organic amendments with low content of readily plant‐available phosphorus and cropped with competitive crops all season long. [ABSTRACT FROM AUTHOR]

This study presents an on-farm approach to investigate the impact of the sowing date on herbicide management in arable farming. Ten years of data (2012–2021) on the herbicide use and crop management practices of 4325 fields in north-eastern Germany were examined for winter barley, winter oilseed rape and winter wheat. We investigated whether the sowing date was related to the herbicide use intensity (described as Treatment Frequency Index, TFI) and mode of action (MoA) use (classified using the global HRAC classification). While the sowing of winter barley and winter oilseed rape took place over a short period of two weeks, sowing dates for winter wheat were spread over two months from the beginning of September to the end of October. Seventy-five percent of the winter barley fields were treated with HRAC group 2 herbicides and every second field was treated with herbicides in HRAC groups 15 and 3, respectively. Delayed autumn sowing of winter barley differing by 14 days decreased the in-crop use intensity of HRAC group 2 by up to 16%, for HRAC group 3 by up to 15% and for HRAC group 15 by up to 27%. In contrast, the herbicide management did not relate to the time of sowing in winter oilseed rape, except for HRAC groups 14 and 15. Ninety percent of the winter wheat fields were treated with HRAC group 2 herbicides and almost seventy-five percent with HRAC groups 15 herbicides, respectively. For winter wheat, our study provided evidence that delayed sowing dates in-mid October reduced the use intensity of HRAC group 2 by up to 41% and for HRAC 15 by up to 35%, respectively, compared with sowing at the beginning of September. With regard to the European-wide efforts to reduce chemical pesticide use by 50% by 2030, we conclude that cultural weed control with a sowing date delay may be highly effective at meeting this requirement. Additionally, delayed sowing dates have the potential to reduce the use intensity of MoA with a high resistance risk. • Delayed sowing is negatively related to the in-crop herbicide use intensity. • Delayed sowing of winter barley decreased the in-crop use of HRAC group 2/3/15. • For winter wheat, delayed sowing reduced HRAC 2 by up to 41% and for HRAC 15 by up to 35%. • Delayed sowing has the potential to reduce the MoA with a high resistance risk. [ABSTRACT FROM AUTHOR]

Summary: Biofumigation may be a promising tool for depletion of persistent weed seedbanks/bud banks. This technique is based on the incorporation of chopped glucosinolate‐rich plant biomass into the soil, upon which isothiocyanates with herbicidal properties are released. To gain acceptance by farmers and foster its implementation, the biofumigation process should be further optimised. This study elucidated the impact of biological (species), technical (burial depth, ground cover) and pedohydrological (temperature and moisture content) factors on efficacy of Brassica juncea biofumigation under (semi‐)natural conditions. In a first experiment (field experiment), seeds and vegetative propagules of various weed species were buried at different depths and exposed to different doses of fresh fine‐chopped B. juncea biomass in the presence or absence of a plastic ground cover. In a second experiment (container experiment), buried seeds of ten species were subjected to biofumigation at diverging soil organic matter content, soil moisture content and soil temperature. In a third experiment (dose–response Petri dish bioassay), unburied seeds of eight species were subjected to various doses of rehydrated B. juncea powder. Biofumigation efficacy was determined by analysing viability of treated and untreated propagules. In general, efficacy of biofumigation increased with decreasing burial depth and increasing B. juncea dose. Biofumigation was highly effective (mortality >85%) against small‐seeded species but less effective (mortality 0%–20%) against hard‐seeded and large‐seeded species at 200 t ha−1. Vegetative propagules of Sonchus arvensis, Equisetum arvense and Convolvulus sepium were highly sensitive (mortality >90%) to biofumigation. Efficacy was most pronounced under moist warm incubation conditions, in the presence of a plastic ground cover. [ABSTRACT FROM AUTHOR]

Current awareness about the environmental impact of intensive agriculture, mainly pesticides and herbicides, has driven the research community and the government institutions to program and develop new eco-friendly agronomic practices for pest control. In this scenario, integrated pest management and integrated weed management (IWM) have become mandatory. Weeds are commonly recognized as the most important biotic factor affecting crop production, especially in organic farming and low-input agriculture. In herbaceous field crops, comprising a wide diversity of plant species playing a significant economic importance, a compendium of the specific IWM systems is missing, that, on the contrary, have been developed for single species. The main goal of this review is to fill such gap by discussing the general principles and basic aspects of IWM to develop the most appropriate strategy for herbaceous field crops. In particular, a 4-step approach is proposed: (i) prevention, based on the management of the soil seedbank and the improvement of the crop competitiveness against weeds, (ii) weed mapping, aiming at knowing the biological and ecological characteristics of weeds present in the field, (iii) the decision-making process on the basis of the critical period of weed control and weed thresholds and iv) direct control (mechanical, physical, biological and chemical). Moreover, the last paragraph discusses and suggests possible integrations of allelopathic mechanisms in IWM systems.

Alopecurus myosuroides Huds. has become one of the most abundant grass weeds in Europe. High percentages of winter-annual crops in the rotation, earlier sowing of winter wheat and non-inversion tillage favor A.myosuroides. Additionally, many populations in Europe have developed resistance to acetyl-CoA carboxylase (ACCase), acetolactate synthase (ALS) and photosynthetic (PSII) inhibitors. Hence, yield losses due to A.myosuroides have increased. On-farm studies have been carried out in Southern Germany over five years to investigate abundance, control efficacies and crop yield losses due to A.myosuroides. Three crop rotations were established with varying proportions of winter- and summer-annual crops. The crop rotations had a share of 0, 25 and 50% of summer-annual crops. Within each crop rotation, three herbicide strategies were tested. In contrast to classical herbicidal mixtures and sequences, the aim of one of the herbicide strategies was to keep selection pressure as low as possible by using each mode of action (MOA) only once during the five years. A.myosuroides population was susceptible to all herbicide at the beginning of the experiment. Initial average density was 14 plants m−2. In the rotation with only winter-annual crops, density increased to 5347 ears m−2 in the untreated control plots. Densities were lower in the rotations with 25% and even lower with 50% summer-annual crops. Control efficacies against A. myosuroides in the herbicide strategy using only MOAs of the HRAC-groups B and A, according to the Herbicide Resistance Action Committee (HRAC) classification on MOA, dropped after five years compared to the strategy of changing MOA in every year. Nevertheless, the results demonstrate the need for combining preventive and direct weed-management strategies to suppress A.myosuroides and maintain high weed-control efficacies of the herbicides.

Current awareness about the environmental impact of intensive agriculture, mainly pesticides and herbicides, has driven the research community and the government institutions to program and develop new eco-friendly agronomic practices for pest control. In this scenario, integrated pest management and integrated weed management (IWM) have become mandatory. Weeds are commonly recognized as the most important biotic factor affecting crop production, especially in organic farming and low-input agriculture. In herbaceous field crops, comprising a wide diversity of plant species playing a significant economic importance, a compendium of the specific IWM systems is missing, that, on the contrary, have been developed for single species. The main goal of this review is to fill such gap by discussing the general principles and basic aspects of IWM to develop the most appropriate strategy for herbaceous field crops. In particular, a 4-step approach is proposed: (i) prevention, based on the management of the soil seedbank and the improvement of the crop competitiveness against weeds, (ii) weed mapping, aiming at knowing the biological and ecological characteristics of weeds present in the field, (iii) the decision-making process on the basis of the critical period of weed control and weed thresholds and iv) direct control (mechanical, physical, biological and chemical). Moreover, the last paragraph discusses and suggests possible integrations of allelopathic mechanisms in IWM systems. [ABSTRACT FROM AUTHOR]

Alopecurus myosuroides Huds. has become one of the most abundant grass weeds in Europe. High percentages of winter-annual crops in the rotation, earlier sowing of winter wheat and non-inversion tillage favor A.myosuroides. Additionally, many populations in Europe have developed resistance to acetyl-CoA carboxylase (ACCase), acetolactate synthase (ALS) and photosynthetic (PSII) inhibitors. Hence, yield losses due to A.myosuroides have increased. On-farm studies have been carried out in Southern Germany over five years to investigate abundance, control efficacies and crop yield losses due to A.myosuroides. Three crop rotations were established with varying proportions of winter- and summer-annual crops. The crop rotations had a share of 0, 25 and 50% of summer-annual crops. Within each crop rotation, three herbicide strategies were tested. In contrast to classical herbicidal mixtures and sequences, the aim of one of the herbicide strategies was to keep selection pressure as low as possible by using each mode of action (MOA) only once during the five years. A.myosuroides population was susceptible to all herbicide at the beginning of the experiment. Initial average density was 14 plants m−2. In the rotation with only winter-annual crops, density increased to 5347 ears m−2 in the untreated control plots. Densities were lower in the rotations with 25% and even lower with 50% summer-annual crops. Control efficacies against A. myosuroides in the herbicide strategy using only MOAs of the HRAC-groups B and A, according to the Herbicide Resistance Action Committee (HRAC) classification on MOA, dropped after five years compared to the strategy of changing MOA in every year. Nevertheless, the results demonstrate the need for combining preventive and direct weed-management strategies to suppress A.myosuroides and maintain high weed-control efficacies of the herbicides. [ABSTRACT FROM AUTHOR]