Kirsten Tørresen
Research Scientist
Abstract
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Authors
Aritz Royo-Esnal Andrea Onofri Alireza Taab Donato Loddo Jevgenija Necajeva Ahmet Uludag Agnieszka Synowiec Isabel M. Calha Lars Andersson Peter K. Jensen Ilhan Uremis Garifalia Economou Alistair J. Murdoch Kirsten TørresenAbstract
The variability in the emergence process of different populations was confirmed for two Echinochloa crus-galli populations, one from Italy (IT) and the second from Norway (NO). Seeds were sown in 12 localities over Europe and the Middle East, and the emergence patterns of IT and NO were compared with those of several local populations at each location. Seeds of each population were sown in pots buried to the ground level. The base temperature (Tb) for emergence was estimated by (1) analysing logistic models applied to the field emergence of IT and NO, and (2) a germination assay set in winter 2020 at constant temperatures (8, 11, 14, 17, 20, 26, 29°C) with newly collected seeds in 2019 from the same fields where IT and NO had previously been harvested in 2015. The logistic models developed for IT and NO in each location showed that the emergence pattern of IT was similar to that of the local populations in Poland, Italy, Spain, Turkey South and Iran, while NO fitted better to those in Sweden and Latvia. No germination was obtained for IT in a germination chamber, but the estimated Tb with the logistic model was 11.2°C. For NO, the estimated Tb was 8.8°C in the germination chamber and 8.1°C in the field. Results suggest that adaptation to local environmental conditions has led to inter-population differences in Tb and parameter estimates of thermal-time models to predict the emergence of E. crus-galli should only be used for populations with similar climatic and habitat conditions.
Authors
Aritz Royo-Esnal Andrea Onofri Donato Loddo Jevgenija Necajeva Peter K. Jensen Garifalia Economou Alireza Taab Agnieszka Synowiec Isabel M. Calha Lars Andersson Ahmet Uludag Ilhan Uremis Alistair J. Murdoch Kirsten TørresenAbstract
Echinochloa crus-galli (L.) P. Beauv. is one of the most important weeds. It is distributed worldwide and has adapted to diverse habitats and climatic conditions. This study aimed to compare the emergence patterns of two populations of E. crus-galli from different environments at 11 locations across Europe and the Middle East. Seeds of the two populations were collected from maize in Italy and from spring barley in Norway and were then buried in soil in autumn 2015. In the spring of 2016, the soil was disturbed around the usual seedbed preparation date in each location and emergence was recorded. The soil was again disturbed a year later and emergence was recorded for a second season. Total emergence, the times of onset, end and to 50% emergence and the period between 25% and 75% of emergence were analysed by two-way ANOVA and principal components analysis. The Italian population showed a higher emergence than the Norwegian population in Southern locations, while the ranking was reversed in Northern locations. In almost all locations, a tendency to emerge earlier was recorded for the Norwegian population, but the periods from 25% to 75% emergence were similar for both populations. Total emergence, and the times of onset and end of emergence seemed to be mainly under genotypic (plus maternal) control, suggesting there were different temperature thresholds for seedling emergence in each population. Conversely, the duration of emergence seemed to be mainly under environmental control. This research confirms the high variability between populations and suggests the need to continue identifying key characteristics for the development of efficient models for seedling emergence in specific climates and/or latitudes.
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VIPS is a technology platform for prognosis, monitoring and decision support for integrated pest management in crops in Norway. The service facilitates access to a Danish decision support tool, IPMwise, for the management of weeds. This tool, called VIPS-weeds in Norway, is adjusted to the Norwegian conditions for cereals. VIPS-weeds selects and adjusts the dose of herbicides according to weed species, weed density and temperature. The tool is being tested each year for local adaptations and updating. In 2021, four experiments were performed in spring wheat and barley. The experiments were designed in completely randomised blocks with three replications, and each included a control (unsprayed), a VIPS-weeds, and an adviser choice plot as well as plots for a variety of herbicides that are common in these crops. The weed species and density, development stage and possible herbicide resistance of each species in the control plots as well as crop information and temperature data were registered in VIPS-weeds three days before the normal spraying time. The suggested herbicides (set to be suggested based on the price) were applied to the VIPS-weeds plots. The effect of suggested herbicides and their dose was assessed as the reduction of weed coverage (%) in sprayed plots compared to the control plots 3-4 weeks after spraying. The average efficacy targets for the weed species (observed at least in two fields) Spergula arvensis, Viola sp., Stellaria media, Galeopsis sp., Chenopodium album, and Fumaria officinalis were predicted to be at 91, 84, 65, 83, 80, and 72% respectively, by VIPS-weeds. The results showed an average efficacy of 45, 58, 79, 80, 91 and 82% for these weeds, respectively. The VIPS-weeds solution was economically reasonable and gave similar results as adviser choice in terms of weed control and yield.
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Elymus repens (L.) Gould), Cirsium arvense (L.) Scop. and Sonchus arvensis L. are important arable creeping perennial weeds in Europe. These are clonal plants with subterranean reproductive organs (E. repens, rhizomes, the two dicots, horizontal creeping roots) sprouting from ramets. We tested the sprouting ability and early growth of ramet sprouts at temperatures typical for Nordic autumn climate and with different preconditions of the mother plant (time in autumn, mother plant age, climate change experiences of the mother plants (two experiments)). The species reacted differently, with S. arvensis not sprouting at all, and C. arvense ramets sprouting at higher temperatures than those of E. repens, which sprouted at all tested temperatures. Plant age affected only the ramet sprout biomass of E. repens. Climate change during mother plant growth only affected C. arvense, with the highest above-ground biomass of the sprouted ramets at an elevated temperature and ambient CO2. Testing earlier in autumn showed more sprouting and biomass for C. arvense and E. repens than testing later in the season. The observed temperature responses confirmed more and bigger sprouts with higher autumn temperatures. Controlling the sprouted ramets in autumn is easier for E. repens than for C. arvensis. Due to their low/no sprouting ability in autumn, the ramets of S. arvensis cannot be controlled in autumn.
Authors
Kirsten Tørresen Jukka Salonen Lars Olav Brandsæter Björn Ringselle Marian M. Weigel Eliyeh Ganji Bärbel GerowittAbstract
Book of Abstracts p. 213: The perennial creeping weeds Cirsium arvense (L.) Scop., Sonchus arvensis L. and Elymus repens (L.) Gould cause large problems in agricultural production in northern Europe. The management of these species is difficult in organic farming, but easier in conventional farming using herbicides. We collected and analysed literature on the response of these weed species to management practices in order to find knowledge gaps. C. arvense and E. repens are more studied compared to S. arvensis. Both C. arvense and E. repens have recently been the subjects of extended reviews. Elymus repens, a rhizomatous grass, is vulnerable to disturbance and competition due to weak seasonal dormancy, shallow creeping rhizomes and short-lived and low-spreading seeds. Tillage and mowing can effectively control E. repens, but efficacy varies between clones, seasons and treatment frequencies. Combined effects of direct control and competition from main crop/subsidiary crop merit further research. Cirsium arvense and S. arvensis are dicot species with creeping roots, with C. arvense roots being situated deeper in the soil than S. arvensis and both having deeper roots than the rhizomes of E. repens. Cirsium arvense can sprout from the intact root system even below the plough layer. Spring tillage has been shown to control C. arvense better than autumn tillage, and horizontal root cutter (prototype) have promising results on this species. Sonchus arvensis sprouts mainly in spring and summer thus indicating seasonal dormancy. Therefore, spring tillage controls S. arvensis better than autumn tillage. The effect of competition from main crop and subsidiary crops needs further investigation. While E. repens and C. arvense can be significantly controlled by a simple mechanical control strategy alone (repeated tillage and deep root disturbance, respectively), S. arvensis must be managed by a combination of different non-chemical methods. Identified gaps focus on the deep root system and sexual reproduction (C. arvense), the link between disturbance, competition, withering and dormancy in roots (S. arvensis), and the long-term effect of different integrated weed management strategies on the population dynamics (E. repens). We conclude that more research on all three species is needed, especially on the less studied S. arvensis. Keywords: Couch grass, creeping thistle, perennial sow-thistle, mechanical control, crop competition, cover crop, subsidiary crop Acknowledgements: This research was part of the project “AC/DC-weeds- Applying and Combining Disturbance and Competition for an agro-ecological management of creeping perennial weeds” funded within the ERA-Net Cofund SusCrop/EU Horizon 2020, Grant no. 771134.
Authors
Jevgenija Necajeva Aritz Royo-Esnal Donato Loddo Peter Jensen Alireza Taab Agnieszka Synowiec Ahmet Uludag Ilhan Uremis Alistair Murdoch Anna Bochenek Andrea Onofri Kirsten TørresenAbstract
Barnyard grass [Echinochloa crus-galli (L.) Beauv] is a competitive C4 weed species that is widely distributed throughout the world. Although it originated in warm climatic conditions, currently, it is found in Europe as far north as Norway. This study aimed to compare the phenological development of plants from different climatic conditions in varying environmental conditions. To represent the contrasting climatic conditions within Europe, seeds were collected in Norway and Italy, and distributed to the study participants, to be sown at 10 different sites as two common populations. In addition to that, seeds of two to three local populations were collected near each of the sites. The development of the plants was monitored in a pot experiment set up under field conditions. The time to reach heading in the first year of the experiment was 77.6% faster (ranging from 45.9 to 98.3% on average) in the Norwegian than in the Italian population. However, in the leaf development stage, the difference between the common populations was smaller by, 23.5% on average (0–46.7%) and was mostly not significant. Our results indicate that different E. crus-galli ecotypes, characterized by differences in their phenological development, evolved within the distribution area of this species in Europe. However, the early development of the plants progressed with negligible differences between populations. The findings reported here can be used to adapt existing models from one region to regions with different climatic conditions for use in decision support systems and for research into plant population dynamics.
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Reusing soil can reduce environmental impacts associated with obtaining natural fresh soil during road construction and analogous activities. However, the movement and reuse of soils can spread numerous plant diseases and pests, including propagules of weeds and invasive alien plant species. To avoid the spread of barnyardgrass in reused soil, its seeds must be killed before that soil is spread to new areas. We investigated the possibility of thermal control of barnyardgrass seeds using a prototype of a stationary soil steaming device. One Polish and four Norwegian seed populations were examined for thermal sensitivity. To mimic a natural range in seed moisture content, dried seeds were moistened for 0, 12, 24, or 48 h before steaming. To find effective soil temperatures and whether exposure duration is important, we tested target soil temperatures in the range 60 to 99 C at an exposure duration of 90 s (Experiment 1) and exposure durations of 30, 90, or 180 s with a target temperature of 99 C (Experiment 2). In a third experiment, we tested exposure durations of 90, 180, and 540 s at 99 C (Experiment 3). Obtaining target temperatures was challenging. For target temperatures of 60, 70, 80, and 99 C, the actual temperatures obtained were 59 to 69, 74 to 76, 77 to 83, and 94 to 99 C, respectively. After steaming treatments, seed germination was followed for 28 d in a greenhouse. Maximum soil temperature affected seed germination, but exposure duration did not. Seed premoistening was of influence but varied among temperatures and populations. The relationships between maximum soil temperature and seed germination were described by a common dose–response function. Seed germination was reduced by 50% when the maximum soil temperature reached 62 to 68 C and 90% at 76 to 86 C. For total weed control, 94 C was required in four populations, whereas 79 C was sufficient in one Norwegian population.
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Established invasive alien plant species make it difficult and costly to move and make use of infested soil in public and private construction work. Stationary soil steaming as a non-chemical control method has the potential to disinfect soil masses contaminated with seeds and other propagative plant materials. The outcome can vary depending on steaming temperature and duration. Higher temperatures and longer durations are relatively more efficient but may also have side-effects including change in soil physical and chemical characteristics. Barnyard grass (Echinochloa crus-galli) is among troublesome invasive species in Norway. We have tested different steam duration at 99°C to find the possible lowest effective exposure duration for killing seeds of this annual grass species. Four replications of 40 barnyard grass dry seeds of one population were placed in polypropylene-fleece bags (9*7 cm), moistened for 12 hours, and covered by the soil at a depth of 7 cm in 60*40*20 cm boxes. The boxes with soil and bags were steamed at 99°C for 1.5, 3 and 9 min. The bags including steamed seeds were taken out, opened, placed on soil surface in pots and covered by a thin layer of soil. The pots were placed in greenhouse and watered from below and seed germination was followed for a month. Moistened non-steamed seeds were used as control. It was shown that steaming at 99°C gave 0% germination indicating that 100% of the seeds were killed regardless of exposure duration while in the control seed germination was 100%. Consequently, to achieve an efficacy of 100%, exposure duration of 1.5 min would be enough. Finding the lowest possible steam temperature and exposure duration to get the highest possible seed killing in a seed mixture of different plant species as well as other factors to increase the heat transferability are under investigation. Keywords: Echinochloa crus-galli; Resource recovery; Steaming temperature and duration; Thermal soil disinfection
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Book of Abstracts p. 225: Perennial sow-thistle (Sonchus arvensis L.) is a problematic weed in arable crops in northern Europe. To control S. arvensis, strategies which reduce both seeds and creeping root production are essential. Inducing repeated sprouting should result in depleting root reserves and reduction in the subsequent shoot emergence. Earlier studies of S. arvensis in the northern European countries have shown a restricted sprouting ability from July/August/ September to October/November. To better understand the sprouting patterns, we conducted joint outdoor pot experiments from March 2020 until July 2021 in three northern European regions: Northern Germany, Norway, and Finland. In each pot, root pieces of 5 cm from local plant material were planted at 5cm depth. Above-ground plants were cut at the soil surface in the growing season of 2020 at 1) flower-bud stage, 2) first visible open flowers, 3) start of seed production, and 4) withering stage. Shoots were counted monthly in 2020 and 2021. In the year 2020, in Germany, sprouting, flowering, seed-set, and withering started earlier than at the other two sites. Significantly more shoots showed up at the flower-bud stage in Germany and Finland compared to Norway. In Finland, significantly more shoots were observed at the later cutting stages compared to the first counts at the flower bud stage. As a subsequent effect, fewest shoots showed up in 2021 at the German and Finnish sites after cutting at flower bud and early flowering stage. The lowest emerged shoot number in 2021 for Norway tended to occur after cutting at the flower bud stage and the start of seed production. Accordingly, cutting at the flower-bud stage decreases the ability to produce shoots in the next year. Keywords: Perennial sow-thistle, sprouting, cutting, shoots Acknowledgements: This research was part of the project “AC/DC-weeds” which is funded by ERA-Net Cofund SusCrop/EU Horizon 2020, Grant no. 771134
Authors
Bärbel Gerowitt Sabine Andert Lars Olav Brandsæter Jesper Rasmussen Marie-Helene Robin Jukka Salonen Kirsten Tørresen Han ZhangAbstract
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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Jukka Salonen Lars Olav Brandsæter Bärbel Gerowitt Jesper Rasmussen M-H. Robin Kirsten Tørresen Muriel Valantin-MorisonAbstract
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Han Zhang Sabine Andert Lars Olav Brandsæter Jesper Rasmussen M-H. Robin Jukka Salonen Kirsten Tørresen Muriel Valantin-Morison Bärbel GerowittAbstract
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Kirsten TørresenAbstract
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In autumn, agricultural perennial weeds prepare for winter and can store reserves into creeping roots or rhizomes. Little is known about influence of climate change in this period. We tested the effect of simulated climate change in autumn on three widespread and noxious perennial weeds, Elymus repens (L.) Gould, Cirsium arvense (L.) Scop. and Sonchus arvensis L. We divided and combined simulated climate change components into elevated CO2 concentration (525 ppm), elevated temperatures (+2–2.5°C), treatments in open‐top chambers. In addition, a control in the open‐top chamber without any increase in CO2 and temperature, and a field control outside the chambers were included. Two geographically different origins and three pre‐growth periods prior to the exposure to climate change factors were included for each species. All species increased leaf area under elevated temperature, close to doubling in E. repens and quadrupling in the dicot species. E. repens kept leaves green later in autumn. C. arvense did not benefit in below‐ground growth from more leaf area or leaf dry mass. S. arvensis had low levels of leaf area throughout the experiment and withered earlier than the two other species. Below‐ground plant parts of S. arvensis were significantly increased by elevated temperature. Except for root:shoot ratio of C. arvense, the effects of pure elevated CO2 were not significant for any variables compared to the open‐top chamber control. There was an additive, but no synergistic, effect of enhanced temperature and CO2. The length of pre‐growth period was highly important for autumn plant growth, while origin had minor effect. We conclude that the small transfer of enhanced above‐ground growth into below‐ground growth under climate change in autumn does not favour creeping perennial plants per se, but more leaf area may offer more plant biomass to be tackled by chemical or physical weed control.
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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Aritz Royo-Esnal Donato Loddo Jevgenija Necajeva Peter Kryger Jensen Friederike De Mol Garifalia Economou Alireza Taab Anna Bochenek Agnieszka Synowiec Isabel Calha Lars Andersson Ahmet Uludag Ilham Uremis Andrea Onofri Kirsten TørresenAbstract
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Jevgenija Necajeva Aritz Royo-Esnal Donato Loddo Peter Kryger Jensen Friederike De Mol Garifalia Economou Alireza Taab Anna Bochenek Agnieszka Synowiec Isabel Calha Lars Andersson Ahmet Uludag Ilham Uremis Kirsten TørresenAbstract
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Aritz Royo-Esnal Donato Loddo Jevgenija Necajeva Peter Kryger Jensen Friederike De Mol Garifalia Economou Alireza Taab Anna Bochenek Agnieszka Synowiec Isabel Calha Lars Andersson Ahmet Uludag Ilham Uremis Kirsten TørresenAbstract
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Marianne Stenrød Therese With Berge Ole Martin Eklo Alexander Melvold Engebretsen Andrea Ficke Valborg Kvakkestad Roar Lågbu Anne Prestvik Karen Refsgaard Divina Gracia P. Rodrigues Eivind Solbakken Jörn Strassemeyer Kirsten Tørresen Anne Falk ØgaardAbstract
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Kirsten Tørresen Jevgenija Necajeva J. Soukup Peter Kryger Jensen Friederike De Mol Garifalia Economou Alireza Taab S Babaei Anna Bochenek Agnieszka Synowiec E. Jakubiak Ahmet Uludag Alistair Murdoch Aritz Royo-EsnalAbstract
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Kirsten Tørresen Jevgenija Necajeva J. Soukup Friederike De Mol Garifalia Economou Alireza Taab S Babaei Anna Bochenek Agnieszka Synowiec E. Jakubiak Ahmet Uludag Alistair Murdoch Aritz Royo-EsnalAbstract
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Seed biology is important for emergence in the field and for future weed infestations. This chapter focuses on seed biology, germination, dormancy and efforts in predicting weed emergence from seeds from a European perspective. It presents a brief overview of population dynamics in time and space, the factors influencing the dynamics and how population dynamics can be modelled. Emergence from the seed-bank starts with germination, pre-emergence growth and finally emergence. In addition to seeds, vegetatively propagated material is briefly mentioned. Dormancy influences under what conditions that germination can occur and regulates timing of germination. Population dynamics are important for understanding the whole system and are often based on the life-cycle of weeds: seed-bank, seedlings, adult plants, seed production and dispersal. Challenges in modelling emergence and population dynamics are large, due to differences between and within populations of species, variability in species response and there being many weed species in the same field with contrasting characteristics.
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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Four field trials (spring wheat and oats) were conducted (one on clay soil, one on loam soil and two on silt soil) for three years in important cereal growing districts, to investigate the influence of tillage regimes (ploughing versus reduced tillage in either autumn or spring) and straw management (removed and retained) on plant residue amounts, weed populations, soil structural parameters and cereal yields. The effect of tillage on soil structure varied, mainly due to the short trial period. In general, the amount of small soil aggregates increased with tillage intensity. Reduced soil tillage, and in some cases spring ploughing, gave significantly higher aggregate stability than autumn ploughing, thus providing protection against erosion. However, decreasing tillage intensity increased the amounts of weeds, particularly of Poa annua on silt soil. Straw treatment only slightly affected yields, while effects of tillage varied between both year and location. Reduced tillage, compared to ploughing, gave only small yield differences on loam soil, while it was superior on clay soil and inferior on silt soil. Our results suggest that shallow spring ploughing is a good alternative to autumn ploughing, since it gave comparable yields, better protection against erosion and was nearly as effective against weeds.
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With the Directive 2009/128/EC on sustainable use of pesticides, reductions in herbicide use is a European target. The aim of this study was to compare the fi eld-specifi c herbicide use resulting from simulated integrated weed management (IWM) with farmer’s actual use. Two IWM tools applicable for cereals were explored: VIPS – a web-based decision support system, and DAT sensor – a precision farming technology for patch spraying. VIPS (adaptation of Danish “Crop Protection Online”) optimizes herbicide – and dose to weed species densityand growth stage (including ALS-herbicide resistant populations), temperature, expected yield, cereal species- and growth stage. Weeds were surveyed (0.25 m2, n=23-31) prior to post-emergence spraying in spring 2013 (six fi elds) and 2014 (eight fi elds). DAT sensor enables automatic patch spraying of annual weeds within cereals. It consists of an RGB camera and custom-made image analysis. DAT sensor acquired more than 900 images (0.06 m2) per fi eld. Threshold for simulated patch spraying was relative weed cover (weed cover/ total vegetation cover) = 0.042. Treatment frequency index (TFI, actual dose/maximum approved dose summed for all herbicides) was calculated. Without resistance strategy, average TFI for VIPS was higher for winter wheat (0.96) than for spring cereals (0.38). Spring cereal fi elds with resistance strategies gave an average TFI of 1.45. Corresponding TFI for farmer’s applications were 1.40, 0.90 and 1.26, respectively. For one fi eld wherein both tools were explored in 2013 and 2014, TFI values for VIPS were 1.86 and 1.50 due to resistant Stellaria media, while TFI for farmer’s sprayings were around 1.00. DAT sensor simulated herbicide savings of 69% and 99%, corresponding to TFI values of 0.58 and 0.01, respectively. As measured by TFI, DAT sensor showed a higher potential in herbicide savings than VIPS. VIPS is available without costs to end-users today, while DAT sensor represents a future tool.
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Marianne Stenrød Kirsten Tørresen Therese With Berge Andrea Ficke Ole Martin Eklo Anne Falk Øgaard Ola Flaten Karen Refsgaard Valborg KvakkestadAbstract
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Marianne Stenrød Kirsten Tørresen Therese With Berge Andrea Ficke Ole Martin Eklo Anne Falk Øgaard Ola Flaten Karen Refsgaard Valborg KvakkestadAbstract
In Europe there is an on-going process on implementing regulations aimed at reducing pollution from agricultural production systems, i.e. the Water Framework Directive and the Framework Directive for Sustainable Use of Pesticides. At the same time, there is an increasing focus on food security possibly leading to continued intensification of agricultural production with increased use of external inputs, such as pesticides and fertilizers. Application of sustainable production systems can only be achieved if they balance conflicting environmental and economic effects. In Norway, cereal production is of large importance for food security and reduction of soil and phosphorus losses, as well as pesticide use and leaching/runoff in the cereal production are of special concern. Therefore, we need to determine the most sustainable and effective strategies to reduce loss of top soil, phosphorus and pesticides while maintaining cereal yields. A three-year research project, STRAPP, is addressing these concerns. A catchment area dominated by cereal production is our common research arena within STRAPP. Since 1992 a database (JOVA) with data for soil erosion, nutrient and pesticide leaching/runoff (i.e. concentrations in stream water), yield, and agricultural management practices (fertilization, use of pesticides, soil tillage and rotations) has been established for this catchment allowing us to compare a unique diversity in cropping strategies in a defined location. An important part of STRAPP focuses on developing ‘best plant protection strategies’ for cereal fields in the study area, based on field inventories (manual and sensor based) of weeds and common diseases, available forecast systems, and pesticide leaching risk maps. The results of field studies during the growing seasons of 2013 and 2014 will be presented, with a focus on possible integrated pest management (IPM) strategies for weeds and fungal diseases in cereal production. We will also present the project concept and methods for coupling optimized plant protection strategies to (i) modelling of phosphorus and pesticide leaching/runoff, as well as soil loss, and (ii) farm-economic impacts and adaptations. Further, methods for balancing the conflicting environmental and economic effects of the above practices, and the evaluation of instruments for increased adoption of desirable management practices will be outlined.
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Kirsten TørresenAbstract
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Kirsten TørresenAbstract
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B.J. Schutte B.J. Tomasek A.S. Davis L. Andersson D.L. Benoit A. Cirujeda J. Dekker F. Forcella J.L. Gonzales-Andujar F. Graziani A.J. Murdoch P. Neve I.A. Rasmussen B. Sera J. Salonen F. Tei Kirsten Tørresen J. M. UrbanoAbstract
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Kirsten TørresenAbstract
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Marit Jørgensen Kirsten Tørresen Marit Dyrhaug Ingrid Myrstad Jan Svendsen Tone Magnussen Anniken Førde A. DiTommasoAbstract
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Marit Jørgensen Kirsten Tørresen M Dyrhaug I. Myrstad J. Svendsen T. Magnussen A. Førde A. DiTommasoAbstract
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Marit Jørgensen Kirsten Tørresen Marit Dyrhaug Ingrid Myrstad Jan Svendsen Tone Magnussen Anniken Førde A. DiTommasoAbstract
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Marianne Stenrød Kirsten Tørresen Ole Martin Eklo Anne Falk Øgaard Gudbrand Lien Karen Refsgaard Valborg KvakkestadAbstract
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P>Autumn growth of weeds (i) provides an opportunity for mechanical and chemical control in autumn and (ii) can be important for weed survival and infestation in the following spring. Growth characteristics of Elytrigia repens, Cirsium arvense and Sonchus arvensis in autumn were studied in 2004 and 2005, on plants of different origins and developmental stages (planted at various times from May to August). The plants were grown outdoors in large pots and were assessed during September and October each year. The study showed that (i) all species grew in autumn, but growth ceased and the species withered at different times; S. arvensis first, followed by C. arvense and then E. repens and (ii) less developed (i.e. younger) plants grew later in the autumn. This was demonstrated by leaf area development and biomass distribution during autumn. Older plants had a greater total biomass with relatively more rhizomes or creeping roots than younger plants. In young plants of C. arvense and S. arvensis, the biomass of creeping roots increased during autumn. The total biomass, however, changed little during autumn. These growth patterns indicate that E. repens will be the easiest, S. arvensis the most difficult and C. arvense in between, regarding control of these species in autumn.
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The control of Alopecurus geniculatus, Poa annua and Poa trivialis using iodosulfuron (Hussar/Hussar OD) was investigated in field experiments in the seed harvest year in timothy (Phleum pratense), and in the sowing year and seed harvest year in smooth meadow-grass (Poa pratensis) and red fescue (Festuca rubra). Iodosulfuron (10 g a.i. ha-1) usually had good effect on Poa trivialis and Alopecurus geniculatus. As for Poa annua the effect on seed contamination was better than on weed coverage in the field. Early application improved weed control in the seed harvest years, and iodosulfuron was shown to perform well at low temperatures. The herbicide often delayed timothy development, but caused seed yield reduction only in two out of eight experiments, both with moist soil at treatment. The visual damage increased with increasing rates and use of additives (alcoholetoxylate or rape oil). A questionnaire investigation among timothy growers in 2004 showed that farmers using Hussar had 43% lower contamination of P. trivialis in cleaned seed yield and 20% lower yield than the farmers not using Hussar. In some trials in timothy and smooth meadow-grass, the new formulation Hussar OD gave slightly more damage than the old formulation Hussar. While well-established timothy crops seem to tolerate some visual damage without seed yield reduction, the risk of yield reduction in first year crops can usually be avoided by splitting the application into 5 g a.i. ha-1 at 14 days intervals. In smooth meadow-grass and red fescue established without cover crop, repeated applications of 5 g a.i. ha-1 in the sowing year resulted in better control of P. annua and significant seed yield improvements compared to application only in the seed harvest year. Both Hussar and Hussar OD have off-label approvals for members of the Norwegian Seed Growers Association.
