Biografi

Jeg begynte på NIBIO i 2017 med ansvar for forskning om ugras i grasmark, frøeng, frukt, bær og grønne urbane områder (inkl. golf), samt plantevernresistens hos ugras. Nylig fikk jeg også ansvar for rådgivningsverktøyet VIPS-ugras.  

Jeg gikk biologi-geologi programmet på Stockholms Universitet 2006-2010 og tog min PhD ved Sveriges Landbruksuniversitet (SLU) 2011-2015. Fra min PhD og postdoc har jeg mye erfarenhet av ikke-kjemisk kontroll av flerårige ugras, spesielt kveke (Elymus repens).  

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Docks (Rumex spp.) are a considerable problem in grassland production worldwide. We investigated how different cultural management techniques affected dock populations during grassland renewal: (I) renewal time, (II) companion crop, (III) false seedbed, (IV) taproot cutting (V), plough skimmer and (VI) ploughing depth. Three factorial split-split plot experiments were carried out in Norway in 2007–2008 (three locations), 2008–2009 (one location) and 2009 (one location). After grassland renewal, more dock plants emerged from seeds than from roots. Summer renewal resulted in more dock seed and root plants than spring renewal. Adding a spring barley companion crop to the grassland crop often reduced dock density and biomass. A false seedbed resulted in 71% fewer dock seed plants following summer renewal, but tended to increase the number of dock plants after spring renewal. In some instances, taproot cutting resulted in less dock biomass, but the effect was weak and inconsistent, and if ploughing was shallow (16 cm) or omitted, it instead increased dock root plant emergence. Fewer root plants emerged after deep ploughing (24 cm) compared to shallow ploughing, and a plough skimmer tended to reduce the number further. We conclude that a competitive companion crop can assist in controlling both dock seed and root plants, but it is more important that the renewal time is favourable to the main crop. Taproot cutting in conjunction with ploughing is not an effective way to reduce dock root plants, but ploughing is more effective if it is deep and a skimmer is used.

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Tillage controls perennial weeds, such as Elymus repens, partly because it fragments their underground storage organs. However, tillage is difficult to combine with a growing crop, which limits its application. The aim of this study was to evaluate how soil vertical cutting with minimum soil disturbance and mowing affect the growth and competitive ability of E. repens in a grass–clover crop. A tractor-drawn prototype with vertical disks was used to fragment E. repens rhizomes with minimal soil and crop disturbance. In experiments performed in 2014 and 2015 at a field site close to Uppsala, Sweden, the rhizomes were fragmented before crop sowing (ERF), during crop growth (LRF), or both (ERFCLRF). Fragmentation was combined with repeated mowing (yes/no) and four companion crop treatments (none, Italian ryegrass, white clover, and grass/clover mixture). The results showed that in the grass–clover crop, rhizome fragmentation reduced E. repens rhizome biomass production and increased Italian ryegrass shoot biomass. ERF and LRF both reduced E. repens rhizome biomass by about 38% compared with the control, while ERFCLRF reduced it by 63%. Italian ryegrass shoot biomass was increased by 78% by ERF, 170% by LRF and 200% by ERFCLRF. Repeated mowing throughout the experiment reduced E. repens rhizome biomass by about 75%. Combining repeated mowing with rhizome fragmentation did not significantly increase the control effect compared to mowing alone. We concluded that rhizome fragmentation using vertical disks can be used both before sowing and during crop growth to enhance the controlling effect of grass–clover crops on E. repens.

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For å følge opp mistanke om og tidligere påvisninger av plantevernmiddelresistens, ble følsomheten for plantevernmidler undersøkt i 2018 hos: (1) glansbiller i seks felt med oljevekster i Akershus og Østfold, (2) veksthuspinnmidd i to jordbærfelt i Hedmark og Vest-Agder og tre bringebærtunneler i Vest-Agder og Sogn og Fjordane, (3) gråskimmel fra seks eplehager i Buskerud og Hordaland, (4) stivdylle i en kornåker i Akershus og (5) linbendel i to kornåkre i Akershus og Trøndelag. Tre av fem glansbillepopulasjoner var moderat resistente eller resistente mot Karate (lambda-cyhalothrin), fire av seks populasjoner var moderat resistente mot Mavrik (tau-fluvalinat), og tre av fire populasjoner hadde nedsatt følsomhet for Biscaya (tiakloprid). Ingen av glansbillepopulasjonene var resistente mot Avaunt (indoksakarb). Vi fant indikasjoner på at veksthusspinnmidd fra jordbær og bringebær kan være i ferd med å utvikle resistens mot Envidor (spirodiklofen), Floramite (bifenazat) og Danitron (fenpyroksimat). Med enkelte unntak ble det ikke påvist alvorlig grad av resistens hos veksthusspinnmidden, men undersøkelsen har vært av begrenset omfang, og bør utvides. Ingen av veksthusspinnmidd-populasjonene var resistente mot Vertimec (abamektin). Hos gråskimmel fra eple ble moderat resistens og resistens mot Topsin (tiofanatmetyl) påvist hos nesten halvparten av de 44 isolatene som ble testet, mens 18 % av 56 isolater var resistente mot Teldor (fenheksamid), og mellom 12 og 8 % var moderat resistente og/ eller resistente mot Scala (pyrimetanil), boskalid, Comet (pyraklostrobin) og Rovral (iprodion). Multiresistens ble funnet hos 15 % av isolatene. Det ble ikke funnet resistens mot fludioksinil. Det ble påvist resistens mot ALS-hemmerne Express (tribenuronmetyl) og Hussar OD (jodsulfuron-metyl-natrium) hos stivdylle i kornåkeren i Akershus, og mot Express, Hussar OD og Primus (florasulam) hos linbendel i kornåkrene i både Akershus og Trøndelag.

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Glyfosat er det mest brukte plantevernmidlet i Norge og på verdensbasis. Det har i de siste årene vært diskutert om dette ugrasmiddelet skulle få fornyet godkjenning. I 2017 ble glyfosat godkjent for fem nye år til 2022. Dersom glyfosat fases ut er en redd det vil få store negative konsekvenser for jordbruk og matproduksjon. Glyfosat brukes til å bekjempe ugras og andre uønska planter på dyrka og udyrka arealer. I jordbruket er glyfosat spesielt viktig for å begrense ugrasets avlingsreduserende effekt. I norsk jordbruk brukes glyfosat hovedsakelig til å bekjempe ugrasarten kveke i korndominerte omløp og ved fornying av grasmark. Ved redusert jordarbeiding er glyfosat viktig for bekjemping av flerårige og andre overvintrende ugras. Vi har i denne rapporten kartlagt kunnskap relevante for norske forhold på hvilke ikke-kjemiske og kjemiske alternativer til glyfosat som en har/kan få i framtida i korn og grasmark slik at matproduksjonen kan opprettholdes. Mekaniske tiltak som pløying og ulike former for jordarbeiding i stubben mot kveke og andre ugras, og radrensing i korn mot ugras generelt er viktige alternativer til glyfosat. Det er også noen nye redskapstyper (rotskjærere) som virker lovende i bekjemping av ugras. Videre så vil en god jord- og plantekultur med et godt vekstskifte bidra til å holde ugraset under kontroll. Per i dag fins det noen få kjemiske alternativer mot kveke i hvete, rughvete og rug og mot tofrøblada rotugras i korn. Det er andre kjemiske alternativer som kan undersøkes mer for bruk i stubbåker/til brakking av grasmark som for eksempel ulike organiske syrer og grasugrasmidler for tofrøblada kulturer........

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Docks (Rumex spp.) are a considerable problem in grassland production worldwide. We investigated how different cultural management techniques affected dock populations during grassland renewal: (I) renewal time, (II) companion crop, (III) false seedbed, (IV) taproot cutting (V), plough skimmer and (VI) ploughing depth. Three factorial split-split plot experiments were carried out in Norway in 2007–2008 (three locations), 2008–2009 (one location) and 2009 (one location). After grassland renewal, more dock plants emerged from seeds than from roots. Summer renewal resulted in more dock seed and root plants than spring renewal. Adding a spring barley companion crop to the grassland crop often reduced dock density and biomass. A false seedbed resulted in 71% fewer dock seed plants following summer renewal, but tended to increase the number of dock plants after spring renewal. In some instances, taproot cutting resulted in less dock biomass, but the effect was weak and inconsistent, and if ploughing was shallow (16 cm) or omitted, it instead increased dock root plant emergence. Fewer root plants emerged after deep ploughing (24 cm) compared to shallow ploughing, and a plough skimmer tended to reduce the number further. We conclude that a competitive companion crop can assist in controlling both dock seed and root plants, but it is more important that the renewal time is favourable to the main crop. Taproot cutting in conjunction with ploughing is not an effective way to reduce dock root plants, but ploughing is more effective if it is deep and a skimmer is used.

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Tillage controls perennial weeds, such as Elymus repens, partly because it fragments their underground storage organs. However, tillage is difficult to combine with a growing crop, which limits its application. The aim of this study was to evaluate how soil vertical cutting with minimum soil disturbance and mowing affect the growth and competitive ability of E. repens in a grass–clover crop. A tractor-drawn prototype with vertical disks was used to fragment E. repens rhizomes with minimal soil and crop disturbance. In experiments performed in 2014 and 2015 at a field site close to Uppsala, Sweden, the rhizomes were fragmented before crop sowing (ERF), during crop growth (LRF), or both (ERFCLRF). Fragmentation was combined with repeated mowing (yes/no) and four companion crop treatments (none, Italian ryegrass, white clover, and grass/clover mixture). The results showed that in the grass–clover crop, rhizome fragmentation reduced E. repens rhizome biomass production and increased Italian ryegrass shoot biomass. ERF and LRF both reduced E. repens rhizome biomass by about 38% compared with the control, while ERFCLRF reduced it by 63%. Italian ryegrass shoot biomass was increased by 78% by ERF, 170% by LRF and 200% by ERFCLRF. Repeated mowing throughout the experiment reduced E. repens rhizome biomass by about 75%. Combining repeated mowing with rhizome fragmentation did not significantly increase the control effect compared to mowing alone. We concluded that rhizome fragmentation using vertical disks can be used both before sowing and during crop growth to enhance the controlling effect of grass–clover crops on E. repens.

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Quackgrass is a problematic agricultural weed in the temperate zones of the world and is difficult to control without herbicides or intensive tillage. However, it may be possible to control quackgrass with less environmental impact by combining multiple low-intensity control methods. A pot experiment was conducted in July to October 2012 and repeated in June to September 2013 to investigate the effect of rhizome fragmentation, competition from white clover, shoot-cutting frequency, and cutting height on quackgrass. Rhizome fragmentation was expected to result in more, but weaker, quackgrass shoots that would be more vulnerable to shoot cutting and competition. However, by 20 d past planting, rhizome fragmentation did not change the total number of quackgrass shoots per pot, because an increase in main shoots was offset by a decrease in tiller numbers. Rhizome fragmentation did not reduce quackgrass biomass acquisition during the experimental period. Although rhizome fragmentation did reduce total fructan content, it did not enhance the effect of clover competition, shoot-cutting frequency, or shoot-cutting height. Clover competition by itself reduced quackgrass shoot numbers by 72%, rhizome biomass by 81%, and belowground fructan concentration by 10 percentage points, compared with no competition. The more frequently quackgrass shoots were cut, the less biomass quackgrass acquired, and a high shoot-cutting frequency (each time quackgrass reached 2 leaves) resulted in a lower belowground fructan concentration than a low shoot-cutting frequency (at 8 leaves). However, in pots without competition, a higher shoot-cutting frequency resulted in more quackgrass shoots. A lower shoot-cutting height (25 mm) had more impact when shoot cutting was more frequent. In conclusion, rhizome fragmentation did not reduce the number of quackgrass shoots or rhizome biomass, but competition from white clover, a high shoot-cutting frequency, and a low shoot-cutting height strongly suppressed quackgrass biomass and fructan acquisition.

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Background and Aims Competitive crops are a central component of resource-efficient weed control, especially for problematic perennial weeds such as Elymus repens. Competition not only reduces total weed biomass, but denial of resources can also change the allocation pattern – potentially away from the underground storage organs that make perennial weeds difficult to control. Thus, the competition mode of crops may be an important component in the design of resource-efficient cropping systems. Our aim was to determine how competition from companion crops with different modes of competition affect E. repens biomass acquisition and allocation and discuss that in relation to how E. repens responds to different levels of light and nutrient supply. Methods Greenhouse experiments were conducted with E. repens growing in interspecific competition with increasing density of perennial ryegrass or red clover, or growing at three levels of both light and nutrient supply. Key ResultsElymus repens total biomass decreased with increasing biomass of the companion crop and the rate of decrease was higher with red clover than with perennial ryegrass, particularly for E. repens rhizome biomass. A reduced nutrient supply shifted E. repens allocation towards below-ground biomass while a reduced light supply shifted it towards shoot biomass. Red clover caused no change in E. repens allocation pattern, while ryegrass mostly shifted the allocation towards below-ground biomass, but the change was not correlated with ryegrass biomass. Conclusions The companion crop mode of competition influences both the suppression rate of E. repens biomass acquisition and the likelihood of shifts in E. repens biomass allocation.

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Det er per i dag påvist resistens eller nedsatt følsomhet mot kjemiske plantevernmidler hos flere skadedyr, plantepatogener og ugras i norske jord- og hagebrukskulturer. Hos skadedyr er resistens mot pyretroider og nedsatt følsomhet for tiakloprid vanlig hos rapsglansbille i oljevekster. Resistens mot pyretroider er påvist hos ferskenbladlus og potetsikade fra potet, gulrotsuger fra gulrot, ferskenbladlus fra persille, kålmøll og ferskenbladlus fra kålvekster, jordbærsnutebille fra jordbær, og ferskenbladlus, bomullsmellus, veksthusmellus og sør-amerikansk minerflue fra veksthus. Det er også funnet resistens mot pirimikarb hos ferskenbladlus og nedsatt følsomhet for imidakloprid hos ferskenbladlus og bomullsmellus. I jordbær og bringebær er det indikasjoner på begynnende resistensutvikling mot flere av middmidlene. Hos plantepatogener er resistens mot QoI-fungicider påvist hos gråskimmel fra jordbær, bringebær og gran i skogplanteskoler, hos mjøldoggsopper i jordbær og veksthusagurk, og hos bladflekksopper i hvete. Resistens mot triazoler er funnet i flere bladflekksopper i hvete. Resistens mot hydroksyanilid- og SDHI-er utbredt hos gråskimmel fra jordbær og bringebær, og i skogplanteskoler er det påvist resistens mot tiofanater.....

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Without herbicides, the control of Elymus repens relies on intensive tillage, often in the form of repeated post-harvest stubble cultivations followed by ploughing. This is costly and time-consuming and also increases the risk of nitrogen leaching. Our aim was to quantify the controlling effect on E. repens of single and repeated cultivation and differing time of cultivation in relation to spring cereal harvest. A 2-year experiment was conducted at two sites in the south and east of Sweden in 2011–2012 and 2012–2013. We compared no, single and repeated tine cultivation followed by mouldboard ploughing; the single cultivation was performed directly after harvest or 20 days after harvest; when repeated, the first cultivation was performed immediately or 5 days after harvest, followed by a second cultivation 20 days after harvest. Tine cultivation in combination with mouldboard ploughing resulted in 50–70% lower rhizome biomass, and increased average subsequent cereal yields by 0–130% compared with ploughing alone. Large E. repens populations appeared to be more efficiently reduced by tine cultivation than smaller populations. A single tine cultivation 20 days after harvest tended to result in a higher E. repens shoot density and more rhizome biomass in the subsequent year than tine cultivation directly after harvest. Additional cultivation 20 days after harvest did not improve control of E. repens or the subsequent cereal grain yield, compared with a single cultivation conducted directly after harvest. In conclusion, preventing the growth of E. repens during the early part of the post-harvest autumn period was more important than starving rhizomes with repeated cultivations.

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Methods for control of couch grass (Elymus repens L.) with reduced tillage and cover crops to achieve low risk of nitrogen (N) and phosphorus (P) leaching were investigated. Treatments with reduced post-harvest tillage (one or two passes with duckfoot cultivator), hoeing between rows in combination with a cover crop, and a cover crop mown twice during autumn were compared with treatments with conventional disc cultivation and the control without tillage or cover crop. The study was conducted on a sandy soil in Sweden with measurements of N and P leaching. A 2-year experimental protocol was used, repeated twice. Treatments were implemented in the first year, and effects on couch grass (shoot density, shoot and rhizome biomass) were measured during autumn and in the second year. Significant effects of a single duckfoot cultivation and cover crop strategies were observed on couch grass shoot density in autumn but persistent effects were not verified. In conclusion, a single cultivation after harvest instead of repeated reduced the risk of N leaching and a cover crop in combination with hoeing or mowing effectively reduced it. Repeated cultivations resulted in mean annual N leaching of 26 kg N ha−1 compared with 20 kg in the treatment with one cultivation, 17 kg in the control, 16 and 12 kg in cover crop treatments with mowing and hoeing, respectively. The P leaching was small (0.04–0.09 P ha−1 year−1), but there were indications of increased P drainage water concentrations in the treatment with a cover crop which was mown.

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Elymus repens is a perennial grass weed that causes great yield losses in a variety of crops in the southern and northern temperate zones. Primary control methods for E. repens are herbicides or intensive tillage, both of which have a number of negative side-effects, e.g. herbicides can contaminate groundwater, and tillage can cause increased nitrogen leaching. The aim of this thesis was to investigate how to make non- herbicide control of Elymus repens more resource efficient in terms of less energy demanding soil cultivation and reduced nitrogen leaching. Three field experiments were used to test cover crop competition, mowing and different types of optimised tillage techniques and timing, as well as the combination of under-sown cover crops and mowing or row hoeing. The growth, biomass allocation and morphological responses of E. repens to competition were studied in a greenhouse experiment. The effect of competition from under-sown cover crops on E. repens seems to depend greatly on the cover crop biomass achieved. At high biomass levels, the cover crop can be highly suppressive (Paper IV) and reduce nitrogen leaching (Paper III), while at low levels they can still provide benefits such as reduced E. repens shoot biomass and increased subsequent cereal yield (Paper I). However, a low-yielding red clover cover crop increased E. repens rhizome production by 20-30%. Under-sown cover crops were successfully combined with both mowing and row hoeing (Paper I & III), but while repeated mowing reduced E. repens rhizome production by 35% it could not be shown to give a competitive advantage to the cover crops over E. repens (Paper I). However, the low nitrogen leaching and reduced downward transport of nitrogen when mowing or row hoeing was combined with under-sown cover crops make them interesting control methods for future research. Delaying tine cultivation by a few days after harvest did not reduce E. repens control, but a delay by 20 days tended to result in higher E. repens rhizome biomass and shoot densities, compared to performing it within a few days of harvest. Repeated tine cultivation did not improve control of E. repens or increase subsequent cereal yield, compared to a single cultivation directly after harvest. Repeated cultivation during autumn should therefore not be used categorically, but only when there is reason to believe the shoots will pass the compensation point due to the autumn conditions. We conclude that a site specific approach is necessary to achieve resource efficient control of E. repens.

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Two potential control methods for Elymus repens, which do not disturb the soil, are post-harvest mowing and competition from under-sown cover crops. Our aim was to quantify the effect of cover crop competition and mowing on E. repens and to evaluate the potential for combining the two methods. We present a two-factorial split-plot experiment conducted at three locations in Sweden, in two experimental rounds conducted in 2011–2012 and 2012–2013. A spring cereal crop was under-sown with perennial ryegrass, red clover or a mixture of the two (subplots). Under-sown crops were either not mowed, or mowed once or twice post-harvest (main plots). This was followed by ploughing and a new spring cereal crop the next year. Mowing twice reduced autumn shoot biomass by up to 66% for E. repens and 50% for cover crops compared with the control, twice as much as mowing once. Pure ryegrass and mixture treatments reduced E. repens shoot biomass by up to 40% compared with the control. Mowing twice reduced rhizome biomass in the subsequent year by 35% compared with the control, while the pure red clover treatment increased it by 20–30%. Mowing twice and treatments including red clover resulted in higher subsequent grain yields. We concluded that repeated mowing has the potential to control E. repens, but a low-yielding cover crop has insufficient effect on rhizome biomass. Clover–grass mixtures are of interest as cover crops, because they have the potential to increase subsequent crop yield and even at low levels they reduce E. repens above-ground autumn growth.