Publikasjoner
NIBIOs ansatte publiserer flere hundre vitenskapelige artikler og forskningsrapporter hvert år. Her finner du referanser og lenker til publikasjoner og andre forsknings- og formidlingsaktiviteter. Samlingen oppdateres løpende med både nytt og historisk materiale. For mer informasjon om NIBIOs publikasjoner, besøk NIBIOs bibliotek.
2006
Abstract
The aim of this three-year study (2001"2003) was to optimize fungicide application against anthracnose (Colletotrichum acutatum) in sweet and sour cherry orchards. The experimental sprays were applied to trees receiving normal fungicide programmes (grower schedule), although without the use of dithianon, except for the first year where only the experimental applications were applied to the sour cherry trees. Fungicide treatments were applied with either dithianon or copperoxychloride added prior to flowering or with dithianon added after flowering. Spraying with dithianon or copperoxychloride prior to flowering did not significantly reduce anthracnose compared to untreated. Two applications with dithianon during the green fruit stage (from petal fall and during the following 3"4 weeks) greatly reduced anthracnose at harvest. Three applications on green fruit did not reduce disease more than two applications. In sweet cherries, two sprays with dithianon at the green fruit stage in addition to the grower schedule reduced anthracnose at harvest from 14% to 3% in 2002 and from 15% to 1% the following year. In 2001, when very few fruit developed anthracnose, no treatment effects were evident. Treatments on green sour cherry fruit similar to those on sweet cherries reduced the attack of anthracnose from 85% to 42% in 2002 and from 51% to 12% the following year. In 2001, no treatment included only sprays on green fruit. However, one treatment, which included copperoxychloride at bud burst, one application of dithianon during flowering and two applications on green fruits, reduced anthracnose from 27% to 9%. Based on these results, cherry growers are recommended to spray twice with dithianon on green fruit if they have a history of anthracnose in their orchards.
Authors
Silje Aase WolffAbstract
Bladgjødsling med silisium (Si) er effektivt mot meldugg hos agurk. Både intensiteten og omfanget av melduggangrepet reduseres. Bladgjødsling med Si er et godt alternativ til miljøbelastede sprøytemidler og gir minimal sviskade. Ved å tilføre silisium som bladgjødsling unngår en dessuten tidligere problemer med høy pH i næringsløsningen og tilstopping av dryppvanningsanlegg
Abstract
Temporal changes in the scores of selected soil fertility indices were studied over six years in three different cases of organic crop rotation located in southern, eastern and central Norway. The cropping history and the initial scores of fertility indices prior to conversion to organic cropping differed between the sites. Crop yields, regarded as an overall, integrating fertility indicator, were in all rotations highly variable with few consistent temporal trends following the first year after conversion. On the site in eastern Norway, where conversion followed several years of all-arable crop rotations, earthworm number and biomass and soil physical properties improved, whereas the system was apparently degrading with regard to P and K trade balances and contents in soil. On the other two sites, the picture was less clear. On the southern site, which had a relatively fertile soil before conversion, the contents of soil organic matter and K decreased during the six-year period, but the scores of other fertility indices showed no trends. On the site in central Norway, there were positive trends for earthworm-related indices such as worm biomass and tubular biopores, and negative trends for soil porosity. The results, especially those from the eastern site, illustrate the general difficulty in drawing concllusions about overall fertility or sustainability when partial indicators show divergent trends. Consequently, the study gave no unambiguous support to the initial working hypothesis that organic farming increases inherent overall soil fertility, but rather showed that the effect varied among indicators and depended on status of the cases at conversion. It is concluded that indicators are probably better used as tools to learn about and improve system components than as absolute measures of sustainability.
Authors
Sverre Kobro Geir Kjølberg KnudsenAbstract
Det hender at det er mark i eplene. Markene er larver av en liten sommerfugl. Den heter rognebærmøll fordi den normalt utvikler seg i bærene på rogn. I enkelte år er det for lite bær på rogna, bare da kan møllet angripe eple.
Authors
Jens KøhlerAbstract
Det er ikke registrert sammendrag
Authors
Atle Hauge Hans Olav Eggestad T. Sveistrup Tore SveistrupAbstract
Det er ikke registrert sammendrag
Abstract
Methods for measuring prevalence of Neozygites floridana in a Tetranychus urticae population collected from strawberries were developed and compared. T. urticae were extracted from leaves using a soapy water solution (0.5 ml washing detergent : 8 l water) and then placed into 80% alcohol for use in methods 1 and 2. Method 1: N. floridana-sporulating T. urticae cadavers were observed and quantified under a compound microscope (40-80X). Method 2: Adult females were mounted in lactophenol cotton blue and observed for the presence or absence of N. floridana hyphal bodies under a microscope (200-400X). Method 3: Live T. urticae females were incubated at 25ºC and 75% RH and observed for mortality and N. floridana infection under a compound microscope (6.4-40X). Method 1 was the most time-efficient method and it also allows processing of samples as time permits. Method 2 quantified significantly higher fungal prevalence than method 1 and 3, but method 2 is not considered to be reliable because hyphal bodies are difficult to detect. No significant differences were found between methods 1 and 3.
Abstract
Freezing and thawing influence the transport potential and pathways for contaminants by altering the soil physical properties. Firstly, soil frost delays or impedes infiltration of rain and meltwater, reducing the transport rate of dissolved contaminants. But at the same time, particle bound contaminants may be mobilised because the reduced infiltration capacity increases surface runoff and erosion risk. Secondly, freezing water expands and imposes mechanical stresses on the soil, which may cause aggregate breakdown and facilitate particle detachment and transport. The influence of repeated freezing and thawing on aggregate stability of different soils is poorly documented for Nordic winter conditions. The purpose of this study (Kværnø and Øygarden, subm.) was to quantify the effect of variable freeze-thaw cycles and soil moisture conditions on aggregate stability of three soils: Silt, structured clay loam (Clay A) and artificially levelled silty clay loam (Clay B). These soils are representative of two erosion prone areas in South-eastern Norway. Field moist surface soil was sieved into the fraction 1- 4 mm, and packed into cylinders. The water content of the soil was adjusted, corresponding to matric potentials of -0.75, -2 and -10 kPa. The soil cores were insulated and covered, and subjected to 0, 1, 3 or 6 freeze-thaw cycles: freezing at "15"C for 24 hours, and thawing at 9"C for 48 hours. Aggregate stability was measured in a rainfall simulator (representing rainfall) and a wet-sieving apparatus (representing surface runoff). The aggregate stability of Silt was found to be significantly lower than of Clay A and Clay B. Clay A and Clay B had similar aggregate stabilities, even if it was expected that the artificially levelled Clay B would have lower stability. Freezing and thawing decreased the aggregate stability for all three soils, but the effect was more severe on the silt soil. There was no evident effect of water content on the aggregate stability, probably due to experimental limitations. The wet-sieving apparatus resulted in less aggregate breakdown than the rainfall simulator. Rainfall impact seemed to be more detrimental than wet-sieving the more unstable the soil was, that is, after many freeze-thaw cycles, and on silt soil. The results indicate that freezing and thawing is an important factor influencing the erosion risk of the studied soils. In the future, climate change is expected to give more unstable winters with more freezing and thawing events. Combined with more precipitation as rainfall during the winter period both runoff and erosion will probably increase, possibly resulting in heavier loads of particulate bound contaminants to surface waters. The results are also helpful for improving predictions of contaminant fate and transport, as most of the existing hydrological and soil erosion prediction models do not satisfactorily describe soil processes occurring under Nordic winter conditions. This study focused on arable soils with conventional agricultural management, where plant nutrients and pesticides pose a threat to water quality. It would be useful to conduct similar experiments on soils where other organic and inorganic contaminants are of concern, e.g. on soils where sewage sludge and compost have been applied, and soils in road cuttings and on contruction sites. References Kværnø, S.H. & Øygarden, L. submitted: The influence of freeze-thaw cycles and soil moisture on aggregate stability of three soils in Norway.
Abstract
Grønnsakdyrking foregår ofte på intensivt dyrkede arealer med tilførsel av store mengder næringsstoffer, noe som gjerne fører til store overskudd i næringsbalansen. Tap av næringsstoffer fra slike arealer er som regel større enn fra øvrige jordbruksarealer. Risiko for avrenning av fosfor er særlig stor på grunn av generell sterk fosforgjødsling og ved at slike åkerkulturer er mer utsatt for jorderosjon, særlig etter høsting i forbindelse med sterke nedbørsepisoder.
Authors
Shala Werner Michael Albers Terry Cryderman Danko Dimenic Robert Heyd Boris Hrasovic Sverre Kobro Stig Larsson Roger Mech Pekka Niemela Matti Rousi Kenneth Raffa Kyoko Scanlon Shane WeberAbstract
The introduced basswood thrips, Thrips calcaratus, undergoes outbreaks on and damages American basswood, Tilia americana, in North America, but is less common on and does not cause significant damage to little-leaf linden, Tilia cordata, in its native European range. A possible explanation is that altered host relationships in North America allow increased exploitation of T. americana. Three experiments were conducted to compare host associations of T. calcaratus between T. americana and T. cordata. In a laboratory choice bioassay, T. calcaratus occupied foliage of both tree species with equal frequency. A field assay conducted in North America revealed an identical trend on planted T. americana and T. cordata seedlings planted in a paired design. In a separate field experiment bud break phenology, peak T. calcaratus emergence, and foliar development showed similar temporal patterns in 10 T. cordata and T. americana sites distributed across the insect"s native range of Europe and introduced range of North America. These results suggest that physiological and phenological differences between native and newly acquired Tilia hosts are not likely responsible for the increased impact of T. calcaratus in its introduced range. Rather, temporal escape from natural enemies seems to be the more likely explanation. This is evidenced by the stronger synchrony of the North American predator, Leptothrips mali, with the native basswood thrips, Neohydatothrips tiliae, than with T. calcaratus. Understanding the basis for increased success of T. calcaratus in its introduced range may provide insight into managing this insect in basswood forests in the Great Lakes region.