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NIBIOs employees contribute to several hundred scientific articles and research reports every year. You can browse or search in our collection which contains references and links to these publications as well as other research and dissemination activities. The collection is continously updated with new and historical material.



To test the pathogenicity of Ips typographus-associated fungi to Norway spruce, trees were inoculated with four species, Ophiostoma polonicum, O. bicolor, O. penicillltum and Graphium sp. Trees inoculated with the three Ophiostoma species produced strong hypersensitive responses in the phloem and exuded more resin than did the control trees. Only O. polonicum was able to invade the sapwood and consequently able to kill trees. Inoculation with Graphium sp. gave the same response as inoculation with the control.


The paper reports on changes in physical properties of growth media/substrates caused by frequent drying before re-irrigation. The peat/perlite mixtures were systematically dried to defined levels for 104 days in single pots, each including one Norway spruce seedling. Irrigation regimes were defined in relation to the volume of liquid in the substrates at container capacity when the experiment started (initially). Single pots were re-irrigated with nutrient solution as 10, 30, 50 and 70 % of that volume of liquid was consumed. Growth substrate volume and bulk density, and the fraction of perlite mixed with the peat were measured initially and at the termination of the experiment (finally). The volume fraction of gas filled pores was obtained gravimetrically at least once a day to describe changes in the liquid status of the growth substrates. The volume of substrate stayed constant in all irrigation regimes during the experimental period. The bulk density was independent of the fraction of perlite, but it was lower finally than initially for substrates subjected to the most frequent irrigation. The initial volume fraction of gas filled pores was negatively correlated with the initial bulk density, and the linear regressions depended on the fraction of perlite. The volume fraction of gas filled pores at container capacity (fgcc) increased during the experiment from .33 to .50 ml ml-1 for substrates subjected to the most dry conditions, and from .33 to .41 ml ml-1 in regimes allowing 30 and 50 % liquid losses. For substrates subjected to the least dry conditions, fgcc decreased from .30 to .26 ml ml-1. Initial and final fgcc was positively correlated. The linear regressions were different for the different irrigation regimes as indicated by their average changes described above.


Fifty pole stage trees were inoculated with O. polonicum at monthly intervals between May and September. Most infection, measured as the area of sapwood blue-stained, occurred in July and least in May and September. The difference between July, August and September might be explained by the effect of temperature on fungal growth, but in May and June the trees had a higher resistance than expected. Tree resistance was correlated with resinosis. Tree variables not correlated with resistance were DBH, annual ring width, periodic growth, vigor index, or phloem carbohydrate concentration.