Publications
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.
1996
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Authors
Paal KrokeneAbstract
Aggressive bark beetles kill healthy conifers through pheromone-mediated mass attacks. The exact mechanism by which trees are killed is still disputed, but phytopathogenic blue-stain fungi associated with the beetles are probably involved in most cases. This thesis compares the blue-stain flora of five bark beetle species that colonize Norway spruce of different resistance. The aggressive Ips typographus can kill healthy trees, while the other species are non-aggressive and colonize either severly stressed or dying trees (the facultatively parasitic Ips duplicatus, Polygraphus poligraphus and Pityogenes chalcographus), or dead trees (the saprophagic Hylurgops palliates). Ips typographus and I. duplicatus were both found to carry very high frequencies of the phytopathogenic fungus Ceratocystis polonica. This fungus has previously been found associated only with I. typographus, and has been shown to be pathogenic to Norway spruce in experimental mass inoculations. The other bark beetles carried no known pathogenic fungi. The phytopathogenicity of four of the isolated blue-stain fungi were evaluated through mass and low-density inoculation in young Norway spruce trees. Mass inoculations confirmed C. polonica\"s pathogenicity, while the other fungi, which are associated with non-aggressive beetles, were not pathogenic (Ophiostoma piceae, cfr. Ambrosiell sp., Dark sterile sp.A). Low-density inoculations revealed only small differences between the four fungi in phloem necrosis length. Necrosis length is used as a standard criterion of fungal pathogenicity, but it was not useful for assessing the pathogenicity of the fungi in the fungus-host tree system under study here. Ceratocystis polonica was found to penertrate deeper into the sapwood and induce deeper sapwood desiccation than the other fungi. The ability to invade sapwood is probably more important for fungal pathogenicity than the ability to colonize phloem, and may thus be a better criterion for assessing the pathogenicity of blue-stain fungi. General aspects of the association between bark beetles and blue-stain fungi are discussed.
Authors
Ingolf Nes Dzung Bao Diep Leiv Sigve Håvarstein May Bente Brurberg Vincent Eijsink Helge HoloAbstract
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Marit Slåttelid Skeie May Bente Brurberg P.H. Middelhoven Gunnar Fimland Jon Nissen-Meyer Ingolf F. Nes Vincent G. H. EijsinkAbstract
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1995
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