Hopp til hovedinnholdet


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.



During an outbreak in the 1970\"s, millions of Norway spruce trees were killed by the spruce bark beetle Ips typographus. At that time, little was known about the associated fungi and their role in the tree-killing process. Studies were started to elucidate ecological aspects of fungi associated with I. typographus, with special emphasis on the fungal invasion process.I. typographus has no mycangium and caries a variety of fungal spores, externally in pits on the pronota and elytra and internally within the digestive tract. Spores are also transmitted by phoretic mites. Most species belong to Ophiostomataceae and confusions within some important species have been put right. The fungal flora aseetle, but with some variations. Four species proved to be common in Norway, but Ophiostoma polonicum was more frequent in epidemic areas man in endemic areas . The frequency of this species is thus suspected to increase during epidemics. Studies during epidemic conditions revealed that the fungi invaded the sapwood of infested Norway spruce trees in an obvious succession, with O. polonicum in the leading edge of fungal penetration until heartwood was reached. The species found to be most commonly transmitted by I. typographus were shown to be first in the succession.The temperature is important for the rate of fungal invasion and the development of visible blue-stain, which occurred close to the leading edge of fungal penetration. The fungal colonization of sapwood leads to a gradual decrease in the moisture content, followed by desiccation symptoms in the foliage of infested trees. The tree trunks soon reached a moisture level not favourable for decaying Hymenomycetes, except near the base of the trees.The primary invader O. polonicum appeared to be pathogenic to Norway spruce trees when mass inoculated, while the secondary invaders were not at the given load of infection doses. However, the inoculation doses are of importance for the success of inoculated fungi. Judging from the large reaction zones in the phloem made by same secondary invaders, they may play an important role in the tree killing process in areas with low frequencies of O. polonicum. O. polonicum can kill other species of spruce used in European forestry and Douglas fir, so the fact that conifers other than Norway spruce rather rarely are attacked by I. typographus seems not to depend on the absence of a pathogenic fungus to overwhelm the trees.The fungi associated with I. typographus are sensitive to the lesion resin produced by Norway spruce trees in response to the fungal invasion. The potential of O. polonicum to be a primary invader seems to be linked to its rapid growth rate and ability to grow for a prolonged period under oxygen-deficient conditions. In conclusion, it seems that the interrelationship between Norway spruce, I. typographus and associated fungi is similar to other interrelationships. One of the associated fungi, O. polonicum, appeared lo play a key role in overwhelming infested trees due its abilily to grow for a prolonged period in wood with low oxygen pressure.


The Eurasian sprucc bark beetle, Ips typogaphus carries spores of several fungi induding Ophiostoma bicolor, O. pellicillatum and O. polonicum. However, after attack on Norway spruce trees O. polonicum is the pioneer invader of the sapwood while other species follow. To determine the causes behind this distinct succession experiments were performed comparing growth rate, tolerance to oxygen-deficient conditions and to spruce resin between these early invaders. In sealed tubes with limited oxygen. O. polonicum grew for a longer time than three other species regularly associated with I. typagraphus in Norway. The non-volatile components of lesion resin induced by fungal attack, as opposed to preformed resin, inhihited the growth of all species, but partirularly O. polonicum. O. polonicum grew rapidly on malt agar, but not faster than some of the other species associated with I. typographus. It is concluded that rapid growth and the abilily lo tolerate low oxygen pressure are important attributes for primary invaders, allowing tree resistance mechanisms to be overcome following mass inoculation.



In a field experiment in southernmost Norway four young trees of each of eight coniferous species were subjected to artificial inoculation with the pathogenic blue-stain fungus Ophiostoma polonicum, associated with the spruce bark beetle Ips typographus. A dose previously known to be lethal to most Norway spruce trees also killed individuals of Sitka, white, and black spruce, and Douglas fir. All Scots and lodgepole pines, and subalpine firs survived the given load of infection. Douglas fir did not exhibit the induced resinous defence reaction seen in spruce and pine. The fungus did not proliferate in the phloem of Douglas fir, but spread more easily in a tangential direction in the sapwood of this species than in spruce.