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.
1992
Authors
Halvor SolheimAbstract
Healthy Norway spruee trees were investigated over 130 weeks following successful attack by the bark beetle Ips typographus in a study of fungal invasion. The study was undetaken in southeastern Norway during an epidemic period. Sapwood moisture was measured and the tree reaction and beetle activity were noted. Fungal invasion was examined in disc samples taken 1, 5, 10 and 15 m above stump height. The fungal penetration in the sapwood started very slowly, but accelerated during the fouth week after attack. The leading edge of fungal penetration was a few millimeters in advance of the visible blue-stain until the heathwood was reached. The development of blue-stain was similar in Lardal, 1979, and at S, 1980, but with some differenees relatea to the air temperature. Fungi were found to invade the sapwood successively. The pathogenic species, Ophiostoma polonimm, was the primary invader occurring during the first week, followed by other beetletransmitted species. The secondary invaders, O. bicolor; Graphium sp. 1, O. penicillatum and O.ainoae, entered the sapwood during the first three weeks after attack and reaehed a peak within ten weeks. The tertiary invaders, probably also beetle transmitted, were not as common as the secondary colonizers. The first Hymenomycetes, rather weak white-rotters, appeared among the tertiary invaders. Later succession was dependent on the moisture content of sapwood. Strong decaying whiterotters entered the sapwood near the base where the moisture content remained favourable, while cf. Trichoderma viride dominated in the drier parts of the trees, where the sapwood moisture declined to fibre saturation point 75 weeks after attack. The heavy beetle attack, averaged 3.7 entrance holes per dm2 over more than ten meters of the stem, overwhelmed the trees rapidly and no secondary resinosis occurred.
Authors
H. Sverdrup P. Warfvinge Tore Frogner Arnt-Olav Håøya M. Johanson B. AndersenAbstract
No abstract has been registered
Authors
Ivar SamsetAbstract
No abstract has been registered
Authors
Erik ChristiansenAbstract
The defence of Norway spruce against a combined attack of the bark beetle Ips typographus and its associated blue-stain fungi is based upon a) constitutive resin stored in ducts of the bark and sapwood, and b) induced resinosis in reaction zones surrounding the point of infection. Empirically, beetle epidemics are associated with external stresses, drought being a particularly prominent factor. An attempt was made to mechanistically explain the apparent link between drought and infestations, through studying after-effects of drought on the induced defence in stressed trees. In the field, 3-5.5 m tall trees were exposed to artificial drought over three growth seasons to investigate whether this treatment would predispose them to fungal infection in a fourth season when drought was absent. Pre-dawn xylem water potentials down to -1.85 MPa and a considerable foliage depletion were recorded. In the fourth season, the trees were inoculated with Ophiostoma polonicum, a pathogenic associate of Ips typographus. No difference in susceptibility could be seen between drought stressed trees and unstressed controls. Carbohydrate concentrations of foliage and branch bark were slightly enhanced and mineral nutrient concentrations strongly reduced in stressed trees.
Authors
Erik NæssetAbstract
No abstract has been registered
Authors
Dan AamlidAbstract
No abstract has been registered
Authors
Dan AamlidAbstract
No abstract has been registered
Authors
B. Långstrøm Claes Hellqvist Halvor SolheimAbstract
No abstract has been registered
Abstract
No abstract has been registered
Authors
Arne Olav Stuanes I. Andersson Nancy B. Dise H. Hultberg O. Janne Kjønaas Per Holm Nygaard U. NyströmAbstract
No abstract has been registered