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
Dan AamlidAbstract
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Dan AamlidAbstract
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Guro BrodalAbstract
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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
Halvor SolheimAbstract
Healthy Norway spruce trees infested by the bark beetle Ips typographus were investigated weekly for 10 weeks to examine the early stages in fungal invasion. The study was performed in southeastern Norway during an epidemic period. The fungal association consisted of Ophiostoma species and an undescribed Graphium species, which invaded the sapwood in an obvious succession. The pathogenic species Ophiostoma polonicum was the first invader of both phloem and sapwood and was always in the leading edge of fungal penetration into sapwood. Ophiostoma bicolor followed O. polonicum in the sapwood invasion. These species were successively replaced by Graphium sp. 1 , Ophiostoma pennicillatum and Ophiostoma ainoae. Ophiostoma pellicillatum seems to be more adapted to colonizing the phloem than the sapwood. The earliest invaders were the species most frequently carried by the beetles.