Bark beetle (Col., Scolytidae) colonization and tevpene patterns in the bark of Norway spruce (Picea abies Karst.) trap treesTra trees of the Norway spruce were used to investigate correlations between colonization density of bar[ beetles and terpene patterns of the trunk phloem. Ips ty ographus and Pityogenes chalcographus were the dominant species, which demonstrated the usuaI diierentiated patterns of attack concentration along the trunks. There were, however also exceptions made by P. chalcogruphus, extending its mass colonization down to more basical parts of the trunk.Phloem samples were collected from 7 trap trees, when bark beetle flight was just starting in middle of May 1985. Three samples per trap tree were each taken from the center of the bottom, middle and top third of the trunk, respectively, and analyzed by a G U M S device. The average density of enterance holes of I . ty ographus and P. chulcographus as calculated for each third of an individual sections.A strong positive correlation of P. chalcogruphus attack density was found to exist to myrcene, and to the P-pinene : a-pinene relation, and to P-phellandrene x limonene as well. Correlation was a little hi her, when these three terpene values were combined by addition. With I . typographus it was more difficult to find correlations with terpene contents of the bark. A r = 0.679 (p < 0.01) was calculated for the term (a-pinene x limonene): (myrcene x cam hene); neglecting some outliers correlation could be increased to r = 0.912. Considering the total numger of values, correlation is improved by addition of P-phellandrene: (A3-carene + 1) and tricylene x (terpinolene i 1) (r = 0.739, p < 0.001). It is suggested that the differing preference of I . ty ographus and P. chalcographus for completely different terpene patterns of the spruce phloem may pfay an im ortant role in host tree selection as well as in selection of the colonizaticfn site within a trunk. FurtKer experiments should demonstrate, whether these terpene fractions are involved in the "primary attraction principle" of Norway spruce to the investigated bark beetle species. trunk, was now compare B with the varying mono-and sesquiterpene patterns of the respective trunk 1 Einleitung Die Fichtenborkenkafer Ips typographus und Pityogenes chalcographus L. (Col., Scolytidae) spielen in weiten Teilen Europas seit jeher eine grode wirtschaftliche Rolle als Forstschadlinge. Obwohl beide Arten gemeinsarn auftreten, bestehen doch gewisse Unterschiede in der Praferenz des Brutsubstrates. Verschiebungen beziiglich der Dorninanz der beiden Arten zugunsten des P. chalcographus, wie sie in der letzten Zeit vielerorts beobachtet werden (FUHRER 1988, 1989), riicken die Frage nach den arttypischen Spezifika der Befallsdisposition der Fichte in den Vordergrund. Beobachtungen, dai3 an bestirnmten Standorten das Ausmad der Kronenverlichtung der Fichten auf die relative Akzeptanz der Fangbaume durch I. typographus und P. chalcographus Einflud nimmt (WIENER und FUHRER 1985; WIENER 1988), lieden vermuten, dai...
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