Induced defence reaction in the phloem of spruce ( Picea abies) and larch ( Larix decidua) after attack by Ips typographus and Ips cembrae

Abstract

The physiological reaction of larch ( Larix decidua) and spruce ( Picea abies) after attack by Ips cembrae and Ips typographus, respectively, was investigated from 1991 until 1993 by analysis of the constituents of phloem tissue (soluble carbohydrates, protein amino acids, pinitol, shikimic acid, quinic acid, catechin, procyanidines). To exclude behavioural artefacts, the investigation was performed under natural field conditions with free choice of their host by both bark beetle species. A sequence of resistance mechanisms was detected after attack. Dependent upon the intensity, the duration, and the success of the attack at first locally limited changes in the metabolism of attacked trees occurred. These changes resulted in a deterioration in the food quality (shift of the nutrient/inhibiting compounds ratio in favour of the latter) with the effect of disturbing the establishment of the beetles. With stronger and longer lasting attack, long-lasting systemic changes in the metabolism of the whole tree were induced. These resulted, likewise, in a deterioration of the nutrient/inhibiting compounds balance, an increase of the protein biosynthesis and an intensification of the defence metabolism. This reaction was sustained with successful attack until the end of the development of the brood beetles. Thus, the induced resistance reactions were directed against the parent generation and the brood alike, extending from the level of the individual tree to the level of the population of trees.