Zeiraphera griseana Hübner (Lepidoptera: Tortricidae) in the European Alps. A Contribution to the Problem of Cycles

Abstract

The grey larch budmoth, Zeiraphera griseana Hb., defoliates the extensive larch forests of the European Alps at intervals of from six to eight years. Historical records on the development of visible damage for ten gradations, together with quantitative results on the population dynamics of the last full gradation, provide the explanation of this cyclic phenomenon. Average weather conditions allowing a steady population increase, the deciduous habit of the host tree, and a high rate of increase constitute a simple ecological situation which results in regular oscillations of populations of this insect.