Dynamics of Larch Bud Moth Populations

Abstract

Ideally studies on the population dynamics of organisms should be holistic, general, precise, and realistic (64). Much too often, however, support for research on forest pests approximates the curve of the gradations in time and space, resulting in periodic gathering of bits and pieces of information that differ little from that gathered earlier or elsewhere (68). Therefore it is not surprising that lack of compre hensive, quantitative information on many generations of a field population has handicapped the progress of theoretical thinking on the dynamics of populations, which badly needs "more light and less heat " (86). It has been proposed that research efforts should be coordinated internationally on a few model insects in order to cope with complexity and diversity of population dynamics at a high level of efficiency (25). We consider that the larch bud moth, Zeiraphera diniana, would meet the criteria for being such a model insect (18). The coincidence of large-scale insect outbreaks, the availability of effective insecti cides, and economic expansion of industry and tourism after World War II pro moted several extensive control actions against such forest pests as the spruce budworm, Choristoneura fumiferana, in eastern Canada and the larch bud moth, Z. diniana, in Switzerland. Public demand to protect the subalpine larch forests in the recreation area of the Engadine (Switzerland) against the recurring defoliation by the larch bud moth triggered the present research phase. This article is the first attempt to publish the results of the research period (1949-1975) comprehensively. In addition, information concerning previous outbreaks of Z. diniana is reviewed on a worldwide base.