THE INFLUENCE OF LAND USE AND VEGETATION ON THE POPULATION DENSITY OF HYPHANTRIA CUNEA

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Abstract
The objects of this study were to determine whether the population density of Hyphantria cunea Drury is dependent on land use, vegetation pattern, and plant species; and to compare the extensive methods designed for this work with more intensive, single-plot designs.In two separate gradations, covering a period of 12 years, density was positively correlated with agricultural land use, open rather than closed patterns of vegetation, and the occurrence of only a few of the principal host species. The analysis showed how these variables affected density both within and between different climatic areas, and suggested how cultural methods might be used in population management.Extensive designs permit the development and testing of holistic models designed to explain both spatial and temporal differences in population density, and provide the replication required for the latter purpose. It is important to model spatial differences in density because such variables as vegetation pattern and composition are sometimes subject to cultural modification. Very intensive designs, based on sampling only a few trees at one point, do not permit the development of complete models and, because of plant host and dispersal phenomena affecting insects and their parasites, produce data that may be unreliable even for sub-models, such as those dealing with host–parasite interactions.