Biological Control in
Cool Temperate Regions
David A. Andow, David W. Ragsdale,
and Robert F. Nyvall
Since the first spectacular success more than a hundred years ago, biological control efforts have expanded, covering cropping systems worldwide. Biological control has grown to encompass several approaches: inoculation, inundation, and conservation. Inoculative methods involve introducing the biological control agent in relatively small numbers so that when it increases it will control the target pest. The classical inoculative method (abbreviated as the classical method) requires only one or a few inoculations to establish a self-reproducing population of biological control agents, while the seasonal inoculative method requires repeated seasonal introductions. Inundative methods involve introducing the agent in large enough numbers to suppress the target pest immediately. Conservation methods involve modifying the environment to retain and enhance the agent, thereby facilitating greater levels of control. Several books provide a summary of recent advances in the field ( Wood and Way 1988; Baker and Dunn 1989; Hornby 1990; Charudattan 1991; Andrews 1992; Cook 1993; Yang and TeBeest 1993) and frame some of the contemporary conceptual issues ( Mackauer et al. 1990), but because the field is so vast, it has not been reviewed uniformly since Clausen 1978 effort, which summarized worldwide efforts using the classical inoculative method against weed and arthropod pests, and Cook and Baker 1983 review of efforts related to plant pathogens. Here we break from previous treatments of biological control and, instead of attempting a worldwide coverage of the field, we focus on biological control in a restricted geographic area, the cool temperate region.
Worldwide, cool temperate regions occur polar to the Mediterranean and great desert climatic regions, which is generally north of 40°N latitude in North America and Asia and north of 45°N in Europe. These regions include the dry midlatitude steppes of Central Asia, the western Great Plains of North America, the humid mesothermal west coast marine climates of the Pacific Northwest and Western Eu-