The pine shoot beetle (Tomicus piniperda; Coleoptera: Scolytidae) is native to Eurasia where it attacks primarily pine trees (Pinus). This beetle was discovered in Ohio in 1992 and as of March 1998 it has spread to 224 counties in nine US states (Illinois, Indiana, Michigan, Ohio, Pennsylvania, New York, Maryland, West Virginia and Wisconsin) and to 18 counties in Ontario, Canada. In 1992, a federal quarantine was imposed by USDA APHIS (Animal and Plant Health Inspection Service) on the movement of pine from infested counties to uninfested counties within the US. The quarantine regulates the movement of pine logs, pine Christmas trees, and pine nursery stock. The quarantine allows managers to ship their pine products during specific times of the year based on the biology of the beetle. Currently a single set of dates is used for the entire 9-state infested area. However, it is recognized that considerable climatic variation does occur within the infested region. Furthermore, as the pine shoot beetle continues to spread, even greater variation in climatic conditions will occur on average from north to south. Therefore, APHIS became interested in developing a series of dates that could help predict behavior of the pine shoot beetle in different parts of its US range throughout the year.
This study addresses two temperature-dependent aspects of the pine shoot beetle's life history that are very relevant to the quarantine, i.e., the initiation of adult flight in spring and the initiation of shoot departure in fall. We used historical weather records (1950-1993) for the 21-state northeast quadrant of the US to develop isopleth maps for average dates for when spring temperatures will first support adult flight (55-60 F), and for the first occurrence of hard frosts in autumn (24 and 28 F). Temperature data were averaged for each recording station in the 21-state region and then isopleth maps were developed with Kriging software. The isopleth maps were presented to APHIS for their use in adjusting the quarantine in a fashion that is biologically relevant as well as practical to both managers and regulators.
In addition, we tested the accuracy of these maps with actual dates of initial spring flight and initial fall shoot departure for various sites in Indiana and Michigan. Moreover, we recorded air, duff, and inside bark temperatures in spring as well as air and inside-twig temperatures in fall to test whether air temperatures accurately reflect the environment where the beetles reside.