AUTHORS: Brian R. Sturtevant*, USDA Forest Service; Matthew Garcia, University of Wisconsin; Jacques Régnière, Yan Boulanger, Barry J. Cooke – Natural Resources Canada; Joseph J. Charney, Gary L. Achtemeier – USDA Forest Service; Johanne Delisle, Marc Rhainds, Rémi Saint-Amant – Natural Resources Canada
ABSTRACT: The spatiotemporal dynamics of eastern spruce budworm outbreaks in North American boreal and sub-boreal forests may be sensitive to long-distance dispersal patterns that are assisted by meteorological processes. We provide an overview of temperature-constrained functional relationships between insect mass, wing area, and wingbeat frequencies, and employ these relationships to simulate realistic flight altitude distributions. An agent-based model of budworm flight, conditioned on mesoscale numerical weather simulations of temperature and wind fields, produces vertical flight density distributions that arise in combination with atmospheric boundary layer thermal profiles. We confronted our simulated moth density distributions with observed vertical profiles of moth density inferred from weather surveillance radar during budworm 2013 and 2017 outbreak events across the Gulf of St. Lawrence River in southeastern Canada. These data were used to iteratively refine the most uncertain flight parameters. Consequent dispersal patterns from broader-scaled budworm flight simulations were consistent with observations of long-distance migration events at sites in southern Quebec and New Brunswick (Canada) and in northern Maine (USA). We were able to validate outbreak source populations using a distinct indicator in differential loadings of parasitic mites. The biologically-based and meteorologically-conditioned budworm flight model holds promise as an operational tool for assessing budworm outbreak events, with the potential to inform both land management agencies and a concerned public as the eastern North American outbreak shifts into more human-dominated regions of the southeastern boreal and Acadian forests.
