Modeling Potential Movements of a Ash Threat: The Emerald Ash Borer

Louis R. Iverson, Anantha Prasad, Jonathan Bossenbroek, Davis Sydnor, and Mark Schwartz

USDA Forest Service Northeastern Research Station (1-2), University of Toledo (3) , Ohio State University (4), and University of California-Davis (5)

The emerald ash borer (EAB, Agrilus planipennis) is threatening to wipe out native ashes (Fraxinus sp.) from the North American continent, and is so far doing this well across large sections of Michigan, Ohio, Indiana, and Ontario. We are attempting to model its future movement by adapting a model developed for the potential movement of tree species over a century of climate change. We have two model variants, an ‘insect-flight’ model and an ‘insect-ride’ model to assess potential movement.

With the ‘flight’ model, probability of movement is dependent on EAB abundance in the source cells (270 m cells), the quantity of ash in the target cells, and the distances between them. There is a low-level ‘background’ probability of long distance transport via storms, etc. To estimate abundance, we assume an 11-year cycle along a normal curve with maximum abundance at year 6 and minimum abundance at the initial colonization time as well as after the ash trees have died within the cell. For initial conditions of EAB abundance, we estimated zones of infestation each year from 1998-2005 via known EAB location and other data.

With the ‘insect-ride’ model, we have utilized GIS data to weight factors related to potential human-assisted movements of EAB-infested ash wood or just hitchhiking insects: roads, urban areas, tree nurseries, various wood products industries, and especially campgrounds. With campgrounds, we are developing a gravity model which considers traffic volumes and routes between EAB source areas and various distances to campgrounds. Each layer has buffer weights, which when combined results in a map of zones of enhanced probability of EAB colonization. We also intend to apply various ‘slow the spread’ efforts to see how these may affect spread so that various management strategies can be evaluated.

Exotic Pests Session - Tuesday Afternoon

corresponding author:

Louis R. Iverson
USDA Forest Service
Northeastern Research Station
359 Main Road
Delaware, OH 43015
740-368-0097
liverson@fs.fed.us