The fungus, Geosmithia morbida, vectored by the walnut twig beetle, Pityophthorus
juglandis, has been associated with disease outbreaks in walnut (Juglans spp.) and wingnut species (Pterocarya spp.), known as Thousand Cankers Disease (TCD). How did Geosmithia spread across North America? Can we identify separate genetic populations? Do they have different pathogenicity and virulence to walnut trees? How are the evolution and spread of the beetle and the fungus interrelated? To answer some of these questions we will use a population genetics to understand co-evolution of the pathogen-vector complex using microsatellite loci. Analysis will include using allelic based data to understand genetic diversity and model temporal-spatial distribution.