Introduction

The emerald ash borer (Agrilus planipennis Fairmaire, Coleoptera: Buprestidae) (EAB) is a wood-boring beetle native to Asia that was initially discovered in the United States in June 2002. It most likely entered the country in solid wood packing material such as crates and pallets and was transported to Detroit, Michigan, at least 10 years before it was discovered in 2002 (Cappaert and others 2005, Herms and others 2004). Ash trees are the only known host, and damage is the result of larval activity. Once eggs hatch, larvae bore into the cambium and begin to feed on and produce galleries in the phloem and outer sapwood. Larval feeding disrupts the translocation of water and nutrients and eventually girdles the tree. Tree mortality occurs within 1 to 3 years, depending on severity of the infestation (Haack and others 2002, McCullough and Katovich 2004). All of Michigan’s native ash species (Fraxinus spp.) and planted cultivars are susceptible (Cappaert and others 2005). Since 2002, southeastern Michigan has lost an estimated 15 million ash trees due to EAB (Cappaert and others 2005).

The natural rate of EAB dispersal is estimated to be less than 1 km per year in low-density sites. Natural dispersal has been enhanced by human transportation of infested firewood, ash logs, and nursery stock. This artificial spread of EAB has initiated the majority of outlier infestations (Cappaert and others 2005). Continued spread outside of the core zone increases the threat to ash across the United States.

The objective of the study was twofold: (1) to illustrate methods of uncertainty analysis, and (2) to investigate the contributions of spatial correlation to the uncertainty of areal estimates. Although the study was motivated by the need to predict the magnitude of potential loss of ash trees due to the EAB, the biological context for this study was simply a medium to address the uncertainty objectives; no results from this study regarding the EAB or its effects should be construed as definitive.