The spatial distribution and density of the emerald ash borer infestation in Rock Island and Moline, IL

The Emerald Ash Borer (EAB) Agrilus planipennis Fairmare (Copleoptera: Buprestidae) is a destructive colonizer of ash trees that arrived in the United States in 2002. Since then, EAB has been detected in 22 states and two Canadian provinces, and has proven to be a complicated management issue for many cities including Rock Island and Moline, IL. The purpose of this study was to determine the spatial distribution and density of the EAB infestation in Rock Island  and Moline, IL and to identify potential correlations between host larval densities and visual symptoms. Spatial distribution was determined through a trapping survey, with a total of 63 beetle traps (roughly two per square mile quadrat) placed throughout both cities. Two different trap types were used (green or purple multifunnel traps and purple prism traps) and all traps were baited with Manuka oil and z-3-hexanol lures. Larval density and potential correlations with visual symptoms were determined by removing two 50cm branch segments from ash trees. Branch segments were whittled in 1mm thick sheets until the cambium was reached while recording the number of larvae and galleries. Visual symptoms including ash canopy rating, bark splitting, epicormic shooting, and exit holes were assessed for each tree used in the trapping survey and branch sampling. No EAB beetles were found outside the invasion epicenter at Hasselroth Park in Rock Island, IL. Larval density in sampled branches averaged 3.2 larvae per  50cm branch, and there was no significant relationship between larval density and the presence of any visual symptoms.