Distribution of <i>Anoplophora glabripennis</i> (Coleoptera: Cerambycidae) damage in tree canopies: implications for survey efficacy

Anoplophora glabripennis Motschulsky is an invasive woodboring beetle in North America and Europe that threatens a broad range of tree genera. Eradication is a costly and time-consuming process that requires visual surveys to detect beetle damage on host trees. Knowing the distribution of beetle damage within trees could directly benefit survey efforts by focusing surveys on high-risk areas and indirectly by identifying habitat factors that structure beetle populations. In the A. glabripennis infestation in South Carolina, we identified an isolated and actively growing subpopulation on an island that had not fully occupied the available host trees. With host resources still abundant for the beetle, the distribution of oviposition pits and exit holes is expected to be the result of habitat preference and (in the case of exit holes) larval performance. We examined the distribution of eggs and emerging adults by cataloging the >14,000 oviposition sites and >1,400 exit holes distributed among the 33 infested and uninfested host trees on the island, documenting the stem height, diameter, surface area, and bark thickness for all damage. Oviposition pits and exit holes were neither randomly nor evenly distributed within tree canopies; however, the distribution of available habitat (ie stem space within the canopy) seemed to drive most of the distribution, and the presence of damage was biased toward larger/taller trees. These results suggest some preference in egg placement with regard to canopy height, stem diameter, and bark thickness within canopies, but the responses are subtle and may have limited utility in guiding visual surveys.