Density and location of simulated signs of injury affect efficacy of ground surveys for Asian longhorned beetle

Abstract

Surveys for signs of attack by Asian long-horned beetles, Anoplophora glabripennis (Motschulsky) (Coleoptera: Cerambycidae), currently rely upon visual examination of trees to discover signs of attack. By embedding simulated A. glabripennis oviposition pits and exit holes on open-grown Norway maples, Acer platanoides L. (Aceraceae), we evaluated the effect of sign density, height (below or above 2.5m), and position (bole or branch) when foliage was present or absent on inspector ability to distinguish trees with or without signs. From this, we quantified detectability, or the proportion of trees correctly identified as infested, and determined the time taken to do so. Effectiveness in detecting trees with signs improved when sign density increased, when signs were below 2.5m, and when oviposition pits were located on boles and exit holes on branches. These main findings require some caveats, due to a number of significant interactions. Foliage presence/absence had no apparent influence on effectiveness; possible reasons are provided for this result. Time-to-find curves, which illustrated the proportion of inspectors who accurately identified an infested tree as a function of survey duration, revealed that for most treatment combinations, most infested trees were detected within the first 2 min of survey time. These findings provide baseline data to assist managers in designing effective protocols for ground surveys of A. glabripennis.