Spatial patterns of within-treeEnaphalodes rufulus(Coleoptera: Cerambycidae) attacks during outbreak conditions in the Ozark National Forest in Arkansas, United States of America

Abstract

AbstractEnaphalodes rufulus(Haldeman) (red oak borer; Coleoptera: Cerambycidae) is a native wood borer that colonises and develops in oaks (QuercusLinnaeus; Fagaceae) across southeastern Canada and the eastern United States of America. It is rarely considered a pest because it normally occurs at low population density levels in stressed or dying oak trees. In the late 1990s and early 2000s there was a large, historically unique outbreak ofE.rufulusin the Ozark mountains of Arkansas and Missouri, United States of America. This outbreak provided an opportunity to investigate within-tree spatial distribution of attacks during unusually high insect population levels. Fifty trees from northern Arkansas were felled and destructively sampled. The locations of attack sites by femaleE.rufuluswere standardised across varying heights and diameters for comparison across trees. Attack sites showed a significant clustered pattern within trees. Attack sites were aggregated towards the lower and middle bole, and on the south-facing side of trees. This pattern has been seen in other insects, including wood borers, and is potentially related to differences in temperature. These patterns of ovipositional behaviour in outbreak situations have implications forE.rufulusresource partitioning and facultative intraguild predation among larvae.