Dendroentomological evidence associated with an outbreak of the native wood-boring beetleEnaphalodes rufulus

Abstract

An outbreak of Enaphalodes rufulus Haldeman, a North American wood-boring cerambycid beetle, appears to be a major contributing factor to a recent Quercus rubra L. mortality event. The objectives of this research were to investigate the historical activity and within-tree distributions of E. rufulus by using scars formed by larval feeding in the cambium and xylem. Scars were counted and dated in fifteen 63- to 88-year-old northern red oaks; five in each of three infestation classes (low, moderate, and high). There were significantly fewer scars noted in low infestation trees than in trees with high infestations, and moderately infested trees showed intermediate scarring. There were significant differences in the date of the first xylem scar with initial scars occurring in 1980 in low infestation trees, 1952 in moderate, and 1940 in high. The number of xylem scars present varied significantly at different heights on the tree bole, but no differences were found based on tree aspect. This research provides evidence that an outbreak of red oak borer has not occurred before in these trees, beetles have not undergone recent population oscillations, trees that are currently highly infested have been infested over a longer period of time and at higher densities than low infestation trees, and there are distinctive within-tree larval distributions.