Wednesday, December 13, 2006

Correlation of tree and stand data with red oak borer, Enaphalodes rufulus (Haldeman) (Coleoptera: Cerambycidae), population densities

Melissa K. Fierke,, Laurel J. Haavik,, and Fred M. Stephen, University of Arkansas, Department of Entomology, 319 Agriculture Building, University of Arkansas, Fayetteville, AR

Epidemic populations of red oak borer, Enaphalodes rufulus (Haldeman), a native wood-boring insect, has been implicated as a major contributor to a recent widespread oak mortality event in the Ozark National Forest of northwest Arkansas. Research objectives were to correlate individual tree data with red oak borer population density data. Sixty-nine northern red oaks, Quercus rubra L., were harvested from three general geographic areas on five topographic positions during the 2003 cohort. Five red oak borer population variables were measured using whole and partial-tree dissection: attack holes, emergence holes, phloem-feeding galleries initiated, live larvae, and previous generation galleries (red oak borer to survive and emerge throughout the life of the tree). Site and tree data included geographic area, topographic position, diameter at breast height (dbh), total tree height, height of infested bole, crown condition, number of basal emergence holes below 2 m, tree age, basal diameter, phloem width, number of sapwood (functional xylem) rings, width of sapwood, past 5 yr growth rate, 10 yr incremental growth rates back to tree establishment, and relative tree response to known historical droughts. Regression analyses indicate that geographic area, topographic position, tree age, crown condition and growth rates were correlated with population densities. Results elucidate site and tree variables associated with increased red oak borer population densities and should prove helpful in understanding factors contributing to the recent outbreak and tree mortality.

Species 1: Coleoptera Cerambycidae Enaphalodes rufulus (red oak borer)
Species 2: Fagales Fagaceae Quercus rubra (northern red oak)