Attraction of the twolined chestnut borer (Coleoptera: Buprestidae) to scarlet oaks infected with chestnut blight fungus

Chestnut blight fungus, Cryphonectria (Endothia) parasitica, causes bark and wood deformity to the lower bole of scarlet oak, Quercus coccinea L., but does not kill the tree. We tested the hypothesis that C. Parasitica infection stresses the tree and predisposes it to attack by the twolined chestnut borer, Agrilus bilineatus (Weber). Scarlet oaks with obvious disease symptoms attracted significantly more A. Bilineatus, cerambycids, and scolytids than did apparently healthy trees. However, only 9 of 21 diseased trees were successfully colonized. Total nitrogen and tannin concentrations of the phloem did not differ significantly between diseased and control trees; however, phenolic concentrations were significantly higher in the phloem of diseased trees that were colonized by borers. Total carbohydrate concentrations of xylem and phloem in July did not differ significantly between diseased and control trees, even in those diseased trees that were colonized. However, starch concentrations of the outer sapwood were slightly lower in all diseased trees. This tree decline complex is unusual in that the apparent predisposing stress, C. Parasitica, did not reduce radial growth or total carbohydrates, which are generally regarded as indicators of tree vigor.