DISTRIBUTION AND ABUNDANCE OF ENGRAVER BEETLES (SCOLYTIDAE, IPS SPECIES) ON MONTEREY PINES INFECTED WITH PITCH CANKER

Pitch canker, caused by Fusarium subglutinans (Wollenw. and Reink.) Nelson, Toussoun, and Marasas, a pine pathogen recently indentified in California, may increase the distribution and abundance of Ips spp. on Monterey pines in Santa Cruz Co., CA. In all pine stands, Ips spp. tunneled into healthy branches and boles. Ips mexicanus (Hopkins) was the most abundant engraver beetle observed, followed by I. paraconfusus Lanier; I. plastographus (LeConte) was rare. Ips mexicanus was routinely captured in traps baited with racemic I. paraconfusus pheromone. During the winter, I. mexicanus excavated mass feeding cavities in shade-suppressed branches. In uninfected stands, 3% of the trees and only 0.3% of the branches were mass-attacked. In severely infected stands, 47% of the top one-third of the trees, 3% of all branches, and 91% of the branches declining due to infection by F. subglutinans were mass-attacked by Ips spp. On pitch canker-infected trees, I. mexicanus attacked cones and stems < 1 cm in diameter. Sixty percent of the attacks on logs occurred inside or within 5 cm of the area covered with pitch canker-induced resin. When confined with logs, 45% of I. paraconfusus tunneled in or near pitch canker-induced resinous areas, 21% near fresh chisel wounds, and 19% near resinous material produced by the Sequoia pitch moth, Synanthedon sequoiae (Hy. Edwards).