trans-Verbenol and Alpha-Pinene: Their Utility in Manipulation of the Mountain Pine Beetle1

Abstract

Synthetic trans-verbenol containing 6% cis-verbenol and 1% unknowns combined with alpha-pinene was highly attractive to in-flight mountain pine beetle, Dendroctonus ponderosae Hopkins. Alpha-pinene was the most active of the terpenes tested with trans-verbenol. Myrcene showed intermediate activity, while limonene and 3-carene apparently were ineffective in eliciting a response. As behavior-regulating chemicals, trans-verbenol and alphapinene were effective in manipulating the host selection patterns of D. ponderosae. When 725 mature white pines, distributed over eight 40-acre plots in northern Idaho, were baited with the 2 materials, 133 or 18% were attacked heavily and subsequently killed. Beetle attacks were noted on an additional 15% of the baited trees, but these were aborted without tree mortality. Prior to baiting, all trees were sprayed to a height of about 20 ft with a 2.3% solution of lindane. The mortality of sprayed trees suggested that lindane was not effective under the conditions of this study. Only 21 of the estimated 7200 unbaited mature pines within the boundaries of the study plots were mass attacked, and 11 of these trees were within 10 to 15 ft of baited mass-attacked trees. Paperboard cylinders, about 8 ft × 10 in., covered with a tacky substance and baited with trans-verbenol and alpha-pinene appeared effective as a means of deadtrapping D. ponderosae. An abnormally high attack density could not be induced on a white pine baited with a massive amount of trans-verbenol and alpha-pinene.