Protection of lodgepole pine from attack by the mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Scolytidae) using high doses of verbenone in combination with nonhost bark volatiles

Abstract

We evaluated the antiaggregation pheromone verbenone at low and high doses alone and with a seven-component repellent blend of nonhost angiosperm bark volatiles (NHVs) for their ability to deter attack by the mountain pine beetle, Dendroctonus ponderosae Hopkins. Release devices containing antiaggregants were deployed at 16 points on a 10-m grid in 40 × 40-m plots near Williams Lake, B.C. in June 2001. In 10 control plots with no antiaggregants, single pheromone-baited trees, at the plot centre were all mass-attacked by the mountain pine beetle by early October, as were 26.6% of the 432 lodgepole pines within the boundaries of the plots. In contrast, in plots treated with a high dose of verbenone plus NHVs, two of the central, pheromone-baited trees escaped any attack whatsoever, four of 10 plots had no surrounding trees attacked and only 2.1% of the total of 523 surrounding trees were mass-attacked. Density of attacked and mass-attacked trees was highest within 5 m of the central baited tree in all treatments, indicating that those beetles that breached the antiaggregant grid were then drawn toward the baited tree. Operational efficacy should thus be improved in the absence of baited trees within a treated area. We conclude that high-dose verbenone plus NHV treatments could be implemented operationally as a minor component of an integrated pest management strategy for large infestations, particularly in a push-pull tactic in which beetles are pushed from one area by the antiaggregant treatment and drawn into another with attractive baits. However, the principal use would be in the short-term protection of small, high-value stands or stands of high ecological or social value. Key words: Coleoptera, Scolytidae, Dendroctonus ponderosae, chemical ecology, verbenone, pest management