REDUNDANCY IN THE SEMIOCHEMICAL MESSAGE REQUIRED TO INDUCE ATTACK ON LODGEPOLE PINES BY THE MOUNTAIN PINE-BEETLE, DENDROCTONUS-PONDEROSAE HOPKINS (COLEOPTERA, SCOLYTIDAE)

Baited tree experiments confirmed the hypothesis that frontal in is a multifunctional pheromone that can induce the mountain pine beetle, Dendroctonus ponderosae Hopkins, to aggregate on and mass-attack lodgepole pine, Pinus contorta var. latifolia Engelmann. A re-examination was undertaken of the role of four known semiochem-icals, myrcene, trans-verbenol, exo-brevicomin, and frontal in, tested as tree baits alone (with the exception of myrcene) and in all possible combinations. There was considerable redundancy evident in the semiochemical signal. For example, myrcene + fron-talin and fram-verbenol + exo-brevicomin induced attack on baited trees at similar levels of intensity. The results suggest that beetles of either sex could initiate a mass attack. During the most attractive phase of host colonization, redundancy in the semio-chemical signal could act as a fail-safe mechanism to ensure perception of and response to odors from an attacked tree. In addition the standard, commercial, tree bait containing myrcene, trans-verbenol, and exo-brevicomin might be modified by deleting myrcene, making a more acceptable and cost-effective operational bait. © 1990, Entomological Society of Canada. All rights reserved.