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1. There has been a long-standing pre-occupation with how phytophagous insects use olfactory cues to discriminate hosts from non-hosts. Foragers, however, should use whatever cues are accurate and easily assessed, including visual cues. 2. It was hypothesised that three bark beetles, the mountain pine beetle (MPB), Dendroctonus ponderosae Hopkins, the Douglas-fir beetle (DFB), D. pseudotsugae Hopkins, and the western balsam bark beetle (WBBB), Dryocoetes confusus Swaine, integrate visual and olfactory information to avoid non-host angiosperms (e.g. paper birch, trembling aspen), that differ in visual and semiochemical profile from their respective host conifers (lodgepole pine, Douglas-fir, interior fir), and tested this hypothesis in a series of field trapping experiments. 3. All three species avoided attractant-baited, white (non-host simulating) multiple-funnel traps, and preferred attractant-baited black (host-simulating) traps. In experiments combining white, non-host traps with non-host angiosperm volatiles, bark beetles were repelled by these stimuli in an additive or redundant manner, confirming that these species could integrate visual and olfactory information to avoid non-host angiosperms while flying. 4. When antiaggregation pheromones were released from white traps, the DFB and MPB were repelled in an additive-redundant manner, suggesting that beetles can integrate diverse and potentially anomalous stimuli. 5. The MPB demonstrated the most consistent visual preferences, suggesting that it may be more of a ‘visual specialist’ than the DFB or WBBB, for which visual responses may be more contingent on olfactory inputs. [ABSTRACT FROM AUTHOR]

Hybrid poplar clones show varying levels of attack by Cryptorhynchus lapathi (L.), a wood-boring weevil. We studied differences in olfactory and feeding behavior among four different hybrid poplars in a series of laboratory bioassays. Weevils did not discriminate between resistant and susceptible clones based on olfaction in pitfall bioassays or antennal responses but did discriminate against the most resistant hybrid, NM 6 (P. nigra L. × P. maximowiczii Henry), in choice and no-choice paired-twig feeding bioassays. In addition, the susceptible hybrid, TN 302-9 (P. trichocarpa Torrey and Gray × P. nigra), was preferred for feeding over Salix scouleriana Barratt ex Hooker, a preferred host in the wild. We conclude that resistance among hybrid poplars is in part based on antixenotic cues before oviposition. [ABSTRACT FROM AUTHOR]

1 Synthetic blends of bole and foliage volatiles of four sympatric species of conifers were released from pheromone-baited multiple-funnel traps to determine if three species of tree-killing bark beetles (Coleoptera: Scolytidae): (i) exhibited primary attraction to volatiles of their hosts and (ii) discriminated among volatiles of four sympatric species of host and nonhost conifers. 2 Bole and foliage volatiles from Douglas-fir, Pseudotsuga menziesii (Mirb.) Franco, increased the attraction of coastal and interior Douglas-fir beetles, Dendroctonus pseudotsugae Hopkins, to pheromone-baited traps. Primary attraction to bole volatiles was observed in interior D. pseudotsugae. Beetles were significantly less attracted to the pheromone bait when it was combined with volatiles of lodgepole pine, Pinus contorta var. latifolia Engelm. or interior fir, Abies lasiocarpa × bifolia. 3 The monoterpene myrcene synergized attraction of mountain pine beetles, Dendroctonus ponderosae Hopkins, to their aggregation pheromones, but there was no evidence of primary attraction to host volatiles or discrimination among volatiles from the four conifers. 4 There was significant primary attraction of the spruce beetle, Dendroctonus rufipennis Kirby, to bole and foliage volatiles of interior spruce, Picea engelmannii × glauca, but beetles did not discriminate among volatiles of four sympatric conifers when they were combined with pheromone baits. 5 Our results indicate that host volatiles act as kairomones to aid pioneer Douglas-fir beetles and spruce beetles in host location by primary attraction, and that their role as synergists to aggregation pheromones is significant. For the mountain pine beetle, we conclude that random landing and close range acceptance or rejection of potential hosts would occur in the absence of aggregation pheromones emanating from a tree under attack. [ABSTRACT FROM AUTHOR]

Abstract 1 Seventeen non-host angiosperm bark volatiles, seven of which are antennally active to Ips pini (Say), the pine engraver (PE), were tested for their ability to disrupt the response of the PE to pheromone-baited traps. 2 Four green leaf volatiles (GLVs) were tested [1-hexanol (Z)-3-hexen-1-ol, hexanal, and (E)-2-hexenal]. None had any disruptive effect singly, as a group or in all possible blends based on functional groups, despite the fact that the two aldehydes were antennally active. These compounds may have, in some instances, actually masked the disruptive effect of other compounds. The PE thus differs in its response from other Scolytidae, including other Ips spp. 3 Eight non-host volatiles that were antennally active to other bark beetles, but not to PEs, had no disruptive effect, validating the use of coupled gas chromatographic-electroantennographic detection analyses to detect compounds with potential behavioural activity. 4 The bicyclic spiroacetal conophthorin, (E)-7-methyl-1,6-dioxaspiro[4.5]decane, was disruptive when tested alone. When blends of two aldehydes [salicylaldehyde and nonanal] plus an alcohol and a phenol [benzyl alcohol and guaiacol] were combined with conophthorin, an enhanced disruptive effect was revealed. No single compound, other than conophthorin, disrupted the pheromone-positive response and no blend that did not contain conophthorin was consistently disruptive to both sexes. Conophthorin seems to be a critical component in the non-host angiosperm message for I. pini during its host selection phase. 5 Combination of the repellent synomones, verbenone and ipsenol, with the five disruptive non-host volatiles may provide a potent treatment to protect trees, logs or stands from attack by the PE. [ABSTRACT FROM AUTHOR]