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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]

A long-standing controversy questions whether foraging bark beetles assess the suitability of individual host trees using cues at close range while flying or engage in random landing followed by contact assessment. In most cases, visual discrimination mechanisms are ignored. We show that pheromone-responding mountain pine beetles (MPB), Dendroctonus ponderosae Hopkins (Coleoptera: Scolytidae), can visually discriminate between ‘host’ (black) and ‘non-host’ (white) traps arranged in small clusters, in the absence of additional host olfactory information, and that males (but not females) demonstrate a greater preference for combined host visual and olfactory cues. However, white, non-host traps baited with a host volatile were as attractive as unbaited, black host traps. Our results support the hypotheses that when deciding to land, the MPBs integrate visual and olfactory information and can process cues in both sensory modes at relatively close range (≤2 m). Thus, host selection mechanisms in this species are unlikely to be random with respect to either sensory mode. [ABSTRACT FROM AUTHOR]

We conducted four behavioral choice tests in stands of mature lodgepole pine in British Columbia, from 1988 to 1991, to determine the dose-dependent responses of Orthotomicus latidens (LeConte) and Ips pini (Say) to their respective pheromones. Dose-dependent responses were exhibited by I. pini to (±)-ipsdienol and lanierone, with trap catches directly proportional to pheromone release rates. We found differences in sex ratio of I. pini in their responses to ipsdienol but not lanierone. There was no dose-dependent response exhibited by O. latidens to its pheromone, (±)-ipsenol, with or without the presence of the host kairomone, (-)-β-phellandrene. The bark beetle predator, Enoclerus lecontei (Wolcott), showed a dose-dependent response to lanierone. Thanasimus undatulus (Say) was attracted to ipsenol in a dose-dependent fashion only when traps were also baited with β-phellandrene. Neither T undatulus nor E. sphegeus (F.) exhibited dose-dependent responses to ipsdienol. [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]

We investigated the hypothesis that interspecific interactions between the spruce beetle, Dendroctonus rufipennis Kirby, and 2 secondary species, Ips tridens Mannerheim and Dryocoetes affaber Mannerheim, adversely affect species beetle progeny production and survival. In field experiments in the British Columbia interior, attack by the secondary species was induced by placing pheromone baits on felled trees just after spruce beetle attack. Spruce beetle attack densities, gallery length per square meter, and progeny densities were significantly reduced in trees that were baited with D. affaber pheromones or D. affaber and I. tridens pheromones. Resource exploitation and synomonal interference with subsequent spruce beetle attacks were the primary competitive mechanisms. No evidence for direct interference was found. Because the impact of the secondary species was not pronounced, semiochemical-induced competitive displacement of the spruce beetle after it has established would not be practical for retarding the development of, or suppressing, beetle outbreaks. [ABSTRACT FROM PUBLISHER]