Response of the pine engraver, Ips pini (Say) (Coleoptera: Scolytidae), to conophthorin and other angiosperm bark volatiles in the avoidance of non-hosts
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.