Canadian Forest Service Publications
Unsaturated cuticular hydrocarbons enhance responses to sex pheromone in spruce budworm, Choristoneura fumiferana. 2017. Silk, P.J.; Eveleigh, E.S.; Roscoe, L.; Burgess, K.; Weatherby, S.; Leclair, G.; Mayo, P.; Brophy, M. Journal of Chemical Ecology 43:753–762.
Issued by: Atlantic Forestry Centre
Catalog ID: 38964
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The primary sex pheromone components of the female spruce budworm, Choristoneura fumiferana (Clem.) (Lepidoptera: Tortricidae), are (E)- and (Z)-11-tetradecenal, produced in 95:5 ratio. However, male flight responses to calling females in a wind tunnel were faster and maintained longer than responses to any synthetic aldehyde blend. Analyses of cuticular extracts from spruce budworm adults revealed series of n-alkanes and n-monoalkenes with predominantly odd numbers of carbon atoms from C23- C29 in both sexes. (Z,Z,Z)-3,6,9-tricosatriene and (Z,Z,Z)-3,6,9-pentacosatriene were identified only in cuticular extracts from females. Pheromonally naïve males showed wing fanning and circling responses to forewing scales from females but not to scales from males. Males also exhibited the same strong responses to scales excised from pharate females, indicating that the pheromone components are produced by females prior to emergence. (Z)-11-hexadecenal and (Z)-5-tricosene enhanced male responses to the primary sex pheromone aldehydes in wind tunnel bioassays, including higher proportions of in-flight and copulatory responses by males and increased time on the source. Addition of (Z,Z,Z)-3,6,9-tricosatriene to the 95/5 blend of (E)- and (Z)-11-tetradecenal released close-range copulatory responses including abdomen curling on treated septa. We propose that the sex pheromone blend of C. fumiferana is composed of the 95/5 blend of (E)- and (Z)-11-tetradecenal as primary components, with (Z)-11-hexadecenal, (Z)-5-tricosene and (Z,Z,Z)-3,6,9-tricosatriene fulfilling secondary roles in orientation and close-range courtship.
Plain Language Summary
Sex pheromones (odors) are used primarily by female insects to attract potential mates. The two main chemical components of the spruce budworm sex pheromone have been known for some time, but a synthetic blend of these components did not elicit the same flight responses in males as that of naturally calling females, indicating that several components were still missing from the known blend. In this paper, we analyzed adult spruce budworm body waxes and identified a number of additional compounds that, together with the main components, elicited behaviors in males that were closer to those elicited when males were exposed to naturally calling females. Thus, we now report a more complete pheromone blend, consisting of four components. Through bioassays, we also report that that the primary pheromone components are produced by adult females prior to emergence from the pupal stage. This new information provides a better understanding of the sex pheromone chemistry of this pest insect and, potentially, a better tool for population intervention at low densities (i.e., keeping populations from reaching outbreak levels).