Date Published: September 20, 2013
Publisher: Public Library of Science
Author(s): Juliana Jaramillo, Baldwyn Torto, Dickson Mwenda, Armin Troeger, Christian Borgemeister, Hans-Michael Poehling, Wittko Francke, Frederic Marion-Poll.
Unanswered key questions in bark beetle-plant interactions concern host finding in species attacking angiosperms in tropical zones and whether management strategies based on chemical signaling used for their conifer-attacking temperate relatives may also be applied in the tropics. We hypothesized that there should be a common link in chemical signaling mediating host location by these Scolytids. Using laboratory behavioral assays and chemical analysis we demonstrate that the yellow-orange exocarp stage of coffee berries, which attracts the coffee berry borer, releases relatively high amounts of volatiles including conophthorin, chalcogran, frontalin and sulcatone that are typically associated with Scolytinae chemical ecology. The green stage of the berry produces a much less complex bouquet containing small amounts of conophthorin but no other compounds known as bark beetle semiochemicals. In behavioral assays, the coffee berry borer was attracted to the spiroacetals conophthorin and chalcogran, but avoided the monoterpenes verbenone and α-pinene, demonstrating that, as in their conifer-attacking relatives in temperate zones, the use of host and non-host volatiles is also critical in host finding by tropical species. We speculate that microorganisms formed a common basis for the establishment of crucial chemical signals comprising inter- and intraspecific communication systems in both temperate- and tropical-occurring bark beetles attacking gymnosperms and angiosperms.
Phytophagous insects recognize specific olfactory signals in order to find their hosts against the ‘background noise’ caused by environmental odours This specificity in olfactory signaling is typically defined by its quantity and/or quality, which in turn is governed by relative proportions of components in the signal . As a result of these interactions, some plants have evolved to mimic the odor bouquet of certain insects to cause avoidance behaviour in herbivores , as demonstrated for bark beetles whose sensory detection system allows them not only to detect host volatiles, but also to avoid non-host volatiles –.