A host monoterpene influences Ips typographus (Coleoptera: Curculionidae, Scolytinae) responses to its aggregation pheromone

Abstract

1 Host tree terpenes can influence attraction of conifer-infesting bark beetles to their aggregation pheromones, and both synergistic and inhibitory effects have been reported. 2 We tested a gradient of ratios of ( -)-␣ -pinene, the predominant monoterpene in Norway spruce, to the pheromone of Ips typographus , a major pest of Norway spruce. 3 Attraction of I. typographus increased as the release rate of ( -)-␣ -pinene increased. The two highest ( -)-␣ -pinene : pheromone ratios (526 : 1 and 2595 : 1) attracted twice as many I. typographus as pheromone alone, whereas low to intermediate ratios (56 : 1, 274 : 1) did not differ from pheromone alone. 4 Our results are in agreement with a proposed model, which suggests that bark beetles display unique response profiles to host terpenes depending on the physiological condition of the host trees that they typically colonize. Ips typographus , which is an aggressive species capable of colonizing and killing healthy trees, showed an increased attraction to monoterpene : pheromone ratios, and this may be high enough to inhibit attraction of less aggressive beetle species typically colonizing dead, dying or stressed trees. 5 Attraction of associates of I. typographus was also modified by ( -)-␣ -pinene. Ips duplicatus , a competitor of I. typographus , showed increased attraction to the pheromone of I. typographus across all concentrations of ( -)-␣ -pinene.

Semiochemicals in the Natural History of Southern Pine Beetle Dendroctonus frontalis Zimmermann and Their Role in Pest Management

“…It may also communicate the defensive capabilities of the potential host, as has been suggested to occur for less aggressive bark beetle species that are attracted to modest concentrations of host monoterpenes but repelled by higher ones (Erbilgin et al, 2003). Host monoterpenes are toxic to bark beetles (Cook and Hain, 1988;Everaerts et al, 2012), and presumably airborne resin terpene concentrations that exceed a certain threshold should signal a host whose defensive response may be greater than can be withstood by the host-seeking species (Erbilgin et al, 2007b). The very high rates of turpentine odours preferred by D. frontalis are simultaneously inhibitory to their significant competitor I. avulsus (Billings, 1985).…”

Electrophysiological and behavioural responses of Ips typographus (L.) to trans-4-thujanol—a host tree volatile compound

“…Volatiles released by the host plant play an important role when pioneer bark beetles search for a host tree (Andersson 2012;Erbilgin et al 2007). Ips typographus can perceive at least 18 compounds emitted by its host plant (Kalinová et al 2014).…”

“…Byers 1989;Landolt and Phillips 1997). For I. typographus for example, α-pinene-the predominant monoterpene in Norway spruce-enhances the attractiveness of the aggregation pheromone (Erbilgin et al 2007;Jakuš and Blaženec 2003). Conversely, 1,8-cineole acts as an antagonist inhibiting attraction to the aggregation pheromone (Andersson et al 2010).…”

Peripheral modulation of pheromone response by inhibitory host compound in a beetle

“…Verbenone synergizes the inhibitory effect of NHVs in I. typographus (Zhang and Schlyter, 2003) and is used as a negative cue also by several other bark beetle species (Lindgren and Miller, 2002;Schlyter and Birgersson, 1999). Very little is known about the behavioral relevance of host monoterpenes in I. typographus (Erbilgin et al, 2007) or the host phenolics (Faccoli and Schlyter, 2007) and other less volatile host compounds, such as sesquiterpenes.…”