Green leaf volatiles (GLVs) function as host attractants, pheromone synergists, or sexual kairomones for a number of coleopteran folivores. Hence, we focused on host GLVs to determine if they were attractive to adults of the emerald ash borer, Agrilus planipennis (Coleoptera: Buprestidae), which feeds on ash (Fraxinus) foliage. Eight GLVs were identified by chromatography-electroantennogram (GC) and GC-mass spectrometry in foliar headspace volatiles collected in traps containing Super-Q from white ash, Fraxinus americana, and green ash, Fraxinus pennsylvanica, trees. GLVs in the aeration extracts elicited antennal responses from both male and female adults in gas chromatography-electroantennogram detection bioassays. Male antennae were more responsive than female antennae and showed the strongest response to (Z)-3-hexenol. Six field experiments were conducted in Canada and the USA from 2004 to 2006 to evaluate the attractiveness of candidate GLVs, in various lure combinations and dosages. Field experiments demonstrated that lures containing (Z)-3-hexenol were the most effective in increasing trap catch when placed on purple traps in open areas or along the edges of woodlots containing ash. Lures with (Z)-3-hexenol were more attractive to males than females, and dosage may be a factor determining its effectiveness.

We investigated the volatile emissions of Manchurian ash seedlings, Fraxinus mandshurica, in response to feeding by the emerald ash borer, Agrilus planipennis, and to exogenous application of methyl jasmonate (MeJA). Feeding damage by adult A. planipennis and MeJA treatment increased volatile emissions compared to unexposed controls. Although the same compounds were emitted from plants damaged by beetles and treated with MeJA, quantitative differences were found in the amounts of emissions for individual compounds. Adult virgin female A. planipennis were similarly attracted to volatiles from plants damaged by beetles and those treated with MeJA in olfactometer bioassays; males did not respond significantly to the same volatiles. Coupled gas chromatographic-electroantennogram detection (GC-EAD) revealed at least 16 antennally-active compounds from F. mandshurica, including: hexanal, (E)-2-hexenal, (Z)-3-hexen-1-ol, 3-methyl-butylaldoxime, 2-methyl-butylaldoxime, (Z)-3-hexen-1-yl acetate, hexyl acetate, (E)-β-ocimene, linalool, 4,8-dimethyl-1,3,7-nonatriene, and E,E-α-farnesene. Electroantennogram (EAG) dose-response curves using synthetic compounds revealed that females had a stronger EAG response to linalool than males; and male responses were greater to: hexanal, (E)-2-hexenal, (Z)-3-hexen-1-ol, 3-methylbutylaldoxime, 2-methyl-butylaldoxime, and hexyl acetate. These results suggest that females may use induced volatiles in long-range host finding, while their role for males is unclear. If attraction of females to these volatiles in an olfactometer is upheld by field experiments, host plant volatiles may find practical application in detection and monitoring of A. planipennis populations.

Understanding the evolutionary histories of invasive species is critical to adopt appropriate management strategies, but this process can be exceedingly complex to unravel. As illustrated in this study of the worldwide invasion of the woodwasp Sirex noctilio, population genetic analyses using coalescent-based scenario testing together with Bayesian clustering and historical records provide opportunities to address this problem. The pest spread from its native Eurasian range to the Southern Hemisphere in the 1900s and recently to Northern America, where it poses economic and potentially ecological threats to planted and native Pinus spp. To investigate the origins and pathways of invasion, samples from five continents were analysed using microsatellite and sequence data. The results of clustering analysis and scenario testing suggest that the invasion history is much more complex than previously believed, with most of the populations being admixtures resulting from independent introductions from Europe and subsequent spread among the invaded areas. Clustering analyses revealed two major source gene pools, one of which the scenario testing suggests is an as yet unsampled source. Results also shed light on the microevolutionary processes occurring during introductions, and showed that only few specimens gave rise to some of the populations. Analyses of microsatellites using clustering and scenario testing considered against historical data drastically altered our understanding of the invasion history of S. noctilio and will have important implications for the strategies employed to fight its spread. This study illustrates the value of combining clustering and ABC methods in a comprehensive framework to dissect the complex patterns of spread of global invaders.