Response of Invasive Longhorn Beetles (Coleoptera: Lamiinae) to Known Cerambycid Aggregation-Sex Pheromones in the Puna District of Hawaii Island

The Queensland longhorn borer (QLB; Acalolepta aesthetica [Olliff 1890]; Coleoptera: Cerambycidae: Lamiinae: Monochamini) and plumeria long- horn borer (PLB; Lagocheirus obsoletus [Thomson 1778] = Lagocheirus undatus [Voet 1778]; Coleoptera: Cerambycidae: Lamiinae: Acanthocini) are invasive longhorn beetle species that have become established on the island of Hawaii. Both QLB and PLB are polyphagous. Known hosts of QLB include cacao, citrus, kukui, and breadfruit in Hawaii, and QLB are known to attack live, healthy trees. Currently the beetle occurs in the Puna district of the island, but its range is expanding. PLB is a pest of plumeria and other ornamental plants throughout the state of Hawaii and elsewhere. As a first step towards developing a monitoring tool for these invasive beetles, we tested four known aggregation-sex pheromones of cerambycids in this subfamily—monochamol, fuscumol acetate, fuscumol, and geranylacetone—that have proven effective for attracting more than 30 lamiine species in different areas of the world. When tested in panel traps, these compounds individually and in a blend attracted 9 QLB total, which was not significantly different than the 5 QLB captured in solvent control traps. In contrast, traps baited with one of the tested compounds, fuscumol acetate, captured significantly more PLB than solvent blank control traps. We discuss future research directions for developing attractants using chemical ecology approaches to monitor QLB and PLB

Fungal Volatiles Can Act as Carbon Sources and Semiochemicals to Mediate Interspecific Interactions Among Bark Beetle-Associated Fungal Symbionts.

Mountain pine beetle (Dendroctonus ponderosae) has killed millions of hectares of pine forests in western North America. Beetle success is dependent upon a community of symbiotic fungi comprised of Grosmannia clavigera, Ophiostoma montium, and Leptographium longiclavatum. Factors regulating the dynamics of this community during pine infection are largely unknown. However, fungal volatile organic compounds (FVOCs) help shape fungal interactions in model and agricultural systems and thus may be important drivers of interactions among bark beetle-associated fungi. We investigated whether FVOCs can mediate interspecific interactions among mountain pine beetle's fungal symbionts by affecting fungal growth and reproduction. Headspace volatiles were collected and identified to determine species-specific volatile profiles. Interspecific effects of volatiles on fungal growth and conidia production were assessed by pairing physically-separated fungal cultures grown either on a carbon-poor or -rich substrate, inside a shared-headspace environment. Fungal VOC profiles differed by species and influenced the growth and/or conidia production of the other species. Further, our results showed that FVOCs can be used as carbon sources for fungi developing on carbon-poor substrates. This is the first report demonstrating that FVOCs can drive interactions among bark beetle fungal symbionts, and thus are important factors in beetle attack success

Mean (± s.e.) differences in culture area (mm², A) and conidia density (conidia per mm²; B) among fungal symbionts, <i>Grosmannia clavigera</i> (Grcl), <i>Ophiostoma montium</i> (Opmo), and <i>Leptographium longiclavatum</i> (Lelo), of mountain pine beetle (<i>Dendroctonus ponderosae</i>) for controls of the staggered-growth experiment.

<p>Bars with different letters are statistically different as indicated by Tukey Honest Significant Difference tests.</p

The composition of headspace volatile (rows) profiles from four-day old <i>Ophiostom montium</i> (Opmo), <i>Leptographium longiclavatum</i> (Lelo), and <i>Grosmannia clavigera</i> (Grcl) cultures.

<p>Cells contain the percentage of each volatile out of the total concentration of all detected volatiles by fungus. The dendrogram shows similarities among fungi based on volatile profile compositions as indicated by hierarchical clustering.</p

Mean (± s.e.) differences in culture area (mm², A) and conidia density (conidia per mm²; B) among fungal symbionts, <i>Grosmannia clavigera</i> (Grcl), <i>Ophiostoma montium</i> (Opmo), and <i>Leptographium longiclavatum</i> (Lelo), of mountain pine beetle (<i>Dendroctonus ponderosae</i>) for controls of the concurrent-growth experiment.

<p>Bars with different letters are statistically different as indicated by Tukey Honest Significant Difference tests.</p

NMDS results showing the separation of <i>Ophiostoma montium</i> (Opmo), <i>Leptographium longiclavatum</i> (Lelo), and <i>Grosmannia clavigera</i> (Grcl) based on concentrations (ng mm^-2) of nine headspace volatiles: acetoin (ATN), ethyl acetate (ETA), <i>cis</i>-grandisol (GRD), isobutanol (IBA), isoamyl acetate (IAA), 2-methyl-1-butanol (2MB), 3-methyl-1-butanol (3MB), phenethyl acetate (PEAC), and phenethyl alcohol (PEA).

<p>Black ellipses indicate 95% confidence intervals around cluster centroids.</p

Results of concurrent-growth experiment showing mean (± s.e.) growth (mm²; left panels) and conidia density (conidia mm^-2; right panels) responses to headspace volatiles of the other fungi in species-pairing treatments and non-inoculated agar controls for <i>Grosmannia clavigera</i> (Grcl; A, B), <i>Ophiostoma montium</i> (Opmo, C, D), and <i>Leptographium longiclavatum</i> (Lelo; E, F).

<p>Bars with different letters are statistically different as indicated by Tukey Honest Significant Difference tests.</p

Results of staggered-growth experiment showing mean (± s.e.) growth (mm²; left panels) and conidia density (conidia mm^-2; right panels) responses to headspace volatiles of the other fungi in species-pairing treatments and non-inoculated agar controls for <i>Grosmannia clavigera</i> (Grcl; A, B), <i>Ophiostoma montium</i> (Opmo, C, D), and <i>Leptographium longiclavatum</i> (Lelo; E, F).

<p>Bars with different letters are statistically different as indicated by Tukey Honest Significant Difference tests.</p

Mean concentrations (ng mm^-2) of detected headspace volatiles from four-day old cultures of mountain pine beetle (<i>Dendroctonus ponderosae</i>)-symbiotic fungi: <i>Grosmannia clavigera</i>, <i>Ophiostoma montium</i>, and <i>Leptographium longiclavatum</i>.

<p>ANOVA results for among-species differences in mean concentrations for each compound. Means with different letter superscripts are significantly different as indicated by Tukey Honest Significant Difference tests. Compounds not detected in headspace collections of a given fungus are indicated with “ND.”</p

Mean (± s.e.) growth (mm²) responses of <i>Grosmannia clavigera</i> (Grcl; A), <i>Ophiostoma montium</i> (Opmo, B), and <i>Leptographium longiclavatum</i> (Lelo; C) on yeast nutrient base agar and exposed to headspace volatiles of other fungi in species-pairing treatments and non-inoculated agar controls.

<p>Bars with different letters are statistically different as indicated by Tukey Honest Significant Difference tests.</p