Evaluation of semiochemicals potentially synergistic to α-pinene for trapping the larger European pine shoot beetle, Tomicus piniperda (Col., Scolytidae)

Abstract:  The pine shoot beetle, Tomicus piniperda (L.) (Col., Scolytidae) is an exotic pest of pine, Pinus spp., in North America. It is attracted strongly to host volatiles (±)- α -pinene, (+)-3-carene, and α -terpinolene. Attraction to insect-produced compounds is less clear. Other potential attractants include trans -verbenol, myrtenol, myrtenal, nonanal and α -pinene oxide. We conducted a series of field experiments to determine if any of these compounds would increase attraction of T. piniperda to α -pinene, either individually or in various combinations. None of the individual compounds increased attraction. Although several combinations that included trans -verbenol, nonanal, myrtenol, or myrtenal increased attraction, results were variable between experiments.     

Monoterpenes governing host selection in the bark beetles Hylurgops palliatus and Tomicus piniperda

Under field conditions, both bark beetles, Hylurgops palliatus Gyll. and Tomicus piniperda L. (Col., Scolytidae) preferred flight barrier traps baited with ethanol and oleoresin of their favoured host, Picea abies L., and Pinus sylvestris L., respectively, compared to traps baited with ethanol and various monoterpenes. However, replacing the host-specific oleoresin with -pinene and the pine-characteristic terpinolene enhanced trap catches of both species. Response of H. palliatus increased with myrtenol, but decreased with (+)-trans-verbenol, while T. piniperda was attracted by both terpene alcohols.

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Zusammenfassung Die Lockwirkung wirtsspezifischer Terpenmuster auf die sekundären Rindenbrüter Hylurgops palliatus und Tomicus piniperda wird im Freiland untersucht. Beide Arten fliegen bevorzugt Fallen an, die mit Ethanol und dem Rohharz ihrer Wirtsbäume, Picea abies bzw. Pinus sylvestris, beködert sind. Der Ersatz der Rohharze durch eine Mischung aus -Pinen und dem für Kiefernharz charakteristischen Terpinolen erhöht die Fangzahlen beider Arten deutlich. Die Präferenzen für Monoterpene deuten unterschiedlich enge Wirtsbindungen an: Bei breitem Wirtsspektrum bevorzugt H. palliatus wenig spezifische Terpene und hohe Ethanol-Konzentrationen, der zur Monophagie an Frischholz neigende Waldgärtner T. piniperda jedoch geringe Ethanol-Konzentrationen und spezifische Terpenkombinationen. H. palliatus wird von dem Terpenalkohol (-)-Myrtenol deutlich angelockt, während das von aggressiven Scolytiden bekannte Pheromon (+)-trans-Verbenol seinen Anflug im Gegensatz zu T. piniperda zu hemmen scheint.

     

Antimicrobial and anti‐inflammatory activity of five Taxandria fragrans oils in vitro

The antimicrobial activity of five samples of Taxandria fragrans essential oil was evaluated against a range of Gram‐positive (n= 26) and Gram‐negative bacteria (n= 39) and yeasts (n= 10). The majority of organisms were inhibited and/or killed at concentrations ranging from 0.06–4.0% v/v. Geometric means of MIC were lowest for oil Z (0.77% v/v), followed by oils X (0.86%), C (1.12%), A (1.23%) and B (1.24%). Despite differences in susceptibility data between oils, oils A and X did not differ when tested at 2% v/v in a time kill assay against Staphylococcus aureus. Cytotoxicity assays using peripheral blood mononuclear cells demonstrated that T. fragrans oil was cytotoxic at 0.004% v/v but not at 0.002%. Exposure to one or more of the oils at concentrations of ≤0.002% v/v resulted in a dose responsive reduction in the production of proinflammatory cytokines IL‐6 and TNF‐α, regulatory cytokine IL‐10, Th1 cytokine IFN‐γ and Th2 cytokines IL‐5 and IL‐13 by PHA stimulated mononuclear cells. Oil B inhibited the production of all cytokines except IL‐10, oil X inhibited TNF‐α, IL‐6 and IL‐10, oil A inhibited TNF‐α and IL‐6, oil C inhibited IL‐5 and IL‐6 and oil Z inhibited IL‐13 only. IL‐6 production was significantly inhibited by the most oils (A, B, C and X), followed by TNF‐α (oils A, B and X). In conclusion, T. fragrans oil showed both antimicrobial and anti‐inflammatory activity in vitro, however, the clinical relevance of this remains to be determined.     

Influence of sex,maturity and host substances on pheromones in the guts of the bark beetles, Ips paraconfusus and Dendroctonus brevicomis

Pheromones and metabolites of host (ponderosa pine) compounds were found in association with the hindgut of both naturally fed and of non-fed, host vapour-exposed bark beetles, Ips paraconfusus and Dendroctonus brevicomis. Much smaller amounts were found in the corresponding heads and mid guts. Sex-specific differences in content of pheromones were observed as in earlier studies. Exposure of I. paraconfusus to vapours of a pheromone component, ipsenol and other monoterpene alcohols resulted in their accumulation in the hindgut but relatively very low amounts in the head. The possible sites of pheromone biosynthesis are discussed. Exposure of male I. paraconfusus to vapours of host compounds, myrcene and α-pinene, revealed that immature adults do not produce the pheromone components, ipsenol and ipsdienol, as mature adults do while both immature and mature sexes produced another pheromone component, cis-verbenol, as well as trans-verbenol and myrtenol. Immature D. brevicomis adults did not contain pheromones until their exposure to vapours of (?)-α-pinene which caused production of trans-verbenol but only about 10% that of mature adults treated similarly. Verbenone, a male-produced inhibitory pheromone of D. brevicomis, apparently was not synthesized from (?)-α-pinene in females nor was its synthesis in males enhanced by exposure to this host compound.     

Aggregation response of European engraver beetles of the genus Ips mediated by terpenoid pheromones

Upon exposure to vapours of the host tree's monoterpene (–)--pinene, Ips acuminatus produces the terpene alcohol cis-verbenol which, besides ipsdienol and ipsenol, is a component of its aggregation pheromone. I. cembrae transforms the same monoterpene predominantly into myrtenol and trans-verbenol but little into cis-verbenol, which interrupts pheromone response under field conditions.On the other hand, I. cembrae releases, upon feeding in the bark, the terpene alcohol amitinol in major amounts. Amitinol significantly enhances field response to the aggregation pheromone that also includes ipsdienol, ipsenol, and 3-methyl-3-buten-1-ol. However, amitinol reduces pheromone response in I. acuminatus and I. erosus. Also, males of I. sexdentatus release amitinol which appears to increase response to its attractive principle pheromone component, racemic ipsdienol. There is some evidence that present knowledge of the chemical communication systems among European Ips spp. still lacks satisfactory explanation of the naturally occuring aggregation en masse, perhaps with the exception of I. erosus and I. typographus.