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The redbay ambrosia beetle, Xyleborus glabratus, is the vector of the laurel wilt disease fungal pathogen, Raffaelea lauricola. Since the vector's initial detection in the USA in the early 2000s, laurel wilt has killed millions of redbay, Persea borbonia, trees and other members of the plant family Lauraceae. To protect host trees from beetle attack and laurel wilt infection, we tested the efficacy of host- and non-host-derived and commercial compounds as X. glabratus repellents in field experiments. In our first trial, the major constituents of the non-host tree, longleaf pine, Pinus palustris, and SPLAT Verb (verbenone 10%) were paired with manuka oil attractants and beetle captures were counted. Verbenone and a 1 : 1 blend of myrcene and camphene were intermediate to both the manuka positive and blank negative controls. Subsequently, we tested different blends of methyl salicylate (MeSA), a host defence and signalling compound, and verbenone in SPLAT dispensers using freshly cut redbay bolts as an attractant. All treatments reduced X. glabratus captures and boring holes as compared to the redbay (-) repellent positive control; however, SPLAT Verb and SPLAT MeSA-Verb (5% each) achieved the highest repellency, with results comparable to that of the non-host (laurel oak). These trials establish that host-derived and commercially available repellent compounds can reduce X. glabratus attacks and therefore have potential as part of an integrated management strategy against laurel wilt and its vector.

Verbenone and trans-conophthorin were tested against the aggregation pheromone of the six-toothed bark beetle (Ips sexdentatus Boern.) on two trapping bioassays. Two different release rates of verbenone (2 mg/24 h and 40 mg/24 h) gave similar significant catch reductions (by 73% and 82%, respectively), whereas trans-conophthorin lowered the catch by 45%. Joint release of both compounds reduced trap catches by 90%. Furthermore, the effect of these semiochemicals on Thanasimus formicarius L. and Temnoscheila coerulea Olivier, two important natural enemies of I. sexdentatus, as well as Hylurgus ligniperda Fabricius, a native associated scolytid, was evaluated. Both predators were significantly affected by verbenone, whereas the effect on H. ligniperda could not be concluded. Based on these results, verbenone was used in a third experiment to protect standing healthy Pinus nigra salzmannii J. F. Arnold trees from induced I. sexdentatus attack. The experiment consisted of two treatments and 20 paired-tree replicates. Treatments were pheromone-baited control trees and baited trees treated with verbenone (60 mg/24 h). These trees served as centres of 10 m radius plots from where a number of plot variables was recorded for local stand description. After the experimental period, all control trees had suffered attacks by I. sexdentatus, whereas trees treated with verbenone were significantly less attacked. Among other stand variables considered in the study, the following characterized the variation among plots most efficiently: (i) plot density, (ii) dominant height and (iii) the proportion of suppressed or (iv) intermediate dominance level trees in the plot. However, these variables did not significantly affect the repellent effect by verbenone. Further research should evaluate the use of verbenone on management strategies of ongoing attacks of I. sexdentatus.

A blend of eight nonhost angiosperm volatiles (benzyl alcohol, benzaldehyde, guaiacol, nonanal, salicylaldehyde, (E)-2-hexenal, (E)-2-hexen-1-ol and (Z)-2-hexen-1-ol) without [NAV] and with [NAVV] (-)-verbenone (4,6,6-trimethylbicyclo[3.1.1]hept-3-en-2-one) were tested at low (L), medium (M) and high (H) release rates for their ability to reduce attraction of western pine beetle, Dendroctonus brevicomis LeConte, to attractant-baited (exo-brevicomin [racemic, 3 mg/d], frontalin [racemic, 3 mg/d] and myrcene [18 mg/d]) multiple funnel traps. NAV-L (40 mg/d) had no significant effect. Verbenone alone (50 mg/d) and NAV-M (240 mg/d) both significantly reduced attraction, but no significant difference was observed between the two treatment means. NAV-H (430 mg/d) significantly reduced catches by ∼60% and 78% compared to verbenone alone and the baited control, respectively. In a second experiment, combining (-)-verbenone with NAV (NAVV) increased the effects observed in Experiment 1. NAVV-M (240 mg/d) resulted in an ∼69% and 83% reduction in trap catch compared to verbenone alone and the baited control, respectively. Significantly fewer D. brevicomis were captured in NAVV-H (430 mg/d) than any other treatment resulting in an ∼93% reduction in trap catch compared to the baited control. In a third experiment, NAVV was tested at three release rates for its ability to protect individual ponderosa pines, Pinus ponderosa Dougl. ex Laws., from attack by D. brevicomis. Cumulative release rates varied in direct proportion to tree diameter, but represented quarter, half and full NAVV rates. NAVV significantly reduced the density of D. brevicomis attacks, D. brevicomis successful attacks, and levels of tree mortality on attractant-baited trees. Only three of 15 NAVV-treated trees died from D. brevicomis attack while ∼93% mortality (14/15) was observed in the untreated, baited control. Quarter and half rates were ineffective for reducing tree mortality.

Monochamus galloprovincialis Olivier (Col., Cerambycidae) is a vector of the pine wood nematode, Bursaphelenchus xylophilus, causing the destructive pine wilt disease. An effective lure for monitoring and/or mass- trapping would be of great interest in the management of this pine sawyer. Males and females of this species show an attractive kairomonal response to blends composed of four pheromone compounds used by Ips spp. bark beetles and two host volatiles from pines. This six-component lure is highly attractive but may to be too complex and costly for practical use as each component is released from a separate lure. The role of each component, ipsdienol, ipsenol, cis- verbenol, methyl butenol, a-pinene and ethanol as attractants for M. galloprovincialis was field tested in Spain to obtain a simpler but equally effective bait. Ipsenol was confirmed as the strongest kairomonal signal to M. galloprovincialis synergizing response to a-pinene by 95 times. The addition of methyl butenol to this blend doubled the number of males and females trapped. On the other hand, neither ipsdienol, cis-verbenol nor ethanol improved the results when incorporated into the above three-component blend. A lure consisting of ipsenol, methyl butenol and a-pinene may be very cost-efficient in operational monitoring or mass trapping of M. galloprovincialis. Three potentially repellent candidates, ())verbenone, methyl cyclohexenone and trans-conophthorin, were also tested against the attractive three- component bait. trans-Conophthorin significantly reduced male catches of M. galloprovincialis; methyl cyclohexenone had no effect. Verbenone significantly enhanced the response of females to the attractive combination of a-pinene, ipsenol and methyl butenol.

Head-space samples of Ips typographus dead beetles taken from pheromone traps were tested by combined gas chromatography and electroantennographic detection (GC-EAD) on the antennae of the same species, and identified by GC-mass spectroscopy (MS). The GC-EAD analysis showed that antennae of both sexes responded to 1-hexanol and verbenone from the aeration samples, while the typical and strong carrion odours from the dead beetles such as dimethyl disulphide, 3-methyl-1-butenol (isoamyl alcohol), 2,5-dimethyl pyrazine and isovaleric acid elicited no antennal responses. The EAD active compounds, 1-hexanol and verbenone, have been shown in earlier studies to be inhibitory on attraction of I. typographus to pheromone traps. Thus, the decreased catching efficacy of pheromone traps with many dead beetles might be the result of the release of 1-hexanol and verbenone from the dead beetles, but not to the typical carrion smells which are strongly detected by the human nose.

Exposure to verbenone vapours did not cause any acute toxicity symptoms in the pine weevil, Hylobius abietis, whereas weevils exposed to higher doses of both limonene and α-pinene exhibited signs of poisoning within a few h. Verbenone consistently suppressed feeding, while symptom-free weevils exposed to limonene or α-pinene fed as much as controls. Feeding in verbenone-exposed weevils remained suppressed 20 h after the insects had been transferred from the exposure vials, whereas weevils exposed to limonene and α-pinene resumed normal feeding soon after transfer. Feeding deterrence by verbenone was lost after 48 h, and starved weevils were less deterred than fed weevils. Feeding was also reduced by weevils offered food contaminated by verbenone, indicating that acute toxicity effects were not responsible for the reduced feeding observed in weevils exposed to verbenone vapors. Feeding deterrence by verbenone is hypothesized to be due to its association with microbial breakdown of host tissues, indicating sub-optimal food quality.

The antiaggregation pheromone verbenone was tested at two release rates against unbaited controls for effects on mountain pine beetle, Dendroctonus ponderosae Hopk., dispersal and attack in a lodgepole pine Pinus contorta var. latifolia Dougl. stand. Number of beetles trapped, number of attacked trees and number of attacks were measured. There were no significant differences between the two verbenone treatments in any of these variables. Means of all experimental variables were lower in the verbenone-treated plots than in the control plots but only the difference in the number of beetles trapped was statistically significant. Numbers of clerid beetles trapped appeared to be unaffected by the treatments. Zusammenfassung Zur Wirkung von Verbenon auf Dispersion und Befall von Dendroctonus ponderosae Hopk. (Col., Scolytidae) in einem Pinus contorta-Bestand Das Antiaggregationspheromon Verbenon wurde in zwei verschiedenen Dosierungen in einem Pinus contorta var. latifolia Douglas-Bestand ausgebracht und hinsichtlich seiner Wirkung auf Dispersion und Befall von Dendroctonus ponderosae im Vergleich zu einer unbehandelten Flache untersucht. Folgende Parameter wurden bei der Untersuchung erfast: Zahl der gefangenen Kafer, Zahl der befallenen Baume und Anzahl der Einbohrungen. Bei keinem dieser Faktoren ergab sich zwischen den zwei mit Verbenon behandelten Flachen ein Unterschied. Zwar waren alle Mittelwerte der Unter-suchungsparameter auf den behandelten Flachen niedriger als auf den Kontrollflachen, aber ein statistisch gesicherter Unterschied bestand nur hinsichtlich der Zahl gefangener Kafer. Die Anzahl mitgefangener Cleridae wurde offensichtlich durch die Behandlung nicht beeinflust.

Colonization densities of the pine shoot beetle, Tomicus piniperda, and the ash bark beetle, Leperisinus varius, respectively, on bolts cut from Scots pine (Pinus sylvestris), and ash (Fraxinus excelsior) were significantly reduced after spraying the bolts with emulsion of synthetic verbenone or a plant oil containing predominately ipsdienone. In both bark beetle species, host odours play an important role in triggering aggregation behaviour while pheromones are of minor importance, if at all (.)

Use of the Dendroctonus frontalis inhibitor pheromone verbenone, as a treatment on trees within infestations, is effective in suppressing or halting infestation growth. It is hypothesized that the inhibitor disrupts the orientation of flying adult D. frontalis to host trees and, as a result, sufficient attacking adults are not available at any given time on a tree to successfully over take it. Seasonal changes in abundance, longevity, and dispersal of beetle populations may impact the effectiveness of the inhibitor-based treatment. Zusammenfassung Die Verhinderung der Ausdehnung von Dendroctonus frontalis-(Col., Scolytidae-)Befall mit einem Ablenkstoff Die Anwendung des Ablenkstoffes Verbenon in Borkenkaferherden von Dendroctonus frontalis ist ein wirksames Mittel zur Verhinderung der Ausbreitung weiteren Befalls. Es wird angenommen, das der Ablenkstoff die Orientierung der fliegenden Kafer auf der Suche nach Wirtsbaumen unterbindet und, als Folge, zu keiner Zeit genugend Kafer vorhanden sind, um einen Baum erfolgreich anzugreifen. Jahreszeitlicher Wechsel in der Abundanz, Lebenszeit und Dispersion mogen Einflus auf die Wirksamkeit des Ablenkstoff-Verfahrens haben.

Under field conditions, the pheromone attractant responses of the scolytids Orthotomicus erosus and Ips sexdentatus were significantly reduced by the addition of one of the oxidation products of α-pinene, verbenone, to the attractive volatiles 2-methyl-3-butene-2-ol plus ipsdienol. Catches in flight barrier traps also decreased when (S)-cis-verbenol was added to the dual bait mixture; the inhibitory action of the terpene alcohol was more noticeable upon the female populations of both species. The observed patterns of behavior might reflect the outcome of a long process of competition among Ips species. Zusammenfassung Hemmende Wirkung von (S)-cis-Verbenol und Verbenon auf die Anlockung von Orthotomicus erosus (Woll.) und Ips sexdentatus Boern. (Col., Scolyudae) an Pheromonfalien Die Lockwirkung der Pheromonkombination 2-Methyl-3-Buten-2-ol plus rac. Ipsdienol auf Orthotomicus erosus und Ips sexdentatus wurde durch den Zusatz von Verbenon stark reduziert. Wenn die Lockstoffkombination zusammen mit (S)-cis-Verbenol ausgebracht wurde, war die Zahl der in Flugbarrierefallen gefangenen Kafer ebenfalls wesentlich geringer. Dabei hemmte der Terpenalkohol den Anflug der Weibchen starker als den der Mannchen. Das beobachtete Verhaltensmuster wird als Ergebnis einer interspezifischen Konkurrenz zwischen den sympatrischen Ips-Arten gedeutet.