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Individuals across various animal species communicate their presence to conspecifics. Especially phytophagous and parasitoid insects with their brood developing on limited resources rely on chemical cues, such as host-marking pheromones, to reduce intraspecific competition. Bark beetles are phytophagous insects with some species being economically and ecologically relevant forest pests. Several of them use the volatile compound verbenone to inhibit attraction and reduce intraspecific competition. However, in the Eurasian spruce bark beetle, Ips typographus (L.), temporal emission patterns did so far not quite support the putative function of verbenone as an indicator of densely colonised host trees. More importantly, it is currently unclear how well verbenone emission is actually related to colonisation density and thus intraspecific competition. Here, we inoculated Norway spruce logs with I. typographus at two defined colonisation densities in the greenhouse and measured the emission of verbenone and its precursors α-pinene and verbenol over time. Verbenone emission was 3–7 times greater from colonised logs compared to decaying logs without beetles during the major part of larval development. Furthermore, our data supports the quantitative hypothesis, that the termination of attack on a tree is mediated by a cessation of the release of verbenol and continuous emission of verbenone. The latter is most likely a passively produced host-marking cue reflecting the actual density of conspecifics since per-beetle emission was unaffected by colonisation density. These findings shed new light on the regulation of bark beetle mass aggregations, which are currently causing previously unseen economic damages in temperate forests. [ABSTRACT FROM AUTHOR]

The polyphagous shot hole borer (PSHB), Euwallacea fornicatus (Eichhoff), is an ambrosia beetle (Coleoptera: Curculionidae) infesting avocado branches Persea americana Mill. in North America, South Africa and Israel. Field experiments were conducted with attractive quercivorol traps and repellents on trees to develop push–pull control methods. PSHBs were collected over the summer from multiple-funnel traps baited with quercivorol in grids of low-, medium- and high-density traps to assess mass trapping interactions and capture trends. Mean catch/trap-week was higher on peripheral outer traps compared to the next inner ring of traps in grids. These ratios and grids were simulated to estimate the circular effective attraction radius (EARc) of multiple-funnel traps and compared to a previous relationship for sticky traps yielding EARc from release rate of quercivorol. The results indicate that multiple-funnel traps have smaller EARc in higher-density grids, likely due to interactions between traps. Tests with verbenone compared to methyl salicylate (MeSA) indicate both are repellents and no evidence for synergism. Dollops of verbenone–MeSA–SPLAT (5% each volatile) were applied monthly at 10- and 40-cm spacings along branched trunks of avocado trees, with release of volatiles declining exponentially over a month. These treatments caused a reduction in both numbers of aggregations/tree and attacks/aggregation to about half that of untreated control trees. Verbenone–MeSA–SPLAT dollops caused localized phytotoxicity on avocado bark, suggesting 8 cm2 plastic bag dispensers containing 0.25 g verbenone are preferred at 40-cm spacing. Push–pull should be done just before flight season to overwhelm natural attraction of single females initiating aggregations. [ABSTRACT FROM AUTHOR]

Two pine shoot beetles, Tomicus yunnanensis and Tomicus minor, are the most destructive pests of Pinus yunnanensis in southwestern China. We investigated behavioral responses within and between these two species during the shoot-feeding phase using walking bioassays. We also identified the pheromonal aspects of beetles by static solid phase microextraction (SPME) and hindgut extraction following interactive communication by gas chromatography-mass spectroscopy (GC-MS). Both species were significantly attracted by their own species and the same sex, and attraction was inhibited by exposure to additional beetles or to the hindgut extracts of beetles which had shown interaction. Female and male T. minor and T. yunnanensis hindguts contained 0.19, 0.09, 0.22, and 0.05 ng/individual of (−)-trans-verbenol, respectively; following interaction with additional beetles, this increased to 16.74–292.71 ng/individual in T. minor females. Mean concentration of verbenone detected in the hindguts of female/male individuals of T. minor and T. yunnanensis under natural conditions were 0.16, 0.06, 0.03, and 0.05 ng/individual, respectively, but these correspondingly increased to 5.90, 2.43, 0.06, and 0.19 ng/individual after exposure to additional insects. In T. yunnanensis, the amounts of detectable (−)-trans-verbenol and verbenone extracted from hindguts were lower than those from T. minor. The levels of cis-verbenol and (−)-trans-verbenol most attractive to walking T. yunnanensis and T. minor were 0.1 and 1.0 ng/μl, respectively. Verbenone was not attractive at any of the concentrations tested. The addition of verbenone to cis-verbenol or (−)-trans-verbenol reduced the attraction responses. We conclude that the (−)-trans-verbenol produced by these two pine shoot beetles is attractive at low concentrations and repellant at high concentrations, thereby fostering intraspecific competition. Verbenone is produced to prevent overcrowding via interspecific inhibition, and to expel beetles during shoot-feeding. [ABSTRACT FROM AUTHOR]

The Euwallacea fornicatus (Eichhoff) species complex includes the polyphagous shot hole borer (PSHB), an ambrosia beetle infesting avocado limbs, Persea americana Mill. Synthetic quercivorol, a monoterpene alcohol, is known to attract females (males are flightless) over a range of release rates spanning three orders of magnitude. The upper release dose was extended 10-fold using sticky traps baited with quercivorol released at 1× (0.126 mg/day), 10×, and 108× relative rates to obtain a dose−response curve fitting a kinetic formation function. Naturally infested limbs of living avocado trees were wrapped with netting to exclude the possibility of catching emerging beetles on the encircling sticky traps. The results indicate PSHB are significantly attracted to infested limbs. Ethanol released over a 64-fold range (lowest rate of 7.5 mg/day) was moderately inhibitory of PSHB attraction to 1× quercivorol. β-caryophyllene and eucalyptol did not appear to affect attraction at the rates tested. A field test of potential inhibitors of 1× quercivorol was done using ~1 mg/day releases of monoterpene ketones: (−)-(S)-verbenone, (+)-(R)-verbenone, 3-methyl-2-cyclo-hexen-1-one (MCH or seudenone), piperitone, (+)-(S)-carvone, and racemic cryptone. Only piperitone and the two enantiomers of verbenone were strongly inhibitory. A blend of piperitone and verbenone tested together at different distances (0, 0.5, 1, 2, and 4 m) from a 1× quercivorol baited sticky trap became increasingly ineffective in inhibiting the attractant as separation distance increased. Due to the relatively short-range repellency (<1 m), the inhibitors would need to be released from several places on each tree to effectively repel PSHB from avocado trees. Effective attraction radii, EAR, and circular EARc are estimated for the quercivorol baits released at 1×, 10× and 108× rates. Push-pull simulations of moving beetles were performed in 1 ha plots with 2, 4, or 16 traps of 10× EARc and 400 trees (0, 1, or 3 inhibitors per tree) of which ten had an infested limb (EARc = 0.5 m). The simulations indicate that push-pull methods would be more effective in reducing PSHB mating than simply using mass-trapping alone. [ABSTRACT FROM AUTHOR]

Bark beetles are the most important mortality agent in coniferous forests, and pheromones play important roles in their management. Dendroctonus valens LeConte was introduced from North America to China and has killed millions of healthy pines there. Trapping with semiochemicals and pheromones was deployed in D. valens management in the last decade, but little is known about the ability of gut bacteria to produce the pheromone. In this study, we analyzed the volatiles in D. valens guts and frass after antibiotic treatment versus control. Then, we isolated and identified the bacteria in D. valens guts and frass, examined verbenone (a multifunctional pheromone of D. valens) production by 16 gut bacterial isolates from the precursor cis-verbenol at three concentrations, and further compared the cytotoxicities between the cis-verbenol and verbenone to the bacterial isolates. cis-Verbenol was not detected in the frass in the control group, but it was in the antibiotic treatment. The amount of verbenone was significantly suppressed in D. valens guts after antibiotic treatment versus control. Thirteen out of 16 gut bacterial isolates were capable of cis-verbenol to verbenone conversion, and cis-verbenol had stronger cytotoxicities than verbenone to all tested gut bacterial isolates. The bacterial species capable of verbenone production largely exists in D. valens guts and frass, suggesting that gut-associated bacteria may help the bark beetle produce the pheromone verbenone in guts and frass. The bacteria may benefit from the conversion due to the reduced cytotoxicity from the precursor to the beetle pheromone. [ABSTRACT FROM AUTHOR]

A number of compounds with a substituted hexahydro-2 H-4,6-(epoxymethano)chromen8(5 H)-one framework was synthesized starting from monoterpenoid (-)-verbenone and aromatic aldehydes containing methoxy and hydroxy groups. Cytotoxic activity of these compounds on human tumor cell lines was studied for the first time. Compounds containing three methoxy groups in each aromatic ring were found to be the most promising for further studies. [ABSTRACT FROM AUTHOR]

After separation of crystalline bisulfite derivatives of enantiomerically enriched (1 S)- and (1 R)-verbenones, steam distillation of the filtrates afforded (1 S)- and (1 R)-verbenones whose optical purity was higher by 30 and 20%, respectively, than that of the initial enantiomers. [ABSTRACT FROM AUTHOR]

The article provides information regarding herbaceous perennial Chloranthus serratus and the use of its root to make essential oils. The article also discusses the chemical composition of the oil including Verbenone, Santalen, and Nerolidol. The article also reports that the oil could be used to treat various problems including traumatic injury, rheumatism, and snake bite.

The first synthesis of p-mentha-1,8-diene triol from (−)-verbenone included obtaining pinane epoxy diol and its subsequent acid-catalyzed rearrangement on montmorillonite clay as the key steps. [ABSTRACT FROM AUTHOR]

This review considers the synthetic possibilities of monoterpene ketones, such as (R)-(+)- and (S)-(-)-pulegones, (-)-menthone, (R)-(-)- and (S)-(+)-carvones, (2R,5S)-dihydrocarvone, (S)-(+)- and (R)-(-)-camphors, (R)-(-)-nopinone, (R)-(+)- and (S)-(-)-verbenones by the examples of synthesis of optically pure and enantiomerically enriched insect pheromones. [ABSTRACT FROM AUTHOR]

The conditions of ozonolysis of verbenone in methanol strongly affect the mechanism of formation of the major product, (1 R,3 S)-3-acetyl-2,2-dimethylcyclobutane-1-carboxylic acid. [ABSTRACT FROM AUTHOR]

Results from a systematic study of the factors affecting extraction of cis-verbenol and verbenone from pine seeds are presented. Five extraction conditions were investigated: extraction solvent, method of extraction, extraction temperature, volume of solvent, and the ratio of the mass of sample to the amount of extraction solvent. The resulting optimized method uses magnetic-stirring-assisted extraction of pine seeds (5 g) with ethyl acetate (75 mL) for 20 min, at room temperature. RSDs were less than 5% for both compounds. GC–FID was used for quantification of cis-verbenol and verbenone in the extracts. [ABSTRACT FROM AUTHOR]

Reduction of verbenone with NaBH4 in the presence of Ce(NO3)3·6H2O (10—20 mol %) proceeds stereoselectively to give cis-verbenol in 89—94% yield. [ABSTRACT FROM AUTHOR]

Leaf and bark volatiles from nonhost angiosperm trees were tested on Ips duplicatus by gas chromatographic–electroantennographic detection (GC-EAD) and by pheromone-baited traps in Sweden and Inner Mongolia, China, respectively. GC-EAD analysis of the headspace volatiles from fresh bark chips of Betula pubescens revealed trans-conophthorin, two green leaf volatiles (GLVs): 1-hexanol and (Z)-3-hexen-1-ol, and two C8 alcohols: 3-octanol and 1-octen-3-ol, that consistently elicited antennal responses by I. duplicatus. The identification of these EAD-active compounds was confirmed in further GC-EAD recordings with synthetic mixtures. Antennal responses were also found to synthetic (E)-2-hexen-1-ol and linalool, which have been identifed from the leaves of nonhost birch and aspen species. No antennal responses of I. duplicatus were found to hexanal, (E)-2-hexenal, and (Z)-3-hexyl acetates. In field trapping experiments, blends of EAD-active green leaf alcohols or C8 alcohols, or trans-conophthorin alone resulted in significant reductions (27–60%) in the number of I. duplicatus captured compared with pheromone-baited traps. The unsuitable host compound, verbenone (Vn), also significantly reduced trap catches by up to 60% in both experiments. The strongest disruptive effect resulted from the addition of the combination of green leaf alcohols, C8 alcohols, and verbenone to the pheromone trap, which caused an 84% reduction in trap catch. The blend of two green leaf aldehydes plus the acetate increased the trap catches in 1998 and had no negative or positive effects in 1999. Our results suggest that these nonhost volatiles (NHVs) are important olfactory signals used by I. duplicatus in host selection. They may have great significance in developing semiochemical-based management programs for I. duplicatus by reducing or stopping attacks on suitable hosts. [ABSTRACT FROM AUTHOR]

Cellulose triacetate was investigated as a chiral stationary phase for preparatively separating the enantiomers of lineatin, frontalin, exo-brevicomin, endo-brevicomin, verbenone, (E)-conophthorin, and grandisol. Tens of milligrams of both enantiomers were efficiently prepared in high percentage enantiomeric excess from one injection of each compound except grandisol. We prepared grandisyl acetate, benzoate, and 4-bromobenzoate to determine if derivatization of the free alcohol might improve separation. Of these, grandisyl 4-bromobenzoate provided the best separation but was still not very well resolved. Preparative separation of enantiomers on cellulose triacetate is a viable alternative to stereoselective synthesis when semiochemicals of very high enantiomeric purity are required for biological testing. [ABSTRACT FROM AUTHOR]

α pinene can be oxidised to verbenone with ca. 60% selectivity using a commercial silica–titania co gel catalyst with tert butyl hydroperoxide as oxidant. Using cyclohexene as a model reagent, it is suggested that the formation of verbenone is probably via the formation of a hydroperoxy intermediate. [ABSTRACT FROM AUTHOR]

Ips cembrae adults were collected from larch log piles in northeast China, separated into six attack phases, and immediately frozen in liquid nitrogen. Three previously described aggregation pheromone components [ipsenol, ipsdienol, and 3-methyl-3-buten-1-ol (331-MB)] and six other volatiles of beetle origin (2-phenylethanol, geraniol, ipsenone, ipsdienone, myrtenol and verbenone) were identified and quantified by GC-MS from excised male hindguts. No amitinol, a recently reported aggregation pheromone component, was detected in our samples. The amounts of these volatiles (except the last two) showed a similar pattern of variation between attack phases in males. The largest amounts of most male volatiles were present in phases 1–2, when the nuptial chamber was being constructed or only one female was accepted. The amounts of the volatiles declined sharply in the following phases. The hindgut volatiles, mainly the pheromone components, from 46 individual males in phase 1 were also quantified. Ipsenol, ipsdienol, and 331-MB showed a large variation in both amounts and proportions. The chirality of these two dominant aggregation pheromone components was determined as 100% (−)-enantiomer of ipsenol and 96% (+) enantiomer of ipsdienol. No male aggregation pheromone components were detected from mated females, except three extracts that were probably contaminated by male tissues. [ABSTRACT FROM AUTHOR]

A synthetic mixture of nine green leaf volatiles (GLVs) including linalool was tested on antennae of Ips typographus (L.) with coupled gas chromatographic–electroantennographic detection (GC-EAD). Strong responses were found to 1-hexanol, ( Z)-3-hexen-1-ol, and ( E)-2-hexen-1-ol. Weak responses were recorded to ( E)-3-hexen-1-ol, ( Z)-2-hexen-1-ol and linalool, while hexanal, ( E)-2-hexenal and ( E)-3-hexenyl acetate elicited no EAD responses. In a laboratory walking bioassay, the attraction of I. typographus females to a synthetic pheromone source was significantly reduced when a mixture of the three most EAD-active GLV alcohols was added to the source. Further reduction in response was obtained when these three alcohols were combined with verbenone (Vn). In field trapping experiments, a blend of 1-hexanol, ( Z)-3-hexen-1-ol, and ( E)-2-hexen-1-ol reduced I. typographus trap catches by 85%, while ca. 70% reduction of trap catch was achieved by Vn or a blend of ( E)-3-hexen-1-ol, ( Z)-2-hexen-1-ol, and linalool. The strongest disruptive effect was found when Vn plus a blend of the three most EAD active GLV alcohols was added to the pheromone trap (95% catch reduction). Adding the blend of the three most EAD active alcohols to pheromone-baited traps significantly reduced the proportion of males captured. These three GLV alcohols were also disruptive in the laboratory and in the field when tested individually. Hexanal, ( E)-2-hexenal, and ( Z)-3-hexenyl acetate were inactive both in the lab and in the field. Our results suggest that these nonhost green leaf alcohols may explain part of the host selection behavior of conifer-attacking bark beetles and may offer a source of inhibitory signals for alternative management strategy for forest protection. [ABSTRACT FROM AUTHOR]

In spring, the landing rate of flying European pine shoot beetles, Tomicus piniperda L., on injured Scots pine diminishes as colonization continues. This is due to olfactory cues that indicate progressive host degradation. Verbenone was shown to play a role in the beetle's recognition of this unsuitability of a formerly suitable host, since the compound was increasingly released from colonized tree sections as they aged, but not from uninfested sections. Also, the release of verbenone at natural rates in the forest inhibited the attraction of beetles to host monoterpenes. [ABSTRACT FROM AUTHOR]

The aggregation pheromone produced by male Ips paraconfusus (Coleoptera: Scolytidae) tunneling in Monterey pine, Pinus radiata, logs was trapped on Porapak Q. A concentration of an extract of trapped volatiles that attracted beetles was determined in the laboratory through a concentration–response analysis of walking behavior of males and females. The interruptant effects of four concentrations of verbenone on response to a constant concentration of this naturally produced aggregation pheromone were tested with males and females. Independent of its enantiomeric composition [99.5% ( S)-(−), 93.1 % ( S)-(−), and 98.3% ( R)-(+)], verbenone significantly reduced the percentage of females (but not males) reaching the attractant source. However, when the time required for beetles of both sexes taken together to reach the attractant source was considered, verbenone of higher enantiomeric purity had a greater effect on beetle behavior. Solutions of 99.5% ( S)-(−)- and 98.3% ( R)-(+)-verbenone increased the time required for beetles to reach the attractive source when compared to 93.1% ( S)-(−)-verbenone. When pooled across enantiomeric blends, increasing concentrations of verbenone resulted in slower responses in beetles that reached the attractant source within 2 min. Males and females did not respond to verbenone alone. [ABSTRACT FROM AUTHOR]

The article discusses the stereospecific synthesis of the organic compound cis-Verbenol. Topics discussed include the reduction of the terpene 1S,5S-verbenone with the organoaluminum compound (i-Bu)2AlH, the physicochemical analysis of the compound, and the stereospecificity of formation of cis-Verbenol.