Pine shoot beetle, Tomicus piniperda (Col., Scolytidae), responses to common green leaf volatiles

We tested the hypothesis that green leaf volatiles (GLVs) disrupt the response of overwintered pine shoot beetles, Tomicus piniperda (L.) to multiple-funnel traps baited with the attractive host volatile α-pinene. A combination of four GLV alcohols, 1-hexanol ( E )-2-hexen-1-ol ( Z )-2-hexen-1-ol, and ( Z )-3-hexen-1-ol, caused 54 and 36% reduction in the number of pine shoot beetles captured in two separate trapping experiments. Similarly, a combination of the four alcohols plus two GLV aldehydes, hexanal and ( E )-2-hexenal, caused 38% reduction in the number of pine shoot beetles captured compared with α-pinene alone. A blend of the two GLV aldehydes was not disruptive. None of the four GLV alcohols nor the two GLV aldehydes were disruptive when tested individually. The finding that the blend of four GLV alcohols reduced attraction of T. piniperda supports the general hypothesis that GLVs common to nonhost angiosperms are disruptive to conifer-attacking bark beetles (Scolytidae).     

New metabolites of α-pinene produced by the mountain pine beetle,Dendroctonus ponderosae (Coleoptera: Scolytidae)

Emergent females of the mountain pine beetle, Dendroctonus ponderosae, contained five previously undetected volatiles: toluene, 4-methylene-6,6-dimethylbicyclohept-2-ene (verbenene), p-mentha-1,5,8-triene, o- and p-cymene. Exposure of wild or axenically reared beetles to protio- and deuterio-α-pinene or protio- and deuterio-trans-verbenol indicated that all compounds except toluene were produced from α-pinene, with trans-verbenol as a probable intermediate. The ratio between these α-pinene metabolites was insensitive to the level of α-pinene to which the beetles were exposed, suggesting a tightly regulated enzymatic and/or acid-catalyzed conversion of α-pinene. Exposure of females to either enantiomer of α-pinene or to the same amount of (±)-α-pinene indicated that female mountain pine beetles possess two enantiospecific enzyme systems for processing α-pinene. Production of p-cymene constitutes the first record in an insect of an aromatic volatile produced from a monoterpene hydrocarbon.     

Feeding of large pine weevil on Scots pine stem triggers localised bark and systemic shoot emission of volatile organic compounds

Feeding by the large pine weevil (Hylobius abietis L.) causes severe damage to the bark of Scots pine (Pinus sylvestris L.) seedlings. We measured photosynthesis, the emission of volatile organic compounds from intact and weevil-damaged bark and systemic emissions from undamaged foliage. Feeding damage did not affect photosynthesis. Monoterpenes dominated the emissions from the feeding site, although some sesquiterpenes were also emitted. Weevil feeding increased bark emission of monoterpenes by nearly 4-fold and sesquiterpenes by 7-fold. The influence of weevil damage on systemic monoterpene emissions from shoots was more profound. Several compounds were substantially induced, including linalool, β-phellandrene, limonene and 1,8-cineole. Sesquiterpenes contributed only 1.2% of the total foliage emission, but comprised eight different compounds including (E,E)-α-farnesene, β-bourbonene and (E)-β-farnesene. The total emission of monoterpenes and sesquiterpenes from shoots was respectively 2.8-fold and 2.9-fold higher in the pine weevil damaged plants than the undamaged plants. As many of the induced compounds are highly reactive in the atmosphere and form organic aerosol particles, our results suggest that conifers damaged by insects could become a more important source of secondary organic aerosols than healthy trees.     

Investigations on the spontaneous emitted and hydrodistilled volatiles of Platycladus orientalis (L.) Franco grown in four different biogeographic zones of Jordan

The essential oil of the fresh leaves of Platycladus orientalis (L.), grown in four different biogeographic zones of Jordan,- (the Mediterranean, Irano-Turanian, Saharo-Arabian, and Sudanian penetration) -, were obtained by hydrodistillation and analysed by gas chromatography (GC) and gas chromatography-mass-spectrometry (GC/MS). The actual composition of the spontaneous emitted volatiles was obtained using the solid-phase-micro-extraction (SPME) method and investigated using the same chromatographic and spectroscopic methods. Hydrocarbon monoterpenes dominated the hydrodistilled oils and emissions of all regions. Bicyclic monoterpenes (sabinene, α-pinene, and α-thujene) and monocyclic α-terpinene were detected as the major constituents of the oils and emissions. Additionally, hierarchical cluster analysis (HCA) revealed that the clustering is based on the region of collection rather than the applied methodology. Differences were observed in the quantity of the obtained oils (P-values <0.01); the highest amount of volatile oil was obtained from samples grown in the Irano-Turanian biogeographic zone.     

A fungal metabolite masks the host plant odor for the pine weevil (Hylobius abietis)

The pine weevil is one of the most important pest insects of conifer reforestation areas in Europe. Female pine weevils cover their eggs with chewed bark and feces (frass) resulting in avoidance behavior of feeding conspecifics towards egg laying sites. It has been suggested that microorganisms present in the frass may be responsible for producing deterrent compounds for the pine weevil. The fungi Ophiostoma canum, O. pluriannulatum, and yeast Debaryomyces hansenii were isolated from aseptically collected pine-weevil frass. The isolated fungi were cultured on weevil frass broth and their volatiles were collected by SPME and identified by GC–MS. D. hansenii produced methyl salicylate (MeS) as a major compound, whereas, in addition, O. canum and O. pluriannulatum produced 6-protoilludene. In a multi-choice lab bioassay, MeS strongly reduced pine weevil's attraction to the Pinus sylvestris volatiles. Thus, a fungal metabolite was found that strongly affects the pine weevil host-odor search.     

Monoterpenes emitted by the large pine weevil, Hylobius abietis (L.) feeding on Scots pine, Pinus sylvestris L.

Abstract. Attraction of the large pine weevil, Hylobius abietis (L.) (Coleoptera: Curculionidae) to pine logs was enhanced by the presence of weevils already on the logs. We investigated the volatiles emitted by insects feeding on host trees to determine the mechanism of the attraction. Chemical analyses of the collected volatiles showed large amounts of monoterpenes. There were no qualitative differences in the collections, between Scots pine alone and pine plus feeding weevils, nor between males and females, mated or virgin. Strong quantitative differences in monoterpenes existed that were correlated to the surface of cut bark. Electroantennograms (EAGs) were recorded on male and female antennae stimulated by increasing doses of collected volatiles. EAGs for pine alone and pine plus weevils at the same stimulus loading in (a + P)-pinene gave superimposable curves. EAGs of male and female volatiles were also identical. These results suggest an attraction mediated by host plant allelochemicals rather than by an aggregation pheromone.     

Impact of flooding and drought conditions on the emission of volatile organic compounds of Quercus robur and Prunus serotina

We conducted measurements with oak (Quercus robur L.) and black cherry (Prunus serotina Ehrh.) seedlings to investigate their volatile organic compound (VOC) emission behavior to flooding and drought conditions. A novel cuvette enclosure approach was applied on 18 individuals and emission rates were derived using proton transfer reaction-mass spectrometry (PTR-MS) and gas chromatography–mass spectrometry (GC–MS) techniques. Complementary chlorophyll fluorescence and CO₂ uptake measurements were performed for all of the samples. Q. robur seedlings remained unaffected by flood. On the contrary, P. serotina seedlings reduced their chlorophyll fluorescence yield by 34.5 ± 4.1 % and their CO₂ uptake by 67.5 ± 10.5 %. These observations along with the highest acetaldehyde emissions recorded indicate strong susceptibility to water stress. Drought had a similar impact on both species that reduced chlorophyll fluorescence yield, CO₂ uptake, and the emission rates of most VOC. Nevertheless, isoprene was found to be emitted more than 20 times stronger by Q. robur seedlings under all treatments. In general, most VOC emissions increased with soil water availability displaying an exponential trend for acetaldehyde and methanol and a linear one for the sum of mono- and sesquiterpenes. Only methyl salicylate was released about two times stronger from oaks under drought conditions in comparison to wet conditions. Considering their VOC emission behavior, Q. robur seedlings appear to tolerate flood much better than P. serotina and thus it is likely to have a competing advantage under these conditions.     

Terpene composition of Pinus pinaster seedlings and plants

-The production of essential oils in Pinus pinaster increases with the age of the seedlings, being higher in plants grown under continuous illumination. In the seedlings, nearly all the terpene is α- and β-pinene, the relative proportions of which are completely reversed between the 6th and 10th days of growth, regardless of the illumination period. Another reversion takes place after 60–65 days, the proportion found in the adult pine being very constant with α-pinene as the main component. The amount of oil in seedlings from high resin yielding parent trees was 4-fold higher than that in seedlings of normal (wild type) seeds. This finding is interesting because it can be employed for the preselection at the early stage of seedling of seeds to be used in forestry to obtain plantations of a high resin yield.     

Effects of phosphorus availability and genetic variation of leaf terpene content and emission rate in Pinus pinaster seedlings susceptible and resistant to the pine weevil, Hylobius abietis

We studied the effects of phosphorus fertilisation on foliar terpene concentrations and foliar volatile terpene emission rates in six half-sib families of Pinus pinaster Ait. seedlings. Half of the seedlings were resistant to attack of the pine weevil Hylobius abietis L., a generalist phloem feeder, and the remaining seedlings were susceptible to this insect. We hypothesised that P stress could modify the terpene concentration in the needles and thus lead to altered terpene emission patterns relevant to plant-insect signalling. The total concentration and emission rate ranged between 5732 and 13,995 μg·g(-1) DW and between 2 and 22 μg·g(-1) DW·h(-1), respectively. Storage and emission were dominated by the isomers α- and β-pinene (77.2% and 84.2% of the total terpene amount amassed and released, respectively). In both resistant and susceptible families, P stress caused an increase of 31% in foliar terpene concentration with an associated 5-fold decrease in terpene emission rates. A higher terpene content in the leaves implies that the 'excess carbon', available under limiting growth conditions (P scarcity), is allocated to terpene production. Sensitive families showed a greater increase in terpene emission rates with increasing P concentrations, which could explain their susceptibility to H. abietis.     

Pine weevil damage to Norway spruce seedlings: effects of nutrient‐loading,soil inversion and physical protection during seedling establishment

• 1 The pine weevil Hylobius abietis (L.) feeds on the bark of young conifer seedlings and is one of the most economically important forest pests in Europe.
• 2 In a field experiment, we examined the combined effects of the treatments: nutrient‐loading of seedlings, planting in scarified plots and protection of seedlings against pine weevil damage for either half a season or a full season.
• 3 Nutrient loading had no significant effect on the amount of pine weevil feeding.
• 4 Seedling mortality was significantly reduced when seedlings were protected from pine weevil feeding during establishment. This occurred even though the debarked area of protected seedlings 5 weeks after the shields had been removed was similar to that of the unprotected seedlings. This indicates that initial protection rendered the seedlings more tolerant to later wounding by pine weevil.
• 5 Planting in soil inversion significantly reduced feeding compared with planting in humus.
• 6 We conclude that nutrient‐loading of seedlings in the autumn before planting would not increase pine weevil feeding after planting. Mortality could be reduced by treatments that postpone the start of pine weevil feeding on seedlings. Such treatments, combined with planting in soil inversion, would result in increased seedling growth, vitality and tolerance to pine weevil attack.

     

Influence of host log age and refuge from natural enemies on colonization and survival of Phoracantha semipunctata

The pine cone weevil, Pissodes validirostris Gyll. (Coleoptera: Curculionidae), attacks seed cones of most Eurasian pine species, except these of Swiss stone pine (Pinus cembra L.). Behavioural responses of adult weevils to cone volatile emissions of Swiss stone pine and to those of a common host, mountain pine (Pinus uncinata Ram.), were compared in an olfactometer. Weevils were significantly attracted by the volatile blend emitted by mountain pine, but Swiss stone pine volatiles elicited an inverse response, with most weevils moving in the opposite direction to the odour source. However, the majority of second instar weevil larvae that were extracted from mountain pine cones and transferred into Swiss stone pine cones were capable of developing to the adult stage. This suggests that Swiss stone pine cones do not contain strong feeding deterrents that could prevent larval development. The possible factors involved in the absence of colonization of Swiss stone pine cones by cone weevils are discussed.     

Shared signals -'alarm calls' from plants increase apparency to herbivores and their enemies in nature

The attraction of natural enemies of herbivores by volatile organic compounds as an induced indirect defence has been studied in several plant systems. The evidence for their defensive function originates mainly from laboratory studies with trained parasitoids and predators; the defensive function of these emissions for plants in natural settings has been rarely demonstrated. In native populations and laboratory Y-tube choice experiments with transgenic Nicotiana attenuata plants unable to release particular volatiles, we demonstrate that predatory bugs use terpenoids and green leaf volatiles (GLVs) to locate their prey on herbivore-attacked plants. By attracting predators with volatile signals, this native plant reduces its herbivore load – demonstrating the defensive function of herbivore-induced volatile emissions. However, plants producing GLVs are also damaged more by flea beetles. The implications of these conflicting ecological effects for the evolution of induced volatile emissions and for the development of sustainable agricultural practices are discussed.     

Induced defenses of Veronica spicata: Variability in herbivore-induced volatile organic compounds

Plants release volatile organic compounds (VOCs) that have many eco-physiological functions. Induction of plant VOCs is known to occur upon herbivory. Herbivore-induced VOCs are involved in the attraction of predators and parasitoids, a phenomenon known as an indirect defense of plants. We measured the VOC profiles of the wild species Veronica spicata with and without larval feeding and oviposition by the specialist butterfly Melitaea cinxia. V. spicata showed great plasticity when deploying indirect defences. The induction of several ubiquitous terpenoids and green leaf volatiles (GLVs) was associated with larval feeding, whereas the increase of two ketones, 6-methyl-5-hepten-2-one and t-geranylacetone and the suppression of GLVs were associated with oviposition by the butterfly.     

Host-plant acceptance on mineral soil and humus by the pine weevil Hylobius abietis (L.)

1 The pine weevil Hylobius abietis (L.) (Coleoptera, Curculionidae) is an economically important pest of conifer forest regeneration in Europe and Asia. 2 Soil scarification, which usually exposes mineral soil, is widely used to protect seedlings from weevil attack. However, the mechanism behind this protective effect is not yet fully understood. 3 Field experiments were conducted to determine the pine weevil's responses to visual and odour stimuli from seedlings when moving on mineral soil and on undisturbed humus surface. 4 One experiment measured the number of pine weevils approaching seedlings, with and without added host odour, on mineral soil and undisturbed humus. Seedlings with added host odour attracted more weevils on both soil types. Unexpectedly, somewhat more weevils approached seedlings surrounded by mineral soil. 5 In a similar experiment, feeding attacks on seedlings planted directly in the soil were recorded. Only half as many seedlings were attacked on mineral soil as on undisturbed humus. 6 In the first experiment, the weevils were trapped 2.5 cm from the bases of the seedlings' stems, whereas they could reach the seedlings in the experiment where seedlings were planted directly in the soil. We conclude that the pine weevils' decision on whether or not to feed on a seedling is strongly influenced by the surrounding soil type and that this decision is taken in the close vicinity of the seedling. The presence of pure mineral soil around the seedling strongly reduces the likelihood that an approaching pine weevil will feed on it.     

油松球果小卷蛾成虫的产卵选择

油松球果小卷蛾Gravitarmata margarotana(Heinemann)是广泛分布的一种松属球果和枝梢害虫,在我国北方油松良种基地主要危害油松球果。用油松和华山松球果做产卵选择试验,以及2树种球果浸提液对产卵影响的结果表明,油松球果对产卵雌虫具有更强的引诱作用;不同油松球果类型的着卵量结果表明,红色球果类型的着卵量显著高于绿色球果类型,并且同一颜色球果,有刺类型的着卵量多于无刺类型。球果挥发成分结果表明,油松球果挥发成分有6个组分,而华山松球果挥发成分只有5个组分,与油松球果相比,无β-非兰烯组分;油松不同株系类型球果挥发成分只表现出含量上的差异。     

Variation in needle terpenoids among Pinus sylvestris L. (Pinaceae) provenances from Turkey

Variation of terpenes and resin acids in needles of young Scots pine (Pinus sylvestris L.) seedlings from nine different provenances in Turkey was investigated. The provenances represent 1200-km West to East and 400-km South to North transects. Seven monoterpenes and two sesquiterpenes were reported in the needles of pines studied. Generally, the kinds of terpenes were similar but the relative amount of some compounds differed among the origins. The major components of the monoterpene fraction in Turkish sources were α-pinene (84.8%), β-pinene (4.1%) and limonene (3.0%), corresponding to 91.9% of the crude needle extract. In a PCA-analysis, 3-carene, myrcene and terpinolene in seedlings from Turkish provenances were quite low and thus, they were clearly different from a Northern European Scots pine provenance from Finland. In the resin acid fraction, abietic acid (62.4%) and dehydroabietic acid (16.1%) were the most abundant constituents in the needles of the Scots pine from Turkish provenances.     

华山松木蠹象聚集信息素分离鉴定和引诱效果

为了研制华山松木蠹象Pissodes punctatus Langor et Zhang的引诱剂,对华山松木蠹象的虫粪和雄虫后肠挥发性物质进行了分析鉴定和室内外生物活性测试。经GC-MS测定,发现在华山松木蠹象的新鲜虫粪和雄虫后肠挥发性物质中,除了松树挥发性的单萜烯如α-蒎烯、β-蒎烯和3-蒈烯以外,还存在1-甲基-2-异丙烯基-环丁烷乙醇（grandisol）。室内Y-型嗅觉仪趋向实验表明,较低浓度的3-（+）-蒈烯、1-甲基-2-异丙烯基-环丁烷乙醇及其相应的醛1-甲基-2-异丙烯基-环丁烷2醛（grandisal）,引起华山松木蠹象的正趋向反应。林间引诱试验表明,1-甲基-2-异丙烯基-环丁烷乙醇和1-甲基2-异丙烯基-环丁烷2醛对华山松木蠹象具有一定的引诱作用。由此推断,1-甲基-2-异丙烯基-环丁烷乙醇可能是华山松木蠹象的集结信息素成分之一。     

Manipulation of VOC emissions with methyl jasmonate and carrageenan in the evergreen conifer Pinus sylvestris and evergreen broadleaf Quercus ilex

Plant defence can be induced by exposing plants to the plant hormone jasmonic acid (JA) or its volatile ester, methyl jasmonate (MeJA). Carrageenans (Carr) - sulphated D-galactans extracted from red algae - can also induce plant defences. In this study, the effects of exogenous MeJA and Carr application (concentration 300 and 12.7 μmol, respectively) on volatile emissions from two widespread evergreen woody species, Pinus sylvestris (nine Turkish and one Finnish provenance) and Quercus ilex (Italian provenance) were investigated. We collected headspace samples from seedlings and analysed the quality and quantity of volatile compounds emitted by treated and control plants. In total, 19 monoterpenes, 10 sesquiterpenes, 10 green leaf volatiles (GLVs) and two aromatic compounds were emitted by P. sylvestris from all the provenances studied. Foliar MeJA application clearly affected the volatile profiles of trees from all the provenances. Effects of Carr were genotype specific. In Q. ilex, emissions of sesquiterpenes, GLVs and the homoterpene (E)-DMNT were all induced by MeJA application. However, emissions of most constitutively emitted monoterpenes were significantly reduced. Carr application also led to a significant reduction in monoterpene emissions, but without corresponding increases in other emissions. Our results indicate that exogenously applied MeJA and Carr can both significantly modify the volatile profiles of P. sylvestris and Q. ilex, but also that there are important provenance- and species-specific differences in the overall degree of elicitation and compositions of elicited compounds.     

Volatile flavour components of mango fruit

An essence of fresh Venezuelan mango fruit obtained by well-established procedures possessed the characteristic aroma of the fruit. It was analysed by GC/MS using both EI and Cl. The fruit produced a relatively small quantity of aroma volatiles (ca 60 μg/kg fresh fruit), less than that obtained from many similar tropical fruits. Terpene hydrocarbons comprised ca 68% of the sample, eight monoterpenes contributing ca 54% and four sesquiterpenes contributing ca 14%. Important constituents included α-pinene, car-3-ene, limonene, γ-terpinene, α-humulene, β-selinene, acetophenone, benzaldehyde and a dimethylstyrene. Car-3-ene (26%) was the major constituent, and on odour evaluation of separated components at an odour port during GC, the peak due to this compound was described as having an aroma of mango leaves. This compound has not previously been detected among mango volatiles. The only other component providing mango aroma was a dimethylstyrene, and this too is a new mango volatile.     

Chemical composition and antimicrobial activity of the essential oil of endemic Dalmatian black pine (Pinus nigra ssp. dalmatica)

The chemical composition and the antimicrobial activity of the essential oil isolated from the needles of endemic Dalmatian black pine (Pinus nigra ssp. dalmatica) from Croatia were investigated. The chemical composition of the essential oil was determined by GC and GC/MS analyses, and the main compounds identified were α-pinene, β-pinene, germacrene D, and β-caryophyllene. Disc-diffusion and broth-microdilution assays were used for the in vitro antimicrobial screening. The Dalmatian black pine essential oil exhibited a great potential of antibacterial activity against Gram-positive bacteria (MIC=0.03-0.50% (v/v)) and a less pronounced activity against Gram-negative bacteria (MIC=0.12-3.2% (v/v)). The volatile compounds also inhibited the growth of all fungi tested, including yeast.