135,372 research outputs found
2-methyl-3-buten-2-ol: a pheromone component of conifer bark beetles found in the bark of nonhost deciduous trees
No full textVolatiles from bark of aspen,Populus tremulaL. and two species of birch: silver birch (Betula pendulaRoth.) and common birch (B. pubescensEhrh.), were collected by direct solvent extraction and aeration of both newly cut bark chips and undamaged stems in June 1998 and subjected to GC-MS analysis. The results showed the presence of 2-methyl-3-buten-2-ol (MB), one of the two principal aggregation pheromone components of the spruce bark beetle,Ips typographus, in bark extraction samples of all the three deciduous tree species tested. In addition, one more oxygenated hemiterpene, 3-methyl-3-buten-2-one, and (E)-3-penten-2-ol were also found in the bark extracts. Only trace amounts of MB were detected in some aeration samples of the fresh bark chips, and no MB was found from the aeration samples of undamaged stems at detectable levels. The occurrence of this compound was also confirmed in the bark of four exotic birch species:B. albosinensisSchneid.,B. ermaniiCham.,B. jacquemontiiSpach, andB. maximowiczianaRegel, but not yet in the European pines/spruces and the common yeasts. Our results raise major questions regarding the evolution, the tropospheric chemistry, and the ecological role of this hemiterpene alcohol. They also suggest that comparative studies on the biosynthetic pathways for MB in different sources would be of considerably evolutionary interest
Population dynamics of tree-killing bark beetles
No full textDuring outbreak periods, the European spruce bark beetle and the North American mountain pine beetle are able to kill millions of coniferous trees. Throughout the 20th century, six outbreaks have occurred in Sweden and four in British Columbia, with about 20-year intervals in both regions. The outbreaks of the mountain pine beetles seem to grow much larger and last longer compared to the outbreaks of the spruce bark beetles. Over the years, the mountain pine beetle has killed about 60 million ha forest or 550 million m3 trees in British Columbia, which is at least one hundred times more than for the Spruce bark beetle in Sweden. Damages of both species have increased markedly in the last forty years. About 750 spruce bark beetles per m2 are necessary to kill a healthy spruce, whereas seven times fewer, i.e., about 110 mountain pine beetles per m2, are needed to kill a healthy pine. Furthermore, twice as many offspring per m2 bark are produced by the spruce bark beetle compared to the mountain pine beetle. An explanation for the large differences in population dynamics between these two beetle species may spring from differences in (1) the availability of host trees, (2) number of specimens required to kill a tree, and (3) reproductive success. The latter is in turn affected by the intraspecific competition, nutrient content, and occurrence of fungi
Induced terpene accumulation in Norway spruce inhibits bark beetle colonization in a dose-dependent manner
No full textBackground: Tree-killing bark beetles (Coleoptera, Scolytinae) are among the most economically and ecologically important
forest pests in the northern hemisphere. Induction of terpenoid-based oleoresin has long been considered important in
conifer defense against bark beetles, but it has been difficult to demonstrate a direct correlation between terpene levels and
resistance to bark beetle colonization.
Methods: To test for inhibitory effects of induced terpenes on colonization by the spruce bark beetle Ips typographus (L.) we
inoculated 20 mature Norway spruce Picea abies (L.) Karsten trees with a virulent fungus associated with the beetle,
Ceratocystis polonica (Siem.) C. Moreau, and investigated induced terpene levels and beetle colonization in the bark.
Results: Fungal inoculation induced very strong and highly variable terpene accumulation 35 days after inoculation. Trees
with high induced terpene levels (n = 7) had only 4.9% as many beetle attacks (5.1 vs. 103.5 attacks m22) and 2.6% as much
gallery length (0.029 m m22 vs. 1.11 m m22) as trees with low terpene levels (n = 6). There was a highly significant rank
correlation between terpene levels at day 35 and beetle colonization in individual trees. The relationship between induced
terpene levels and beetle colonization was not linear but thresholded: above a low threshold concentration of ,100 mg
terpene g21 dry phloem trees suffered only moderate beetle colonization, and above a high threshold of ,200 mg terpene
g21 dry phloem trees were virtually unattacked.
Conclusion/Significance: This is the first study demonstrating a dose-dependent relationship between induced terpenes
and tree resistance to bark beetle colonization under field conditions, indicating that terpene induction may be
instrumental in tree resistance. This knowledge could be useful for developing management strategies that decrease the
impact of tree-killing bark beetles
The spruce bark beetle Ips typographus in a changing climate
No full textOutbreaks of the Spruce bark beetle Ips typographus are often triggered by storm and drought and have destroyed millions of cubic meters of wood. It is therefore a pest insect of economic importance in Europe. Breeding underneath the bark of Norway spruce Picea abies, I. typographus brings blue-stain fungi into the wood which strangles the water uptake and lowers the timber quality. I. typographus (Coleoptera; Scolytinae) and other insects are dependent on the temperature for their metabolism and development. In a future warmer climate we may see increased storm frequencies with larger windthrows serving more breeding material for bark beetles. Further, a higher mean temperature allowing earlier onset of flight of spruce bark beetle in spring, and a faster development from egg to adult, will increase the probability of a second swarming period during the summer and production of a 2nd generation. In a warmer climate higher evaporation will lead to water shortage and increased host susceptibility, especially later during the summer. Thus, an extended (2nd) flight period may lead to more damage to spruce forests. Two generations of the spruce bark beetle is the rule in lower altitude areas of central Europe and in a future climate bivoltinistic behavior is predicted to become more common also in higher altitudes and northward in Scandinavia
Study of the decay mechanism for B+ -> p(p)over-barK(+) and B+ -> p(p)over-bar pi(+)
No full textWe study the characteristics of the low mass p (p) over bar enhancements near threshold in the three-body decays B+ -> p (p) over barK(+) and B+ -> p (p) over bar pi(+). We observe that the proton polar angle distributions in the p (p) over bar helicity frame in the two decays have the opposite polarity, and measure the forward-backward asymmetries as a function of the p mass for the p (p) over barK(+) mode. We also search for the intermediate two-body decays, B+ -> (p) over bar Delta(++) and B+ -> p (Delta) over bar (0), and set upper limits on their branching fractions. These results are obtained from a 414 fb(-1) data sample that contains 449 x 10(6) B (B) over bar events collected near the Gamma(4S) resonance with the Belle detector at the KEKB asymmetric-energy e(+)e(-) collider. (c) 2007 Elsevier B.V. All rights reserved.IPE
Olfaction in the Spruce Bark Beetle, Ips typographus
No full textThe bark beetle Ips typographus regularly kills spruce trees in the Palearctic. Spruces are colonized by means of attraction to an aggregation pheromone. Attraction is modulated by anti-attractive volatiles (NHV) from non-host plants. In this thesis, olfaction in I. typographus was studied. At the molecular level, putative odorant receptors (ORs) were identified. When compared with OR sequences of Tribolium castaneum, a drastic extension of bark beetle OR function was indicated. The ORs are situated in the membrane of olfactory receptor neurons (ORNs). By recording odor responses from these neurons, 17 ORN classes that strongly responded to pheromone, host, and non-host compounds, were characterized. Surprisingly, al¬most 25 % of these responded to anti-attractive NHV. The ORN for the essential pheromone compound cis-verbenol (cV), was in some sensilla co-localized with an ORN for the host plant compound 1,8-cineole (Ci). Ci inhibited pheromone attraction in the field. In addition, while the ORN for Ci responded, the response in the co-localized cV ORN was inhibited, indicating interactions between ORNs. In electrophysiological studies of olfaction, odor stimuli are often based on a known amount of compound put on a filter paper, but the amount in the vapor phase (the actual stimulus) is unknown. Using a photoionization detector, vapor amounts of compounds released from stimulus cartridges were measured. A large variation between compounds, solvents, and successive stimulations were recorded. This indicated that stimulus doses often must be corrected for differences in volatility, and that consistent test protocols are required. In nature, insects orient in semiochemically diverse habitats with intermixing odor plumes. We studied the attraction to separated pheromone components, and pheromone and anti-attractant sources in the bark beetle and in the moth Spodoptera littoralis. While the beetle responded to spacing distances of a few decimeters, the moth responded to only a few centimeters. This may reflect different processing mechanisms in the sex pheromone system of the moth as compared to the aggregation pheromone system of the beetle. In addition, a long-distance (at least 2 m) effect of NHV was found, indicating a potential for these anti-attractants in forest protection against the beetle
Dead wood retention and the risk of bark beetle attack
No full textWind-felled Norway spruce trees left for conservation purposes and spruce stems stored as forest fuel may be colonised by the bark beetles Ips typographus and Pityogenes chalcographus (Coleoptera: Scolytidae). The risk of nearby living trees being attacked and killed by these species was experimentally investigated at stand edges bordering fresh clearcuts. Attack by I. typographus was studied at edges of mature spruce with one, five or no cut trees. Attack by P. chalcographus was studied within plots on edges of young spruce. The plots contained piles of cut young trees, or no piles. Number of trees killed by I. typographus did not differ between edges with and without cut trees, or between edges with one and five cut trees. Tree-killing was more frequent close (<20 m) to felled trees than elsewhere on the edges, suggesting that felled trees provide focal points for attacks within edges. The piles increased the risk of P. chalcographus attack, but almost no attacked tree was killed. Attacks were associated with pile colonisation, whereas emergence by the new generation beetles did not increase the risk of attack. Previous studies have shown a high reproductive success of I. typographus in felled trees after storms and a low success in standing trees killed during outbreaks. Here, the success was compared in pairs of colonised cut trees and standing killed trees at a time with no outbreak and relatively few felled trees available in the landscape. The success in killed standing trees was (a) significantly higher than in cut trees, and (b) high enough to suggest that killed standing trees can contribute substantially to the area-wide production of beetles. The ability of P. chalcographus to kill trees and reproduce in them has previously been little studied. Here, attacks on living trees were induced by baiting trees with pheromone dispensers. The tree-killing ability was low. Reproductive success in killed trees was generally low, but was significantly higher in trees also attacked by I. typographus
The Molecular Weight Characterisation of Pinus radiata Bark Condensed Tannins
No full textCrude condensed tannins extracted from Pinus radiata bark (sourced from Tokoroa) with various solvents (Hot water (HW), methanol/water/acetic acid (MWA), acetone/water (AW) and hot aqueous 2% sulphite/urea solution (SFU)) were subjected to Sephadex LH-20 column chromatography to purify the condensed tannins by removing carbohydrate and flavonoid components (crude extracts were approximately 70% condensed tannins). The condensed tannins from the HW and MWA extractions were then fractionated on a Sephadex LH-20 column using a stepwise gradient of methanol, water and acetone to separate the condensed tannins according to molecular weight (MW). Fractions were collected and pooled to give eight final fractions (HW 1-8 and MWA 1-8). Purified and fractionated condensed tannin fractions were then analysed with a range of techniques including 1H nuclear magnetic resonance (NMR) spectroscopy, acid/phloroglucinol depolymerisation coupled with high performance liquid chromatography (HPLC) with UV and MS detection, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS), electrospray ionisation mass spectrometry (ESI-MS) and gel permeation chromatography (GPC).
In the MALDI-TOF MS spectrum of the crude extracts the most intense signal was typically the tetramer peak and the decamer was typically the largest oligomer detected. In the spectra of late-eluting column fractions (i.e. HW and MWA 5-7) oligomers greater than the nonamer (DP up to 14) were detected and the most intense signal was shifted from the tetramer to higher MW oligomers. ESI MS showed itself to be better at analysing small MW condensed tannins. The MS results demonstrated that prior separation of the condensed tannins was effective in improving MS detection of higher MW oligomers.
The mDP of the crude and fractionated fractions was obtained by depolymerisation/HPLC. The mean degree of polymerisation (mDP) of the purified condensed tannins ranged between 7.3 (AW) and 9.2 (SFU). The mDP of the fractionated condensed tannins ranged between 2 and 18. The depolymerisation/HPLC results of the fractionated condensed tannins were used to construct a GPC calibration curve of condensed tannin MW versus GPC retention time. To identify the GPC dimer peak a procyanidin dimer was synthesised by reacting condensed tannins with catechin under acidic conditions. Through the use of various NMR techniques (DEPT135, COSY, HSQC and HMBC experiments) the synthetic dimer was characterised and the 1H and 13C NMR spectra fully assigned. The GPC calibration curve enabled MW profiles for the HW and MWA 2-8 fractions and crude extracts to be obtained. GPC analysis confirmed the presence of larger oligomers that were not detected by MALDI-TOF MS and ESI MS. GPC number average MW results were in agreement with the average MW results obtained from depolymerisation/HPLC results.
Pinus radiata bark condensed tannins from two different geographical locations (Golden Downs (Nelson) and Waimate (South Canterbury)) and different tree heights (0, 10 and 20 m) were analysed using the techniques described above to discover if there was any variability between samples. Trends that were observed between the different condensed tannins were decreases in condensed tannin yield and mDP as bark was obtained from higher up a tree. Extracts from New Zealand native bark (totara, rimu and kauri) were also analysed, showing that Rimu was the only bark of these species that contained significant amounts of condensed tannins. Overall this research has provided additional information on the structure and MW of P. radiata condensed tannins
Seasonal flight patterns of the Spruce bark beetle (Ips typographus) in Sweden
No full textThe major bark beetle threat to Norway spruce (Picea abies (L.) Karst.) in Eurasia is the spruce bark beetle Ips typographus. Beetles cause damage after population build-up in defenseless trees. To minimize attacks, timely removal of these trees is important. This is practiced by clearing of wind throws and sanitation felling. Thus, knowledge about the region-specific flight pattern and voltinism of I. typographus is necessary for efficient pest management.
This thesis focuses on the flight initiation and the variation in flight pattern of I. typographus over the season, which we have studied using pheromone traps during a seven year period in Sweden. Additionally, logs, that became colonized, were used to determine thermal sums required for the re-emergence of parental beetles and the emergence of filial beetles in southern Sweden.
Swarming began in the end of April (51 degree-days (dd) >5°C; daytime temp. >18°C). More than 50% of the flight activity occurred after mid-June and it continued until mid-August. That is a longer flight period than has been recorded previously. At least partly, this discrepancy with previous observations may be explained by our results that the temperature requirement for flight commencement is fulfilled more than two weeks earlier now than 30 years ago.
Re-emergence of parental beetles from the first brood started in the end of May (122 dd >5°C). A much higher proportion of parental beetles had re-emerged from trees colonized in May (95%) compared to in June (60%) or July (20%). This verifies that sister broods is an important part of the beetles' reproductive biology. The high proportion of beetles that re-emerged together with a significant continued beetle flight and oviposition showed that a high proportion of the beetles initate at least one sister brood.
Filial beetles began to emerge in the end of June (437 dd >5°C) and were caught in flight traps in early July and at least a partial second generation was started in each year. A much higher proportion of filial beetles had emerged from trees colonized in May (75%) than in June (50%) and July (15%).
We have shown that the temperature requirement for flight initiation are met earlier in the present climate which gives more time for the development of several sister broods and a potential second generation. This together with an expected increase in severe storm fellings indicates that the need for efficient pest management will increase with time. Timely removal of wind-felled trees is the main pest management option and in this thesis I present results of when the critical time periods occurs
Inbreeding and selection on sex ratio in the bark beetle Xylosandrus germanus
No full textBackground: Local Mate Competition (LMC) theory predicts a female should produce a more female-biased sex ratio if her sons compete with each other for mates. Because it provides quantitative predictions that can be experimentally tested, LMC is a textbook example of the predictive power of evolutionary theory. A limitation of many earlier studies in the field is that the population structure and mating system of the studied species are often estimated only indirectly. Here we use microsatellites to characterize the levels of inbreeding of the bark beetle Xylosandrus germanus, a species where the level of LMC is expected to be high. Results: For three populations studied, genetic variation for our genetic markers was very low, indicative of an extremely high level of inbreeding (F-IS = 0.88). There was also strong linkage disequilibrium between microsatellite loci and a very strong genetic differentiation between populations. The data suggest that matings among non-siblings are very rare (3%), although sex ratios from X. germanus in both the field and the laboratory have suggested more matings between non-sibs, and so less intense LMC. Conclusions: Our results confirm that caution is needed when inferring mating systems from sex ratio data, especially when a lack of biological detail means the use of overly simple forms of the model of interest.Peer reviewe
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