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Fredrik Schlyter - One of the best experts on this subject based on the ideXlab platform.
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Interactions among Norway spruce, the bark beetle Ips typographus and its fungal symbionts in times of drought
Journal of Pest Science, 2021Co-Authors: Sigrid Netherer, Dineshkumar Kandasamy, Anna Jirosová, Blanka Kalinová, Martin Schebeck, Fredrik SchlyterAbstract:Resilience and functionality of European Norway spruce forests are increasingly threatened by mass outbreaks of the bark beetle Ips typographus promoted by heat, wind throw and drought. Here, we review current knowledge on Norway spruce and I. typographus interactions from the perspective of drought-stressed trees, host selection, colonisation behaviour of beetles, with multi-level effects of symbiotic ophiostomatoid fungi. By including chemo-ecological, molecular and behavioural perspectives, we provide a comprehensive picture on this complex, multitrophic system in the light of climate change. Trees invest carbon into specialised metabolism to produce defence compounds against biotic invaders; processes that are strongly affected by physiological stress such as drought. Spruce bark contains numerous terpenoid and phenolic substances, which are important for bark beetle aggregation and attack success. Abiotic stressors such as increased temperatures and drought affect composition, amounts and emission rates of volatile compounds. Thus, drought events may influence olfactory responses of I. typographus , and further the pheromone communication enabling mass attack. In addition, I. typographus is associated with numerous ophiostomatoid fungal symbionts with multiple effects on beetle life history. Symbiotic fungi degrade spruce toxins, help to exhaust tree defences, produce beetle semiochemicals, and possibly provide nutrition. As the various fungal associates have different temperature optima, they can influence the performance of I. typographus differently under changing environmental conditions. Finally, we discuss why effects of drought on tree-killing by bark beetles are still poorly understood and provide an outlook on future research on this eruptive species using both, field and laboratory experiments.
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Styrene, (+)-trans-(1R,4S,5S)-4-Thujanol and Oxygenated Monoterpenes Related to Host Stress Elicit Strong Electrophysiological Responses in the Bark Beetle Ips typographus
Journal of Chemical Ecology, 2019Co-Authors: Christian Schiebe, Goran Birgersson, C. Rikard Unelius, Suresh Ganji, Muhammad Binyameen, Fredrik SchlyterAbstract:Bark beetles kill apparently vigorous conifers during epidemics by means of pheromone-mediated aggregation. During non-endemic conditions the beetles are limited to use trees with poor defense, like wind-thrown. To find olfactory cues that help beetles to distinguish between trees with strong or weak defense, we collected volatiles from the bark surface of healthy felled or standing Picea abies trees. Furthermore, living trees were treated with methyl jasmonate in order to induce defense responses. Volatiles were analyzed by combined gas chromatography and electroantennographic detection (GC-EAD) on Ips typographus antennae. Compounds eliciting antennal responses were characterized by single sensillum recording for identification of specific olfactory sensory neurons (OSN). Release of monoterpene hydrocarbons decreased, while oxygenated compounds increased, from spring to early summer in felled trees. In both beetle sexes particular strong EAD activity was elicited by trace amounts of terpene alcohols and ketones. 4-Thujanol gave a very strong response and the absolute configuration of the tested natural product was assigned to be (+)- trans -(1 R, 4 S, 5 S )-thujanol by stereoselective synthesis and enantioselective gas chromatography. One type of OSN responded to all ketones and five other OSN were characterized by the type of compounds that elicited responses. Three new OSN classes were found. Of the eight EAD-active compounds found in methyl jasmonate-treated bark, the known anti-attractant 1,8-cineole was the one most strongly induced. Our data support the hypothesis that highly active oxygenated host volatiles could serve as positive or negative cues for host selection in I. typographus and in other bark beetles.
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specificity and redundancy in the olfactory system of the bark beetle Ips typographus single cell responses to ecologically relevant odors
Journal of Insect Physiology, 2009Co-Authors: Martin Andersson, Mattias C Larsson, Fredrik SchlyterAbstract:We screened 150 olfactory sensilla in single-sensillum recordings to unravel the mechanisms underlying host selection in the spruce bark beetle, Ips typographus (Coleoptera: Curculionidae: Scolytinae). Odor stimuli comprised of pheromone (various bark beetle spp.), host, and non-host compounds elicited strong and selective responses from 106 olfactory receptor neurons (ORNs), 45 of which were tuned to pheromone compounds, 37 to host compounds, and 24 to non-host volatiles (NHV). In addition, 26 ORNs responded only weakly to any odor stimulus. Strongly responding ORNs were classified into 17 classes. Seven classes responded primarily to the Ips pheromone compounds: cis-verbenol, Ipsenol, Ipsdienol (two classes), 2-methyl-3-buten-2-ol, amitinol, or verbenone, respectively. Six classes responded to the host compounds: a-pinene, myrcene, p-cymene, myrcene and p-cymene, 1,8-cineole, or D3-carene, respectively. Four classes responded to NHV: 3-octanol, 1-octen-3-ol, trans-conophthorin, or indiscriminately to the repellent green leaf volatiles (GLVs) 1-hexanol, Z3-hexen-1-ol and E2-hexen- 1-ol, respectively. Indiscriminate responses from GLV neurons might explain a behavioral redundancy among these GLVs. This is the first description of individual bark beetle ORNs dedicated to NHV perception. These comprise almost 25% of the strongly responding neurons, demonstrating that a large proportion of the olfactory system is devoted to signals from plants that the insect avoids. (Less)
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bark volatiles from nonhost angiosperm trees of spruce bark beetle Ips typographus l coleoptera scolytidae chemical and electrophysiological analysis
Chemoecology, 2000Co-Authors: Qinghe Zhang, Fredrik Schlyter, Goran BirgerssonAbstract:Volatiles from bark of three nonhost angiosperm trees of Ips typographus (Coleoptera: Scolytidae) (Betula pendula, B. pubescens, and Populus tremula) were collected by headspace sampling and direct solvent extraction in June 1998, and identified and quantified by coupled gas chromatographic-mass spectrometry (GC-MS). Only small amounts of bark volatiles were detected in the aerations in situ from undamaged stems of the nonhost trees. In headspace volatiles from bark chIps the two birch species had a similar odour profile, with two sesquiterpene hydrocarbons, α-zingiberene and α-santalene, as the most dominant components. Bark of P. tremula emitted significantly less sesquiterpenes and more green leaf volatiles (GLVs) than the two birch species did. Solvent extraction of fresh bark gave similar volatile composition for the two birches compared to the headspace of bark chIps, but large differences were found in P. tremula. Coupled gas chromatographic-electroantennographic detection analysis (GC-EAD) of the headspace volatiles from fresh bark chIps of the three nonhost species revealed five compounds that consistently elicited antennal responses by I. typographus. The strongest antennal responses were elicited by trans-conophthorin, (5S,7S)-(–)-7-methyl-1,6-dioxaspiro[4.5]decane with optical purity of ca. 90% (S,S). The other four antennally active bark volatiles were 1-hexanol, (Z)-3-hexen-1-ol, 3-octanol and 1-octen-3-ol, which had similar electroantennogram (EAG) dose-response curves and response thresholds. (±)-trans-Conophthorin showed a different, linear EAG dose-response curve, with a 10 times lower response threshold than the other GC-EAD active compounds, similar to the pheromone component, (−)-(4S)-cis-verbenol. These results suggest that not only the green leaf alcohols from leaves of the angiosperm trees but also the nonhost bark volatiles could be used by I. typographus as long-range olfactory cues to discriminate between its conifer host and the nonhosts, birch and aspen.
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green leaf volatiles interrupt pheromone response of spruce bark beetle Ips typographus
Journal of Chemical Ecology, 1999Co-Authors: Qinghe Zhang, Fredrik Schlyter, Peter AndersonAbstract: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.
Rastislav Jakuš - One of the best experts on this subject based on the ideXlab platform.
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storms temperature maxima and the eurasian spruce bark beetle Ips typographus an infernal trio in norway spruce forests of the central european high tatra mountains
Agricultural and Forest Meteorology, 2017Co-Authors: Pavel Mezei, Josef Pennerstorfer, Rastislav Jakuš, Jaroslav Skvarenina, Maria Havasova, Jan Ferencik, Jan Slivinský, Svetlana Bicarova, Dusan BilcikAbstract:Abstract Norway spruce forests ( Picea abies Karst.) of the Carpathian High Tatra Mountains have been subject to unprecedented tree mortality caused by attacks of the Eurasian spruce bark beetle ( Ips typographus L.) in recent decades. The outbreaks were preceded and accompanied by wind throw events and periods of increased seasonal temperature. We obtained climatic data and data on tree mortality due to storm throw and bark beetles by using a combination of direct dead tree inventory and remote sensing techniques, and examined annual tree loss change over a 26-year period in a forest district of the Slovak High Tatra National Park. In particular, we found that the combination of the previous year’s maximum daily temperature sum, tree mortality caused by wind, and bark beetle-caused tree mortality best explained the annual tree loss change in nonlinear regression models. The number of trees infested by bark beetles clearly increased with maximum air temperature sums ranging from 2850 to 3150 ° days, but declined below or above this thermal optimum. Annual tree mortality clearly increased subsequent to years associated with seasonal temperature sums allowing for the development of sister broods. Given consistently favourable future climatic conditions for development of I. typographus populations in the study area, a possible shift from the now predominantly uni-voltine to multi-voltine bark beetle populations might increase attack pressure also at high elevation sites.
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host and site factors affecting tree mortality caused by the spruce bark beetle Ips typographus in mountainous conditions
Forest Ecology and Management, 2014Co-Authors: Pavel Mezei, Miroslav Blaženec, Rastislav Jakuš, Wojciech Grodzki, Jaroslav Skvarenina, Veronika BrandýsovaAbstract:Abstract To better understand the initiation and severity of tree mortality caused by the spruce bark beetle (Ips typographus (L.)) during an outbreak, we analysed the entire course of an outbreak from 1990 to 2000 in the Tatra Mountains (Western Carpathians, Central Europe). This time period represents the last complete bark beetle gradation in this area. We distinguished three outbreak phases: the incipient epidemic, epidemic and post-epidemic stages. The sampling unit was the forest subcompartment. We analysed a total of 315 forest subcompartments over more than 2000 ha. We investigated the influence of 11 environmental and stand variables on two processes in different phases of the outbreak: the initiation and the severity of spruce mortality. We used factor analysis, discriminant analysis, multiple linear regressions and boosted regression trees for the statistical analyses. The results showed that the roles of host and site factors in the initiation and severity of spruce mortality caused by the spruce bark beetle differed during the outbreak according to the exploitation of available host resources. The initiation of tree mortality was primarily related to host factors, and the severity of mortality was dependent on host size and insolation.
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effect of limonene and 1 methoxy 2 propanol on Ips typographus response to pheromone blends
Journal of Forestry Research, 2009Co-Authors: Miroslav Blaženec, Rastislav JakušAbstract:We compared two different strategies to increase the catches of Ips typographus (L.), particularly males, in pheromone-baited traps. The first of these strategies, the barrier approach, used alternating pheromone blends, targeting males and females respectively, in closely-spaced traps forming a barrier around forest stands. The second strategy, the single trap approach, used widely-spaced traps that were all baited with the same lure and intended to trap the highest possible numbers of males without compromising trapping of females. In the blend used for the barrier traps targeting primarily males, with a lower percentage of (4S)-cis-verbenol (cV), the (−)-α-pinene was replaced step wise with (+)-limonene at rates of 0%, 1%, 10%, 35%, 60% and 90%. This replacement had no significant effect on the numbers of responding I. typographus males, but there was a slight effect on the percentage of males caught. In the attractant blend for the barrier traps targeting females, with a higher percentage of cV, the 2-methyl-3-buten-2-ol (MB) was replaced with 1-methoxy-2-propanol (MP) in a similar fashion as for the male-specific blends. The replacement did not significantly affect the catch of females. Thus, it is possible to use the MP in the blend with cV and Ipsdienol without significant change in catch efficacy. In the blends for single traps, the (−)-α- pinene was replaced with (+)-limonene and MB with MP. The replacement of (−)-α-pinene had only a slight effect on the percentage of males, but the results suggest that replacing MB with MP in the blend will not significantly reduce trapping efficacy.
Marco Heurich - One of the best experts on this subject based on the ideXlab platform.
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european spruce bark beetle Ips typographus l green attack affects foliar reflectance and biochemical properties
International Journal of Applied Earth Observation and Geoinformation, 2018Co-Authors: Roshanak Darvishzadeh, Haidi Abdullah, Andrew K Skidmore, T A Groen, Marco HeurichAbstract:Abstract The European spruce bark beetle Ips typographus, L. (hereafter bark beetle), causes major economic loss to the forest industry in Europe, especially in Norway Spruce ( Picea abies ). To minimise economic loss and preclude a mass outbreak, early detection of bark beetle infestation (so-called “green attack” stage – a period at which trees are yet to show visual signs of infestation stress) is, therefore, a crucial step in the management of Norway spruce stands. It is expected that a bark beetle infestation at the green attack stage affects a tree’s physiological and chemical status. However, the concurrent effect on key foliar biochemical such as foliar nitrogen and chlorophyll as well as spectral responses are not well documented in the literature. Therefore, in this study, the early detection of bark beetle green attacks is investigated by examining foliar biochemical and spectral properties (400–2000 nm). We also assessed whether bark beetle infestation affects the estimation accuracy of foliar biochemicals. An extensive field survey was conducted in the Bavarian Forest National Park (BFNP), Germany, in the early summer of 2015 to collect leaf samples from 120 healthy and green attacked trees. The spectra of the leaf samples were measured using an ASD FieldSpec3 equipped with an integrating sphere. Significant differences (p
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spatio temporal infestation patterns of Ips typographus l in the bavarian forest national park germany
Ecological Indicators, 2013Co-Authors: Angela Lausch, Marco Heurich, Lorenz FahseAbstract:Abstract The Bavarian Forest National Park in Germany has experienced infestations of bark beetle ( Ips typographus L.) since the 1980s, resulting in considerable ecological loss due to the destruction of almost 5800 ha of spruce forests. Although there have been numerous investigations on the physiology and ecology of the bark beetle, until now the spatio-temporal infestation and dispersal dynamics of the bark beetle over a longer period have still not been satisfactorily understood. The understanding of the structure and the dispersal of bark beetle infestations is however of significant importance for forest management systems in order to predict the risk of outbreaks, especially in the face of climate change. The aim of this investigation was therefore (I) to analyse and describe the long term spatio-temporal infestation patterns of I. typographus in the Bavarian Forest National Park, Germany on the landscape scale, (II) to conduct investigations on spatio-temporal shifts of the focal points of bark beetle infestations from 1988 to 2010 and (III) to compare the quantitative spatio-temporal infestation patterns obtained at the landscape level with the dispersal patterns of the spatially explicit agent-based simulation model (SAMBIA) for I. typographus ( Fahse and Heurich, 2011 ). The results of the study show that a shift in the infestation pattern of I. typographus from 1988 to 2010 occurs at different time intervals both undirectionally as well as directionally. Furthermore, the dispersal pattern of the bark beetle was recorded quantitatively and described extensively over a period of 23 years on the landscape scale. The quantification of the presence and dispersion pattern of I. typographus in the Bavarian Forest National Park allows us to gain a better understanding of the distribution pattern of the bark beetle on the landscape scale. In this way, both the pattern and structure of infestation patterns obtained for I. typographus serve as: (a) a basis for the criteria to improve the parameters of spatio-temporal simulation models, (b) a better understanding of the bark beetle pattern and existing processes such as disturbance patterns or damage patterns in the food web of spruces due to climate change, (c) a test for the hypotheses on the relationshIps between the presence of bark beetle and relevant habitat variables as well as (d) the compilation of forecast models on the dispersal of bark beetle. These predictions can help with the implementation of specific management strategies to prevent the dispersal of bark beetle.
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progress of forest regeneration after a large scale Ips typographus outbreak in the subalpine picea abies forests of the bavarian forest national park
2009Co-Authors: Marco HeurichAbstract:The Bavarian Forest National Park is the oldest National Park in Germany. The overall management concept within the park is the protection of unaltered natural processes. The outbreak of a spruce bark beetle (Ips typographus) infestation in 1993 has especially affected the subalpine range of the park with its high proportion of spruce trees. This paper describes a study on how forest regeneration was affected by the process of the large-scale die off of forest trees. For this purpose, surveys from a total of 572 samples from the years 1991, 1996, 1998, 2000, and 2005 were available. Compared to 1991, when the regeneration density was 978 trees per hectare, it had increased to 4502 trees per hectare in 2005. The distribution of the regeneration has also changed. While in 1998, only 36.7% or the inventory plots were found to have a density of greater than 1000 plants per hectare, this value had increased to 62.4% by 2005. No regeneration was found in only 0.9% of the inventory plots. Regeneration consisted mostly of Norway spruce (89.0%) and mountain ash (7.9%). European beech (1.9%) and all other tree species (1.2%) were much less significant. In addition, the proportion of tree heights has clearly shifted to taller trees. This indicates a favourable development of the trees in the regeneration. The proportion of trees damaged by browsing ungulates was 1.6%. Browsing damage to mountain ash was relatively high at 33.6%. Other forms of damage were relatively insignificant.
Qinghe Zhang - One of the best experts on this subject based on the ideXlab platform.
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bark volatiles from nonhost angiosperm trees of spruce bark beetle Ips typographus l coleoptera scolytidae chemical and electrophysiological analysis
Chemoecology, 2000Co-Authors: Qinghe Zhang, Fredrik Schlyter, Goran BirgerssonAbstract:Volatiles from bark of three nonhost angiosperm trees of Ips typographus (Coleoptera: Scolytidae) (Betula pendula, B. pubescens, and Populus tremula) were collected by headspace sampling and direct solvent extraction in June 1998, and identified and quantified by coupled gas chromatographic-mass spectrometry (GC-MS). Only small amounts of bark volatiles were detected in the aerations in situ from undamaged stems of the nonhost trees. In headspace volatiles from bark chIps the two birch species had a similar odour profile, with two sesquiterpene hydrocarbons, α-zingiberene and α-santalene, as the most dominant components. Bark of P. tremula emitted significantly less sesquiterpenes and more green leaf volatiles (GLVs) than the two birch species did. Solvent extraction of fresh bark gave similar volatile composition for the two birches compared to the headspace of bark chIps, but large differences were found in P. tremula. Coupled gas chromatographic-electroantennographic detection analysis (GC-EAD) of the headspace volatiles from fresh bark chIps of the three nonhost species revealed five compounds that consistently elicited antennal responses by I. typographus. The strongest antennal responses were elicited by trans-conophthorin, (5S,7S)-(–)-7-methyl-1,6-dioxaspiro[4.5]decane with optical purity of ca. 90% (S,S). The other four antennally active bark volatiles were 1-hexanol, (Z)-3-hexen-1-ol, 3-octanol and 1-octen-3-ol, which had similar electroantennogram (EAG) dose-response curves and response thresholds. (±)-trans-Conophthorin showed a different, linear EAG dose-response curve, with a 10 times lower response threshold than the other GC-EAD active compounds, similar to the pheromone component, (−)-(4S)-cis-verbenol. These results suggest that not only the green leaf alcohols from leaves of the angiosperm trees but also the nonhost bark volatiles could be used by I. typographus as long-range olfactory cues to discriminate between its conifer host and the nonhosts, birch and aspen.
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green leaf volatiles interrupt pheromone response of spruce bark beetle Ips typographus
Journal of Chemical Ecology, 1999Co-Authors: Qinghe Zhang, Fredrik Schlyter, Peter AndersonAbstract: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.
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leaf volatiles from nonhost deciduous trees variation by tree species season and temperature and electrophysiological activity in Ips typographus
Journal of Chemical Ecology, 1999Co-Authors: Qinghe Zhang, Goran Birgersson, Christer Lofstedt, Jan Lofqvist, Fredrik SchlyterAbstract:The leaf volatiles emitted from four nonhost tree species of Ips typographus, i.e. Betula pendula, B. pubescens, Populus tremula, and Sambucus nigra, were collected outdoors by headspace sampling in situ and analyzed by GC-MS. Three major classes of compounds, aliphatics [mainly green-leaf volatiles (GLVs)], monoterpenes, and sesquiterpenes, existed in all the deciduous tree species investigated. In June, when the bark beetles are searching in flight for host trees, GLVs mainly consisting of (Z)-3-hexenyl acetate and (Z)-3-hexen-1-ol were the dominant constituents in B. pendula and S. nigra. In B. pubescens and P. tremula, sesquiterpenes (and their derivatives) and monoterpenes made up the major part of whole volatile blends, respectively. Surprisingly, sesquiterpene alcohols and other oxides released from B. pubescens in considerable amounts were not found in the closely related species, B. pendula. By August, both the total volatiles and individual compounds significantly decreased, mainly due to the maturation of leaves, since the light intensity and temperatures during sampling were the same as in June. There were almost no volatiles detected from P. tremula and S. nigra leaves in August. The total emissions from these deciduous species were significantly different among the species, with B. pubescens releasing 5–10 times more than other species. Under the conditions of constant light intensity and humidity, emissions of both total volatiles and most individual components of severed B. pendula and S. nigra branches (with fresh leaves) increased according to a saturation curve from 16°C to 40°C. Ips typographus antennae responded strongly to green leaf alcohols: (Z)-3-hexen-1-ol, 1-hexanol, and (E)-2-hexen-1-ol, but not to aldehydes or acetates in GC-EAD analyses of B. pendula and B. pubescens leaf volatiles. No antennal responses to monoterpenes, sesquiterpenes, or sesquiterpene oxides were found. These three antennally active GLVs emitted from nonhost tree leaves might be indicators of a wrong habitat in the host selection of conifer bark beetles.
Hannu Hyyppa - One of the best experts on this subject based on the ideXlab platform.
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the potential of dual wavelength terrestrial lidar in early detection of Ips typographus l infestation leaf water content as a proxy
Remote Sensing of Environment, 2019Co-Authors: Samuli Junttila, Markus Holopainen, Mikko Vastaranta, Paivi Lyytikainensaarenmaa, Harri Kaartinen, Juha Hyyppa, Hannu HyyppaAbstract:Abstract Climate change is causing novel forest stress around the world due to changes in environmental conditions. Forest pest insects, such as Ips typographus (L.), are spreading toward the northern latitudes and are now able to produce more generations in their current range; this has increased forest disturbances. Timely information on tree decline is critical in allowing forest managers to plan effective countermeasures and to forecast potential infestation areas. Field-based infestation surveys of bark beetles have traditionally involved visual estimates of entrance holes, resin flow, and maternal-gallery densities; such estimates are prone to error and bias. Thus, objective and automated methods for estimating tree infestation status are required. In this study, we investigated the feasibility of dual-wavelength terrestrial lidar in the estimation and detection of I. typographus infestation symptoms. In addition, we examined the relationship between leaf water content (measured as gravimetric water content and equivalent water thickness) and infestation severity. Using two terrestrial lidar systems (operating at 905 nm and 1550 nm), we measured 29 mature Norway spruce (Picea abies [L.] Karst.) trees that exhibited low or moderate infestation symptoms. We calculated single and dual-wavelength lidar intensity metrics from stem and crown points to test these metrics' ability to discriminate I. typographus infestation levels using regressions and linear discriminant analyses. Across the various I. typographus infestation levels, we found significant differences (p
