@article {10911,
	title = {Conifer phenolic resistance markers are bark beetle antifeedant semiochemicals},
	journal = {Agricultural and Forest Entomology},
	volume = {9},
	number = {3},
	year = {2007},
	month = {August},
	pages = {237-245},
	abstract = {Phenols are important in conifer resistance to fungi associated with bark beetles and as markers for resistance to beetle mass-attacks. However, the mechanism of phenolic activity in conifer resistance to Ips typographus bark beetle remains unclear. By a new bioassay, we tested the effect on host acceptance and tunnelling of male and female L typographus in an artificial gallery (13 mm long) for 4 h (no-choice test). To the artificial diet, an aliquot of host (catechin, taxifolin, or resveratrol) or nonhost (E-conophthorin) compounds was added, singly tested at doses close to those of tree bark. Host acceptance and tunnelling was measured by the amount of diet removed by the insects. All tested chemicals decreased the tunnelling activity of L typographus, with an antifeedant effect stronger in males and increasing with dose. No mortality was recorded. The nonhost volatile spiroketal, E-conophthorin, had the highest antifeedant activity both in males and females. Among host compounds, effects and dose-response were weak in females. Both catechin and E-conophthorin gave a 50\% reduction of tunnelling at a concentration of 0.1\% for males, the pioneering (host selecting) sex in Ips. The threshold of activity for host compounds to males was at concentrations of 0.03-0.1\%, which corresponds to, or is less than, the concentrations reported from spruce host bark. The results allow us to support the hypothesis of a direct behavioural antifeedant mechanism for resistance from those phenols that are particularly active for the pioneering males during tree attack},
	keywords = {Ips typographus},
	isbn = {1461-9555},
	author = {Faccoli, Massimo and Schlyter, Fredrik}
}
@article {10883,
	title = {Antifeedants and feeding stimulants in bark extracts of ten woody non-host species of the pine weevil, Hylobius abietis},
	journal = {Journal of Chemical Ecology},
	volume = {34},
	number = {10},
	year = {2008},
	month = {October},
	pages = {1290-1297},
	type = {Article},
	abstract = {Bark of ten woody species, known to be rejected as a food source by the pine weevil, Hylobius abietis, were sequentially extracted by a Soxhlet apparatus with pentane followed by methanol. Species were alder (Alnus glutinosa), aspen (Populus tremula), beech (Fagus sylvatica), guelder rose (Viburnum opulus), holly (Ilex aquifolium), horse chestnut (Aesculus hippocastanum), lilac (Syringa vulgaris), spindle tree (Evonymus europaeus), walnut (Juglans regia), and yew (Taxus baccata). Bark of each species was collected in southern Scandinavia during the summer. Resulting extracts were tested for antifeedant activity against the pine weevil by a micro-feeding choice assay. At a dose corresponding to that in the bark, methanol extracts from Aesculus, Taxus, Ilex, and Populus were antifeedant active, while pentane extracts of Aesculus, Fagus, Syringa, and Viburnum were stimulatory. Four known antifeedants against H. abietis, the straight-chained carboxylic acids, hexanoic and nonanoic acid (C6 and C9), carvone, and carvacrol were identified by gas chromatography (GC)-mass spectrometry (MS) in several extracts. The major constituents were identified and tested for feeding deterrence. The aromatic compounds benzyl alcohol and 2-phenylethanol are new non-host plant-derived feeding deterrents for the pine weevil. Additionally, two feeding stimulants, [beta]-sitosterol and 5-(hydroxymethyl)-2-furaldehyde, were identified. One active methanol extract of Aesculus bark was sequentially fractionated by liquid chromatography, and major compounds were tentatively identified as branched alcohols and esters of hexanoic acid. Five commercially available hexanoate esters and two commercially available branched alcohols were identified as new active antifeedants. Both stimulatory and inhibiting compounds were found in the same extracts and co-eluted in the same or adjacent fractions. The mix of semiochemicals of opposite activity in each extract or fraction could explain the stimulatory-, inhibitory-, or sometimes neutral activity. Generally, such co-occurrence confounds the isolation of antifeedants.},
	keywords = {Hylobius abietis},
	isbn = {0098-0331},
	author = {Eriksson, Carina and Mansson, Per E. and Sjodin, Kristina and Schlyter, Fredrik}
}
@article {9920,
	title = {Catching Ips duplicatus (Sahlberg) (Coleoptera: Scolytidae) with pheromone-baited traps: optimal trap type, colour, height and distance to infestation},
	journal = {Pest Management Science},
	volume = {66},
	number = {2},
	year = {2010},
	month = {Feb},
	pages = {213-219},
	abstract = {BACKGROUND: Field trapping experiments were carried out to evaluate effective trap characteristics for maximising Ips duplicatus (Sahlberg) catches in pheromone-baited traps in China. RESULTS: Window-slot and cross-barrier traps had significantly higher catches than multiple-funnel traps. The colour of window-slot traps showed a significant effect on catches, with dark colours (black and red) being more effective than light colours, especially white and yellow. Window-slot traps at a 1.5-2.0 m level caught more beetles than those at either ground level (0-0.5 m) or at 3.5-4.0 m. Ips duplicatus can be attracted to pheromone-baited traps over a distance of >100 m from the forest edge in an open grassy field. There was a strong diurnal pattern of flight activity, with catches on window-slot traps occurring during the daytime with one broad peak at mid- to late afternoon. The seasonal flight activity of I. duplicatus as monitored by pheromone-baited window-slot traps during 2007-2008 indicated that three major flight peaks occurred in early June, late June-early July and late July respectively, suggesting the existence of a potential second generation. CONCLUSION: The optimal trap characteristics will improve the performance of pheromone-baited traps as a critical monitoring or mass-trapping tool to combat outbreaks of this pest species. (C) 2009 Society of Chemical Industry},
	isbn = {1526-498X},
	author = {Chen, Guofa and Zhang, Qing-He and Wang, Yanjun and Liu, Guang-Tian and Zhou, Xiaoming and Niu, Jingfu and Schlyter, Fredrik}
}
@article {9019,
	title = {What Reaches the Antenna? How to Calibrate Odor Flux and Ligand-Receptor Affinities},
	journal = {Chemical Senses},
	volume = {37},
	number = {5},
	year = {2012},
	month = {Jun},
	pages = {403-420},
	abstract = {Physiological studies on olfaction frequently ignore the airborne quantities of stimuli reaching the sensory organ. We used a gas chromatography-calibrated photoionization detector to estimate quantities released from standard Pasteur pipette stimulus cartridges during repeated puffing of 27 compounds and verified how lack of quantification could obscure olfactory sensory neuron (OSN) affinities. Chemical structure of the stimulus, solvent, dose, storage condition, puff interval, and puff number all influenced airborne quantities. A model including boiling point and lipophilicity, but excluding vapor pressure, predicted airborne quantities from stimuli in paraffin oil on filter paper. We recorded OSN responses of Drosophila melanogaster, Ips typographus, and Culex quinquefasciatus, to known quantities of airborne stimuli. These demonstrate that inferred OSN tuning width, ligand affinity, and classification can be confounded and require stimulus quantification. Additionally, proper dose-response analysis shows that Drosophila AB3A OSNs are not promiscuous, but highly specific for ethyl hexanoate, with other earlier proposed ligands 10- to 10 000-fold less potent. Finally, we reanalyzed published Drosophila OSN data (DoOR) and demonstrate substantial shifts in affinities after compensation for quantity and puff number. We conclude that consistent experimental protocols are necessary for correct OSN classification and present some simple rules that make calibration, even retroactively, readily possible.},
	isbn = {0379-864X},
	author = {Andersson, Martin N. and Schlyter, Fredrik and Hill, Sharon Rose and Dekker, Teun}
}
@article {9018,
	title = {Specificity and redundancy in the olfactory system of the bark beetle Ips typographus: single-cell responses to ecologically relevant odors},
	journal = {Journal of Insect Physiology},
	volume = {55},
	number = {6},
	year = {2009},
	month = {June},
	pages = {556-567},
	abstract = {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: [alpha]-pinene, myrcene, p-cymene, myrcene and p-cymene, 1,8-cineole, or [DELTA]3-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. [copyright] 2009 Elsevier Ltd. All rights reserved.},
	isbn = {0022-1910},
	author = {Andersson, Martin N. and Larsson, Mattias C. and Schlyter, Fredrik}
}
@article {9016,
	title = {Attraction Modulated by Spacing of Pheromone Components and Anti-attractants in a Bark Beetle and a Moth},
	journal = {Journal of Chemical Ecology},
	volume = {37},
	number = {8},
	year = {2011},
	month = {Aug},
	pages = {899-911},
	abstract = {Orientation for insects in olfactory landscapes with high semiochemical diversity may be a challenging task. The partitioning of odor plumes into filaments that are interspersed with pockets of {\textquoteright}clean air{\textquoteright} may help filament discrimination and upwind flight to attractive sources in the face of inhibitory signals. We studied the effect of distance between odor sources on trap catches of the beetle, Ips typographus, and the moth, Spodoptera littoralis. Insects were tested both to spatially separated pheromone components (cis-verbenol and 2-methyl-3-buten-2-ol for Ips; (Z,E)-9,11-tetradecadienyl acetate and (Z,E)-9,12-tetradecadienyl acetate for Spodoptera), and to separated pheromone and anti-attractant sources (non-host volatile (NHV) blend for Ips; (Z)-9-tetradecenyl acetate for Spodoptera). Trap catch data were complemented with simulations of plume structure and plume overlap from two separated sources using a photo ionization detector and soap bubble generators. Trap catches of the beetle and the moth were both affected when odor sources in the respective traps were increasingly separated. However, this effect on trap catch occurred at smaller (roughly by an order of magnitude) odor source separation distances for the moth than for the beetle. This may reflect differences between the respective olfactory systems and central processing. For both species, the changes in trap catches in response to separation of pheromone components occurred at similar spacing distances as for separation of pheromone and anti-attractant sources. Overlap between two simulated plumes depended on distance between the two sources. In addition, the number of detected filaments and their concentration decreased with downwind distance. This implies that the response to separated odor sources in the two species might take place under different olfactory conditions. Deploying multiple sources of anti-attractant around a pheromone trap indicated long-distance (meter scale) effects of NHV on the beetle and a potential use for NHV in forest protection.},
	isbn = {0098-0331},
	author = {Andersson, Martin N. and Binyameen, Muhammad and Sadek, Medhat M. and Schlyter, Fredrik}
}
@article {9017,
	title = {Peripheral modulation of pheromone response by inhibitory host compound in a beetle},
	journal = {Journal of Experimental Biology},
	volume = {213},
	number = {19},
	year = {2010},
	month = {Oct 1},
	pages = {3332-3339},
	abstract = {We identified several compounds, by gas chromatographic-electroantennographic detection (GC-EAD), that were antennally active in the bark beetle Ips typographus and also abundant in beetle-attacked spruce trees. One of them, 1,8-cineole (Ci), strongly inhibited the attraction to pheromone in the field. Single-sensillum recordings (SSRs) previously showed olfactory receptor neurons (ORNs) on I. typographus antennae selectively responding to Ci. All Ci neurons were found within sensilla co-inhabited by a pheromone neuron responding to cis-verbenol (cV); however, in other sensilla, the cV neuron was paired with a neuron not responding to any test odorant. We hypothesized that the colocalization of ORNs had a functional and ecological relevance. We show by SSR that Ci inhibited spontaneous activity of the cV neuron only in sensilla in which the Ci neuron was also present. Using mixtures of cV and Ci, we further show that responses to low doses (1-10 ng) of cV were significantly reduced when the colocalized Ci neuron simultaneously responded to high doses (1-10 [mu]g) of Ci. This indicated that the response of the Ci neuron, rather than ligand-receptor interactions in the cV neuron, caused the inhibition. Moreover, cV neurons paired with Ci neurons were more sensitive to cV alone than the ones paired with the non-responding ORN. Our observations question the traditional view that ORNs within a sensillum function as independent units. The colocalization of ORNs might sharpen adaptive responses to blends of semiochemicals with different ecological significance in the olfactory landscape.},
	isbn = {0022-0949},
	author = {Andersson, Martin N. and Larsson, Mattias C. and Blazenec, Miroslav and Jakus, Rastislav and Zhang, Qing-He and Schlyter, Fredrik}
}
@article {9006,
	title = {Pheromone of the elm bark beetle Scolytus laevis (Coleoptera: Scolytidae): stereoisomers of 4-methyl-3-heptanol reduce interspecific competition},
	journal = {Chemoecology},
	volume = {20},
	number = {3},
	year = {2010},
	month = {Sep},
	pages = {179-187},
	abstract = {Stereoisomers of 4-methyl-3-heptanol (MH) are pheromone components of several Scolytus bark beetles. The elm bark beetle Scolytus laevis (Coleoptera: Scolytidae) has in previous studies been caught in traps baited with commercial MH containing all four stereoisomers, but the lure has been considered a weak attractant. In this study, we addressed the question whether stereospecific responses by S. laevis to stereoisomers of MH might contribute to its niche separation from other sympatric Scolytus species. Using GC-MS, we analyzed extracts of hindguts and abdomens from male and female S. laevis and the sympatric S. triarmatus. We also tested all four MH-stereoisomers individually and in combinations in the field to determine their role for S. laevis. All four stereoisomers were synthesized via a boronic ester method with 1,2-dicyclohexylethanediol as chiral director. In addition, the (3S,4R)-stereoisomer of MH was prepared through enantioselective, lipase-mediated transesterification of a mixture of the four stereoisomers of MH. Females of both species contained small amounts of syn-MH, and males contained trace amounts of anti-MH. The anti stereoisomer (3R,4S)-MH was attractive to male and female S. laevis, whereas the syn stereoisomer (3S,4S)-MH acted as an inhibitor or deterrent and reduced the catch when added to the attractive isomer. The syn isomer is the main aggregation pheromone component of the larger and sympatric S. scolytus and possibly also of S. triarmatus. The avoidance response of S. laevis to the (3S,4S)-stereoisomer may reduce interspecific competition for host trees.},
	isbn = {0937-7409},
	author = {Anderbrant, Olle and Matteson, Donald S. and Unelius, C. Rikard and Pharazyn, Philip S. and Santangelo, Ellen M. and Schlyter, Fredrik and Birgersson, Goran}
}
@article {6017,
	title = {Electrophysiological and behavioral responses of Ips subelongatus to semiochemicals from its hosts, non-hosts, and conspecifics in China},
	journal = {Journal of Chemical Ecology},
	volume = {33},
	number = {2},
	year = {2007},
	month = {February},
	pages = {391-404},
	abstract = {Volatiles from hosts, non-hosts, interspecifics, and conspecifics of the Asian larch bark beetle, Ips subelongatus Motsch., were analyzed using both gas chromatographic-electroantennographic detection (GC-EAD) and gas chromatography/mass spectrometry (GC-MS) techniques, and field trapping bioassays in Inner Mongolia, China. GC-EAD experiments indicated that I. subelongatus antennae (both sexes) strongly responded not only to the major male-produced conspecific components, ipsenol, and ipsdienol, but also to other bark beetle compounds (cis-verbenol and verbenone), host monoterpenes (a-pinene, [beta]-pinene, and para-cymene) from Larix sp. logs, and non-host leaf (green leaf volatiles and geranyl acetone) and bark (C8-alcohols and trans-conophthorin) volatiles. Repeatable EAD responses were also found to two compounds from hindgut extracts that are undetectable by GC. One of these minor compounds was identified as amitinol. Field trapping experiments showed that the EAD-active, major male-hindgut component, racemic ipsenol, is the only individual compound that significantly attracted both sexes of I. subelongatus, whereas all other compounds, including previously reported pheromone components of European Ips cembrae, ipsdienol and 3-methyl-3-buten-1-ol, were unattractive. Ipsdienol, 3-methyl-3-buten-1-ol, or their binary blend had no synergistic or antagonistic effects on I. subelongatus attraction when combined with ipsenol, whereas cis-verbenol (a synomone) and verbenone (the antiaggregation semiochemical) inhibited its attraction to the ipsenol-containing attractive blend. A mixture of three EAD-active host monoterpenes, a-pinene, [beta]-pinene, and para-cymene, was unattractive, but interrupted the pheromone response of I. subelongatus. Geranyl acetone, one of the strong EAD-active non-host volatiles also significantly reduced the number of I. subelongatus captured in traps baited with ipsenol-containing attractive blend. Our results add support to the recent phylogenetic finding that European and Asian larch bark beetles should be regarded as two distinct species: I. cembrae infecting larch in Europe and I. subelongatus infesting larch in Asia},
	keywords = {Ips subelongatus},
	isbn = {0098-0331},
	author = {Zhang, Qing-He and Schlyter, Fredrik and Chen, Guofa and Wang, Yanjun}
}
@article {6015,
	title = {Electrophysiological and behavioral responses of Ips duplicatus aggregation pheromone in Inner Mongolia, China: amitinol as a potential pheromone component},
	journal = {Journal of Chemical Ecology},
	volume = {33},
	number = {7},
	year = {2007},
	month = {July},
	pages = {1303-1315},
	abstract = {Volatiles from Ips duplicatus male hindgut extracts and aeration samples of spruce logs colonized by the virgin males were analyzed by coupled gas chromatography-mass spectrometry (GC-MS), coupled gas chromatography-electroantennographic detection (GC-EAD), and field trapping bioassays in Inner Mongolia, China. GC-MS analyses showed that males from nuptial chambers (for reproduction) produced hindgut volatile profiles similar to those of maturation feeding males from the nonreproductive galleries. The known aggregation pheromone components, ipsdienol (Id) and E-myrcenol (EM) are the major constituents of this blend, followed by several minor bark beetle-related compounds: 2-methyl-3-buten-2-ol, ipsenol, cis-verbenol, verbenone, 2-phenylethanol, myrtenol, and trans-myrtanol. The enantiomeric composition of the Id from the male hindgut extracts was determined to be a racemic mixture (50/50) by enantioselective GC. GC-EAD experiments indicated that I. duplicatus antennae from both sexes responded strongly not only to the known aggregation pheromone components, Id and EM, but also to the other minor conspecific-produced compounds. The strongest antennal response was elicited by the major pheromone component, Id, which was ca. 2-3 times higher than that elicited by the second component, EM. Electroantennogram dose-responses indicated that antennal response threshold to Id was approximately 100 times lower than that of EM. No synergistic effects between these occurred at peripheral level. A strong and repeatable EAD response was found to a trace compound (flame ionization detection undetectable) from both hindgut and aeration samples. The compound was identified as amitinol (At) based on the retention time and a further EAD analysis of a synthetic mixture. In the field trapping experiments, At increased the attraction of I. duplicatus to the traps baited with a binary blend of EM/Id (1:1) in a synergistic manner when tested at a low release rate (1:1:0.1) but had no effect on catches at the high release rate (1:1:1). This result suggests that At might be a part of the Chinese I. duplicatus aggregation pheromone system. The production ratios of EM/Id from the Inner Mongolian population (EM/Id[approximately equal]1:2.0-4) were twice as high as those reported from Europe (EM/Id[approximately equal]1:9), corresponding well with the differences in the optimal response ratios},
	keywords = {Ips duplicatus},
	isbn = {0098-0331},
	author = {Zhang, Qing-He and Schlyter, Fredrik and Liu, Guang-Tian and Sheng, Mao-Ling and Birgersson, Goran}
}
