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See detailEffective concentrations of garlic distillate (Allium sativum) for the control of Tetranychus urticae (Tetranychidae)
Attia, Sabrine; Grissa, Kaouthar Lebdi; Mailleux, Anne-Catherine et al

in Journal of Applied Entomology (2011)

The two-spotted spider mite, Tetranychus urticae Koch, is a worldwide pest that feeds on a large variety of plant families. Because its resistance to acaricides is spreading rapidly, the development of ... [more ▼]

The two-spotted spider mite, Tetranychus urticae Koch, is a worldwide pest that feeds on a large variety of plant families. Because its resistance to acaricides is spreading rapidly, the development of new biological control tactics for population management is crucial. Plant extracts, such as garlic extract (Allium sativum Linn.), may represent viable alternatives, because they are currently considered to be minimum-risk pesticides. Although garlic is known for its acaricidal properties, the extract concentration that provides the most efficient control has not yet been precisely determined. In this study, we conducted a series of laboratory experiments to determine the susceptibility of adult females to different concentrations of garlic extract. Fresh garlic cloves were steam-distilled and sprayed using a Potter spray tower. Mortality and fecundity were measured upon treatment with garlic extract concentrations ranging from 0.46 to 14.4 mg/l. Female mortality increased with concentration, with LD50 and LD90 values of 7.49 and 13.5 mg/l, respectively. Reduced fecundity was previously observed at concentrations of 0.36 and 0.74 mg/l. The chemical composition of the Allium sativum distillate was characterized by reversed-phase high-performance liquid chromatography coupled with photodiode array detection, GC/MS and Fast GC-FID against an authentic standard (Standard, Bioextract).Vinyl dithiin, diallyl disulphide, diallyl trisulphide and methyl allyl trisulphide were identified based on their mass spectra. Sesquiterpenoids were identified by their retention index. [less ▲]

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See detailGeographic and genetic variation of olfactory communication in butterflies: the male sex pheromone of Bicyclus butterfly species
Bacquet, Paul; Brattström, O.; Wang, H. L. et al

in Abstract book (2010, December 17)

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See detailEtude chromatographique de substances volatiles : cas des sémiochimiques
Heuskin, Stéphanie ULg

Scientific conference (2010, November)

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See detailComparative toxicity of Deverra scoparia essential oil and blends of its major constituents against Tetranychus urticae Koch
Attia, Sabrine; Grissa, Kaouthar Lebdi; Lognay, Georges ULg et al

Poster (2010, October 14)

The phytophagous two-spotted spider mite Tetranychus urticae Koch is a ubiquitous species, present worlwide on a large variety of plant families. Since T. urticae resistance spread rapidly, biological ... [more ▼]

The phytophagous two-spotted spider mite Tetranychus urticae Koch is a ubiquitous species, present worlwide on a large variety of plant families. Since T. urticae resistance spread rapidly, biological control tactics are crucial to manage spider mite populations. In this respect, plant-derived essential oil products are a good alternative as they are, in general, considered as minimum-risk pesticides. In that context, laboratory experiments were conducted to assess the toxicity of essential oil of Deverra scoparia endemic plant to North Africa on females of the two spotted spider mite T. urticae (Koch). Essential oil was distillated from fresh leaves from D. scoparia and was sprayed on groups of adults females. The susceptibility of these females to D. scoparia essential oil was tested. A series of dilutions were used to bracket the dose-response range. Tests proved that female mortality increased with essential oil concentration with DL50 and DL90 values of 1.79 mg/l and 3.16 mg/l, respectively. The analysis of D. scoparia essential oil using GC-MS revealed presence of 10 major constituents: alpha-thujene, alpha-pinene, sabinene, myrcene, 3-carene, ocimene, terpinene-4-ol, pulegone, eugenol and beta-eudesmol. For a comprehensive evaluation of the potential of D. scoparia essential oil as acaricidal, individual blends activity of these constituents were tested against T. urticae female. Toxicity of blends of different components indicated significant differences among the active and inactive components, with the presence of all constituents necessary to have toxicity near to that of whole D. scoparia oil. The results showed that natural oil of D. scoparia and some of its constituents have potential for development as botanical acaricide, at least against T. urticae. [less ▲]

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See detailDevelopment of biological control formulations incorporating components of plant origin
Heuskin, Stéphanie ULg; Lorge, Stéphanie; Verheggen, François ULg et al

in Journée Scientifique annuelle de la Société Royale de Chimie: Jeudi 14 octobre 2010, Gembloux Agro-Bio Tech, Université de Liège, Chimie verte (2010, October 14)

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been considered within various integrated pest management IPM strategies. Herein, two sesquiterpenoids: E-β ... [more ▼]

Semiochemicals – informative molecules used in insect-insect or plant-insect interactions – have been considered within various integrated pest management IPM strategies. Herein, two sesquiterpenoids: E-β-farnesene and E-β-caryophyllene have been formulated for their potential properties as aphid enemies attractants. Indeed, E-β-farnesene, the alarm pheromone of many aphid species [1], has also been identified as a kairomone by attracting and inducing oviposition of aphid predators (Episyrphus balteatus De Geer (Diptera: Syrphidae)) [2-5] and by attracting aphid parasitoids (Aphidius ervi Haliday (Hymenoptera: Braconidae)) [6, 7]. E-β-caryophyllene was identified as a potential component of the aggregation pheromone of the Asian ladybird, Harmonia axyridis Pallas [8, 9]. The two products have been purified from essential oils of Matricaria chamomilla L. (Asteraceae) and Nepeta cataria L. (Lamiaceae) [10, 11]. Natural and biodegradable slow-release devices have been investigated in order to deliver these molecules. Moreover, due to their sensitivity to oxidation, the sesquiterpenes needed to be protected. For this purpose, alginate (hydrophilic matrix with low oxygen permeability) was used as polymer for the formulations: the main objective was to hold and deliver semiochemical substances in a controlled way. Consequently, a careful selection of alginates was realised for encapsulation. Formulated beads showed different structural and encapsulation properties depending on factors such as polymer concentration, ionic strength, type and concentration of cross-linker ion,... The gel structure influenced diffusion properties. Alginate formulations were characterized by texturometry and by confocal microscopy in order to observe the distribution of semiochemicals in alginate network. The last step consisted in studying release rate of semiochemicals in laboratory-controlled conditions by adapted trapping and Fast-GC procedures [10,11]. [less ▲]

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See detailBiological control formulations incorporating essential oils' components
Heuskin, Stéphanie ULg; Lorge, Stéphanie; Wathelet, Jean-Paul ULg et al

in Lochynski, Stanislaw; Wawrzenczyk, Czeslaw (Eds.) 41th International Symposium on Essential Oils - Programme and Book of Abstracts (2010, September)

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See detailVariabilité et évolution des phéromones du genre de papillons Bicyclus (Nymphalidae, Satyrinae), et implication dans sa diversification.
Bacquet, Paul; Brattström, O.; Brakefield, P. M. et al

in VII Conférence Internationale Francophone d'Entomologie (2010, July)

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See detailPheromone variability and evolution in the butterfly genus Bicyclus, and implication in its diversification
Bacquet, Paul; Brattström, O.; Brakefield, P. M. et al

Poster (2010, May 05)

The evolution of olfactive communication in generating reproductive isolation among species remains poorly understood (Smadja & Butlin 2009). In Lepidoptera, studies have mainly focused on long-distance ... [more ▼]

The evolution of olfactive communication in generating reproductive isolation among species remains poorly understood (Smadja & Butlin 2009). In Lepidoptera, studies have mainly focused on long-distance pheromones produced by moths. Moth sex pheromones have been shown to display inter-population variation (e.g. Tòth et al. 1992, McElfresh & Millar 2008 and ref. within, Groot et al. 2009) and to be involved in interspecific isolation (e.g. Löfstedt et al. 1991, Groot et al. 2006). In butterflies, the few existing studies on sex pheromones have mainly focused on the identification of the male specific compounds and the demonstration of their behavioural activity in courtship (e.g. Grula et al. 1980, Nieberding et al. 2008, Yildizhan et al. 2009), but have failed so far to highlight a role in reproductive isolation (Friberg et al. 2008). In the species-rich Bicyclus genus Kirby, 1871 (Nymphalidae, Satyrinae) the structures producing the pheromones, i.e. the androconia, are key characters to discriminate among species (Condamin 1973). In B. anynana (Butler, 1879), the male sex pheromone (MSP) has been shown to play a role in mate choice (Costanzo & Monteiro 2007, Nieberding et al. 2008), to be heritable, and particular ratios of the pheromone components are under strong sexual selection (Nieberding et al, unpubl. data). Therefore, we expect that pheromone evolution is responsible for reproductive isolation and diversification in this butterfly group. In this framework, our research project aims at understanding the evolution of MSP at the interspecific level across the Bicyclus genus and specifically at testing their potential role in the speciation process. Potential MSP of several species across the Bicyclus genus have been identified by gas chromatography and mass spectrometry. Observed differences in pheromone composition between species are compared in a phylogenetic framework to the molecular tree of the species (following Oliver et al. 2009). We expect the evolutionary rate of MSP to be unlinked to the molecular tree if MSP are under sexual selection across the genus (i.e. saltational evolution following Symonds & Elgar 2004, Shirangi et al. 2009). Moreover, if MSP generated reproductive isolation between species in a “reinforcement” process, we expect higher differences of MSP composition between sympatric species than between allopatric species and an increase of this pattern for younger species compared to older species (Lukhtanov et al. 2006). [less ▲]

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See detailOptimisation of slow-release formulations as biological control devices
Heuskin, Stéphanie ULg; Lorge, Stéphanie; Debatty-Mestdagh, Michelle et al

Poster (2010, May 05)

E-β-Farnesene, the alarm pheromone of many aphid species and β-caryophyllene, recently identified as one of the possible component of the aggregation pheromones of the Asian ladybeetles Harmonia axyridis ... [more ▼]

E-β-Farnesene, the alarm pheromone of many aphid species and β-caryophyllene, recently identified as one of the possible component of the aggregation pheromones of the Asian ladybeetles Harmonia axyridis Pallas, are considered as two sesquiterpenes attractive for aphids’ predators and parasitoids, Epysirphus balteatus De Geer and Aphidius ervi Haliday, respectively. In the present research, alginate gel beads formulations were optimised as semiochemical slow-release devices. The formulations were evaluated in terms of volatiles release capacity, protection efficiency of sesquiterpenes against oxidation, and biological activity towards Epysirphus balteatus and Aphidius ervi. Moreover, the sesquiterpenes used in the formulations were obtained from natural matrices. Indeed, they were purified by flash chromatography fractionation of essential oils of Matricaria chamomilla L. and Nepeta cataria L., for obtaining E-β-farnesene and β-caryophyllene, respectively. The purities of the fractions were determined by means of a fast GC analytical method optimised for a good resolution of terpenes in less than five minutes. The experiments can conclude that the alginate gel beads formulations are efficient as biological control devices considering the results obtained with the various biological tests led on predators and parasitoids. Moreover, the sesquiterpenes are more protected when formulated in alginate beads than without formulation. The devices allow also a slow-release of semiochemicals during a long time (at least 40 days) depending on physico-chemical parameters (temperature, relative humidity). A mathematical modelisation of semiochemicals release is presently in study. [less ▲]

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See detailHarmonia axyridis (Pallas) secondary metabolites quantification in relation with aposematism : Part I : Harmonine quantification
Fischer, Christophe ULg; Heuskin, Stéphanie ULg; Laurent, Pascal ULg et al

Poster (2010, January)

These last few years, the multicoloured Asian ladybird, Harmonia axyridis Pallas (Insects: Coleoptera: Coccinellidae), an invasive species, has swiftly spread out in Europe. This aposematic and highly ... [more ▼]

These last few years, the multicoloured Asian ladybird, Harmonia axyridis Pallas (Insects: Coleoptera: Coccinellidae), an invasive species, has swiftly spread out in Europe. This aposematic and highly polymorphic insect is problematic in several ways. It seems to outcompete native coccinellid species; they can group on fruits in vineyards and spoil wine when crushed with grapes; they can aggregate by hundreds in houses to winter. This study aims to investigate the relations between the chemical defences of H. axyridis and warning signals expressed by this bug. To achieve this goal, two original quantification methods of H. axyridis secondary metabolites have been undertaken. The first one allows Fast-GC quantifying harmonine, its main defence alkaloid. The other one permits to determine its emission rate of 2-isopropyl-3-methoxypyrazine, a highly odorous compound probably involved in the communication between individuals and in the aposematism of this insect. This last point will be detailed in another poster. Firstly, a method of extraction, acetylation and purification of harmonine from H. axyridis has been devised to obtain a calibration standard because this molecule is not commercially available. The identity of the extracted compound has been confirmed by mass spectrometry and multidimensional NMR. The GC purity of this N,N-diacetylharmonine is of 100%. During the experiments, its stability in acetone solution at 4°C has been verified. Using this purified molecule, an original method of harmonine quantification has been developed by fast gas chromatography and validated using accuracy profile. The method has been validated for concentrations ranging from 28µg/ml to more than 264µg/ml, with a maximal error risk of 20%. From about 100µg/ml, peaks symmetry decreased, but did not influence the quantification. That accuracy profile validation has been compared with a more classical validation using AOAC (2006) norm, which confirmed the first validation. This method allows quantifying harmonine in one single insect. Harmonine has been quantified in 80 H. axyridis divided into four groups of at least 15 individuals on basis of the morph type and the elytra hue. Males and females harmonine contents did not significantly differ. The mean harmonine content was of 106.6µg/individual with a standard deviation of 80.2µg/individual. The results distribution obtained was not normal and a strong variability between individuals was observed, which explains the high standard deviation. These results and those of the pyrazine and colour analysis have been statistically analyzed in order to show potential correlations between these factors. It would appear that elytra colour is linked with the insect harmonine content. Individuals with a non-melanic orange colour presented harmonine content significantly higher than other studied colours. The harmonine content does not seem linked to the pyrazine emission rate. [less ▲]

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See detailHarmonia axyridis (Pallas) secondary metabolites quantification in relation with aposematism : Part II : Pyrazine quantification
Fischer, Christophe ULg; Heuskin, Stéphanie ULg; Marlet, Christelle ULg et al

Poster (2010, January)

The main objective of this study is to investigate the presence of links between chemical defences and warning signals presented by Harmonia axyridis (Pallas), the multicoloured Asian ladybird (Insects ... [more ▼]

The main objective of this study is to investigate the presence of links between chemical defences and warning signals presented by Harmonia axyridis (Pallas), the multicoloured Asian ladybird (Insects: Coleoptera: Coccinellidae). This second part describes an original quantification method for 2-isopropyl-3-methoxypyrazine (IPMP) by active sampling on thermally desorbed adsorbent (TD) coupled with GC-MS analysis. This highly odorous compound is supposed to be implicated in intra- and interspecific communication. In order to allow harmonine quantification (a defence alkaloid, see Part 1), this method avoid any hemolymph loses by the ladybird (Coccinellids can emit hemolymph when stressed). This method is non-lethal and applicable on one single insect. The quantification method has been validated from 37,5pg to 10 000 pg per adsorbent cartridge. On this range, there is no breakthrough and desorption is complete (>99.4%). At the LOQ (37.5pg/cartridge), the bias is of 20%, but rapidly decreased to less than 5% on the rest of the validated range (100 to 10 000 pg/cartridge). According to AOAC (2006) norm, this method is repeatable but not reproducible. The IPMP emission rate following a stress has been quantified on 80 H. axyridis grouped in four classes on basis of the morph type and the elytra hue. Males and females emission rates did not significantly differ. The mean emission rate is of 707 pg/4h with an extremely high standard deviation of 1766pg/4h due to a great individual variability and a strongly asymmetric distribution of the results. These results and those of the harmonine and colour analysis have been statistically analyzed in order to show potential correlations between these factors. It seems that elytra colour is linked with the insect IPMP emission rate. Individuals with a melanic red colour presented IPMP emission rate significantly lower than other studied colours. The harmonine content does not seem linked to the pyrazine emission rate. [less ▲]

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See detailA fast gas chromatographic method for the study of semiochemical slow release formulations
Heuskin, Stéphanie ULg; Lorge, Stéphanie; Leroy, Pascal ULg et al

Poster (2010, January)

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See detailValidation of a fast gas chromatographic method for the study of semiochemical slow release formulations
Rozet, Eric ULg; Heuskin, Stéphanie ULg; Lorge, Stéphanie et al

in Journal of Pharmaceutical & Biomedical Analysis (2010), 53

The validation of a fast GC-FID analytical method for the quantitative determination of semiochemical sesquiterpenes (E-β-farnesene and β-caryophyllene) to be used in an integrated pest management ... [more ▼]

The validation of a fast GC-FID analytical method for the quantitative determination of semiochemical sesquiterpenes (E-β-farnesene and β-caryophyllene) to be used in an integrated pest management approach is described. Accuracy profiles using total error as decision criteria for validation were used to verify the overall accuracy of the method results within a well defined range of concentrations and to determine the lowest limit of quantification for each analyte. Furthermore it allowed to select a very simple and reliable regression model for calibration curve for the quantification of both analytes as well as to provide measurement uncertainty without any additional experiments. Finally, this validated method was used for the quantification of semiochemicals in slow release formulations. The goal was to verify the protection efficiency of alginate gel beads formulations against oxidation and degradation of sesquiterpenes. The results showed that the alginate beads are adequate slow release devices which protect the bio-active molecules during at least twenty days. [less ▲]

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See detailEtude chromatographique de substances volatiles: cas des sémiochimiques
Heuskin, Stéphanie ULg

Scientific conference (2009, November 10)

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See detailEtude chromatographique de substances volatiles : cas des sémiochimiques
Heuskin, Stéphanie ULg

Scientific conference (2009, November)

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See detailValidation de méthodes analytiques: le profil d'exactitude
Heuskin, Stéphanie ULg

Scientific conference (2009, October 28)

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