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See detailAre bogs reservoirs for emerging disease vectors? Evaluation of Culicoides populations in the Hautes Fagnes Nature Reserve (Belgium)
Zimmer, Jean-Yves ULg; Losson, Bertrand ULg; Smeets, François ULg et al

Poster (2013, October)

Several species of Culicoides (Diptera: Ceratopogonidae) biting midges serve as biological vec{ors for the bluetongue virus (BTV) and the recently described Schmallenberg virus in northern Europe. since ... [more ▼]

Several species of Culicoides (Diptera: Ceratopogonidae) biting midges serve as biological vec{ors for the bluetongue virus (BTV) and the recently described Schmallenberg virus in northern Europe. since their recent emergence in this part of the continent, these diseases have caused considerable economic losses to the sheep and cattle industries. Much data is nou, âvailable that describe the distribuüon, population dynamics, and feeding habits of these insects. However, little is known regarding the presence of culicoides in unusual habitats such as peaÿ marshes, nor their potential vector capacity. This study evaluated Culicoides biting midges present in the bogs of a Belgian nature reserve compared to those residing at a nearby cattle farm. Culicoides were trapped in 2011 at four different sites (broadleaved and coniferous forested areas, open environments, and at a scientific station) located in the Hautes Fagnes Nature Reserve (Belgium). An additional light trap was operated on a nearby caftle farm. High numbers of biting midges were captured in the marshy area and most of them were Culicoides impunc{atus, a potential vector of BïV and other pâthogens. ln addition, fewer numbers of c. obsoletus/c. scoticus species, C. chiopterus, and C. dewulfi were observed in the bogs compared to the farm. The wet environment and oligotrophic nature of the soil were probably responsible for these changes in the respective populations. A total of 297,808 Culicoides midges belonging to 27 species were identified during this study and 3 of these species (C. sphagnumensis, C. clintoni and C. comosioculatus) were described in Belgium for the first time. [less ▲]

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See detailFirst Evidence of a Volatile Sex Pheromone in Harmonia axyridis (Pallas)
Fassotte, Bérénice ULg; Fischer, Christophe ULg; Durieux, Delphine ULg et al

Poster (2013, October)

Until now, no volatile sex pheromone has been highlighted in Coccinellidae but various studies have suggested the existence of such molecules. In the present work, we have sampled volatile organic ... [more ▼]

Until now, no volatile sex pheromone has been highlighted in Coccinellidae but various studies have suggested the existence of such molecules. In the present work, we have sampled volatile organic compounds released in the headspace of virgin females in the multicolored Asian ladybeetle, Harmonia axyridis (Pallas), that were either allowed or not to feed on pea aphids (Acyrthosiphon pisum Harris). When fed on aphids, virgin females showed a stereotypical “calling behavior”, commonly associated with the emission of a sex pheromone in several Coleoptera species. Behavioral assays conducted with calling females in a four-arm olfactometer demonstrated that the blend of released volatile compounds was attractive at a distance for males, but not for other females. The headspace of virgin females that were not previously fed with aphids was not attractive for either sex. GC-MS analyses revealed the presence of five compounds in the volatile blend: (–)-β-caryophyllene, β-elemene, methyl-eugenol, α-humulene and α-bulnesene. Subsequently, we have collected and quantified the constituents from the blend over a period of 9 days after exposure to aphids. All five compounds were produced exclusively after feeding virgin females with aphids, and their quantity significantly increased during the whole period of collection. (–)-β-caryophyllene was found to be the major constituent, representing between 80 and 86 % of the total blend. All these results could promote the development of more specific and efficient management methods to manipulate the movements of this invasive ladybeetle and to reduce its negative impacts on biodiversity. [less ▲]

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See detailCrop association to improve biological control: case study on pea and wheat aphids
Chevalier Mendes Lopes, Thomas ULg; Bodson, Bernard ULg; Francis, Frédéric ULg

Conference (2013, September 13)

Nowadays, strategies used to control aphids in fields of pea, Pisum sativum L., and wheat, Triticum aestivum L., still rely on synthetic insecticides which have negative effects on the environment and ... [more ▼]

Nowadays, strategies used to control aphids in fields of pea, Pisum sativum L., and wheat, Triticum aestivum L., still rely on synthetic insecticides which have negative effects on the environment and human health. This research focused on the development of sustainable alternative methods, with special emphasis on cultural practices and plant management systems. Increasing the diversity within crops may have several beneficial effects on pest control, creating attractive habitats for indigenous beneficial fauna and simultaneously deterring pests – the ‘push-pull’approach. In this field study, two wheat/pea associations (mixed cropping and strip cropping) where compared to monocultures of pea and wheat. The abundance and diversity of adult aphidophagous insects (predators and parasitoids) were accessed weekly using yellow traps, while aphids were observed directly on plants. In both crops, the percentage of plants infested with aphids and density of aphid colonies were significantly higher in monocultures during periods of aphid abundance. Mixed cropping was particularly beneficial for the pea, whereas strip-cropping was more efficient for the wheat. The abundance of beneficials was significantly higher in monocultures comparing to the other treatments. Quantitative aphid-natural enemy food webs showed that the abundance of the two main ladybird species, Coccinella septempunctata L. and Propylea quatuordecimpunctata (L.), increased with the occurrence of Acyrthosiphon pisum (Harris) on pea plants. Abundance of the two main species of Syrphidae, Sphaerophoria scripta (L.) and Eupeodes corollae (F.), increased with the occurrence of Sitobion avenae (F.) and Metopolophium dirhodum (Walker) on wheat plants. This study shows that increasing diversity within crops can help lower aphid infestations. However, additional methods are needed to more efficiently attract aphidophagous beneficials and promote the natural control of aphids. [less ▲]

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See detailThe Multicoloured Asian Ladybird, invasive or not in agroecosystems ?
Vandereycken, Axel ULg; Durieux, Delphine ULg; Fassotte, Bérénice ULg et al

Poster (2013, September 10)

The Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is known to thrive principally in shrubby and arboreal habitats. Its occurrence in agroecosystems remains poorly ... [more ▼]

The Multicoloured Asian Ladybird, Harmonia axyridis Pallas (Coleoptera: Coccinellidae) is known to thrive principally in shrubby and arboreal habitats. Its occurrence in agroecosystems remains poorly documented. This study focuses on the occurrence of this exotic species and its seasonal abundance in various field crops. The abundance of adults and larvae of H. axyridis was evaluated over a four-year period, from 2009 to 2012, in four important agronomical crops (wheat, corn, broad bean and potato) in Belgium. A total of 28 aphid predator species were observed including 14 coccinellid species, 13 hoverfly species and one lacewing species. H. axyridis is present and reproduces in all of the four crops studied, with the largest numbers recorded in corn and broad bean crops. In corn, H. axyridis numbers were found to increase over the four inventoried year, reaching 86% of the aphid predators in 2012, while it represented only 15% in 2009. H. axyridis was not always recorded where aphids were abundant, e.g. aphids were abundant on wheat where no H. axyridis were recorded. H. axyridis starts reproducing after the peak in aphid population, suggesting that H. axyridis is able to complete its development by feeding on alternative prey such as larvae and pupae of the same and other species of ladybird and other aphidophagous species. H. axyridis is often considered to be bivoltine but it only completes one generation per year in field crops. The second generation generally develops late in the season in other habitats. Harmonia axyridis is an invasive and an intraguild predator present in high quantities in some specific crops. In these crops, H. axyridis could negatively impact on population of native species due to IGP observed in several other studies. [less ▲]

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See detailProteomic Investigation of Aphid Honeydew Reveals an Unexpected Diversity of Proteins
Sabri, Ahmed; Vandermoten, Sophie ULg; Leroy, Pascal et al

in PLoS ONE (2013), 8(9),

Aphids feed on the phloem sap of plants, and are the most common honeydew-producing insects. While aphid honeydew is primarily considered to comprise sugars and amino acids, its protein diversity has yet ... [more ▼]

Aphids feed on the phloem sap of plants, and are the most common honeydew-producing insects. While aphid honeydew is primarily considered to comprise sugars and amino acids, its protein diversity has yet to be documented. Here, we report on the investigation of the honeydew proteome from the pea aphid Acyrthosiphon pisum. Using a two-Dimensional <br />Differential in-Gel Electrophoresis (2D-Dige) approach, more than 140 spots were isolated, demonstrating that aphid honeydew also represents a diverse source of proteins. About 66% of the isolated spots were identified through mass spectrometry analysis, revealing that the protein diversity of aphid honeydew originates from several organisms (i.e. the host aphid and its microbiota, including endosymbiotic bacteria and gut flora). Interestingly, our experiments also allowed to identify some proteins like chaperonin, GroEL and Dnak chaperones, elongation factor Tu (EF-Tu), and flagellin that might act as mediators in the plant-aphid interaction. In addition to providing the first aphid honeydew proteome analysis, we propose to reconsider the importance of this substance, mainly acknowledged to be a waste product, from the aphid <br />ecology perspective. [less ▲]

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See detailInteractions of two aphid species on the african eggplant, sorrel and amaranth
Bayendi-Loudit, Sandrine ULg; Chevalier Mendes Lopes, Thomas ULg; Francis, Frédéric ULg

Poster (2013, September)

Aphids (Homoptera: Aphididae) are polyphagous insects which can be found on several crops in temperate zones, as well as in the tropics. The multiplication of Aphis gossypii Glover (C9 cucumber, Burk ... [more ▼]

Aphids (Homoptera: Aphididae) are polyphagous insects which can be found on several crops in temperate zones, as well as in the tropics. The multiplication of Aphis gossypii Glover (C9 cucumber, Burk cotton and Pipo pepper strains) and Myzus persicae Sulzer was studied in the laboratory on three plant species: African eggplant, Solanum aethiopicum, sorrel, Hibiscus sabdariffa, and amaranth, Amaranthus spp. Periodic counts were carried out to monitor population growth. The multiplication rate of M. persicae wass higher than that of A. gossypii when these two species were present together on eggplant. Amaranth was less suitable for the development of both species, but Myzus persicae again had a better multiplication rate than Aphis gossypii. This study illustrated the importance of considering not only one pest species, but the whole herbivore guild, especially when biological control is important. [less ▲]

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See detailIsolation and Cultivation of a Xylanolytic Bacillus subtilis Extracted from the Gut of the Termite Reticulitermes santonensis
Tarayre, Cédric ULg; Brognaux, Alison ULg; Brasseur, Catherine ULg et al

in Applied Biochemistry and Biotechnology (2013)

The aim of this work was the isolation of xylanolytic microorganisms from the digestive tract of the termite Reticulitermes santonensis. The reducing sugars released after the hydrolysis of xylans can be ... [more ▼]

The aim of this work was the isolation of xylanolytic microorganisms from the digestive tract of the termite Reticulitermes santonensis. The reducing sugars released after the hydrolysis of xylans can be further fermented to provide bioethanol. A xylanolytic strain of Bacillus subtilis was isolated from the hindgut of the termite and displayed amylase and xylanase activities. The bacterium was grown on media containing agricultural residues: wheat bran, wheat distiller’s grains, and rapeseed oil cake. Wheat bran led to the highest induction of xylanase activity, although the development of the strain was less fast than in the other media. It was possible to reach maximal xylanase activities of 44.3, 33.5, and 29.1 I.U./ml in the media containing wheat bran, wheat distiller’s grains, and rapeseed oil cake, respectively. Mass spectrometry identified a wide range of xylose oligomers, highlighting an endoxylanase activity. The enzyme was stable up to 45 °C and displayed an optimal pH close to 8. [less ▲]

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See detailAre Bogs Reservoirs for Emerging Disease Vectors? Evaluation of Culicoides Populations in the Hautes Fagnes Nature Reserve (Belgium)
Zimmer, Jean-Yves ULg; Smeets, François ULg; Simonon, Grégory et al

in PLoS ONE (2013), 8(6),

Several species of Culicoides (Diptera: Ceratopogonidae) biting midges serve as biological vectors for the bluetongue virus (BTV) and the recently described Schmallenberg virus (SBV) in northern Europe ... [more ▼]

Several species of Culicoides (Diptera: Ceratopogonidae) biting midges serve as biological vectors for the bluetongue virus (BTV) and the recently described Schmallenberg virus (SBV) in northern Europe. Since their recent emergence in this part of the continent, these diseases have caused considerable economic losses to the sheep and cattle industries. Much data is now available that describe the distribution, population dynamics, and feeding habits of these insects. However, little is known regarding the presence of Culicoides in unusual habitats such as peaty marshes, nor their potential vector capacity. This study evaluated Culicoides biting midges present in the bogs of a Belgian nature reserve compared to those residing at a nearby cattle farm. Culicoides were trapped in 2011 at four different sites (broadleaved and coniferous forested areas, open environments, and at a scientific station) located in the Hautes Fagnes Nature Reserve (Belgium). An additional light trap was operated on a nearby cattle farm. Very high numbers of biting midges were captured in the marshy area and most of them (70 to 95%) were Culicoides impunctatus, a potential vector of BTV and other pathogens. In addition, fewer numbers of C. obsoletus/C. scoticus species, C. chiopterus, and C. dewulfi were observed in the bogs compared to the farm. The wet environment and oligotrophic nature of the soil were probably responsible for these changes in the respective populations. A total of 297,808 Culicoides midges belonging to 27 species were identified during this study and 3 of these species (C. sphagnumensis, C. clintoni and C. comosioculatus) were described in Belgium for the first time. [less ▲]

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See detailOccurrence of aphid predator species in both organic and conventional corn and broad bean
Vandereycken, Axel ULg; Joie, Emilie ULg; Francis, Frédéric ULg et al

in Entomologie Faunistique = Faunistic Entomology (2013), 66

Organic farming has been suggested to enhance beneficial species abundance and diversity in agrosystem habitats. In this study, the abundance of aphid predators was compared in organic and conventional ... [more ▼]

Organic farming has been suggested to enhance beneficial species abundance and diversity in agrosystem habitats. In this study, the abundance of aphid predators was compared in organic and conventional corn and broad bean fields during a two-year inventory. In both farming strategies, there were no differences between species diversity. Five aphid predator species were mainly observed: Coccinella septempunctata L. 1758 (Coleoptera: Coccinellidae), Propylea quatuordecimpunctata (L. 1758) (Coleoptera: Coccinellidae), Harmonia axyridis Pallas 1773 (Coleoptera: Coccinellidae), Chrysoperla carnea (Stephens 1836) (Neuroptera: Chrysopidae) and Episyrphus balteatus (De Geer 1776) (Diptera: Syrphidae). Differences in abundance of aphidophagous species between conventional and organic crop fields were observed even if not always in favour of the latter condition. The abundance of the five above- mentioned aphidophagous species varied for the most part according to almost all the observed parameters, including sampled year, crop and agricultural practices. In conclusion, our findings do not support organic practices in corn and broad bean as key options to increase the biodiversity and abundance of aphid natural enemies. [less ▲]

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See detailEmission of sulfur-containing volatiles from Arabidopsis thaliana (L.) Heynh Col-0 related to diamondback moth (Plutella xylostella (L.)) infestation
Hien, Truong Thi Dieu ULg; Delaplace, Pierre ULg; Francis, Frédéric ULg et al

Poster (2013, June 10)

Herbivore-infested plants often release a variety of volatile organic compounds (VOCs). Here, we studied the effects of feeding Plutella xylostella (L.) (0, 3, 9, 20 pest larvae within 0-4 h and 4-8 h ... [more ▼]

Herbivore-infested plants often release a variety of volatile organic compounds (VOCs). Here, we studied the effects of feeding Plutella xylostella (L.) (0, 3, 9, 20 pest larvae within 0-4 h and 4-8 h infestation, respectively) on the emission of sulfur-containing VOCs in Arabidopsis thaliana (L.) Heynh Col-0 (A.t. Col-0) by headspace solid-phase micro-extraction coupled to gas chromatography - mass spectrometry (HS-SPME-GC/MS). The analytical results showed that the relative emission of sulfur-containing metabolites increased significantly in Arabidopsis plants subjected to P. xylostella infestation according to the density and residence duration of pest larvae on shoot organs. The main compound from infested plants was dimethyl disulfide. We suggest that the correlations between the stress level (density and time infestation) and the sulfides observed in this study provide a means to understand the changes of VOCs profile of plant under chewer infestation. [less ▲]

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See detailIsolation and cultivation of cellulolytic and xylanolytic bacteria and molds extracted from the gut of the termite Reticulitermes santonensis (3DV.1.14)
Tarayre, Cédric ULg; Bauwens, Julien ULg; Mattéotti, Christel et al

Poster (2013, June)

Biofuel production can be based on the use of agro-residues, consisting in a complex lignocellulosic structure which is not easily hydrolysable. The digestive tract of the termite Reticulitermes ... [more ▼]

Biofuel production can be based on the use of agro-residues, consisting in a complex lignocellulosic structure which is not easily hydrolysable. The digestive tract of the termite Reticulitermes santonensis contains a diversified microflora able to hydrolyze the wood components. Bacteria, molds and protists form efficient consortia, able to break the lignocellulosic complex by producing enzymes, such as xylanases and cellulases. Our purpose is the isolation of microbial strains from termite guts in order to evaluate their potential for hydrolysis of lignocellulosic materials. Termites were fed using different diets chosen to improve the xylanolytic and cellulolytic microflora: wood, microcristalline cellulose (added with lignin or not), α-cellulose (added with lignin or not) and birchwood xylan. Then, dissections were realized to isolate the potential xylanolytic and cellulolytic strains. This approach led us to isolate and to study several strains of bacteria (Bacillus sp. strain CTGx and Chryseobacterium sp. strain CTGx) and molds (Trichoderma virens strain CTGx and Sarocladium kiliense strain CTGx). These microorganisms were able to hydrolyze starch, xylan, cellulose, carboxymethylcellulose, esculin, β-glucan and Whatman® filter paper. They can produce glucose and xylose monomers and oligomers which can be further fermented to produce bioethanol. [less ▲]

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See detailResearch of New Enzyme Producing Strains in the Gut of the Termite Reticulitermes santonensis
Tarayre, Cédric ULg; Bauwens, Julien ULg; Mattéotti, Christel et al

Poster (2013, June)

Termites contain a complex microflora inside of their guts. Inferior termites contain bacteria, mycetes and protists that interact to degrade vegetable components. These strains act as consortia to break ... [more ▼]

Termites contain a complex microflora inside of their guts. Inferior termites contain bacteria, mycetes and protists that interact to degrade vegetable components. These strains act as consortia to break natural materials by secreting various enzymes. Our aim was the isolation and cultivation of microorganisms in order to produce new enzymes that can be further used in green chemistry. Termites were fed with different diets: pinewood, microcristalline cellulose (added with lignin or not), α-cellulose (added with lignin or not) and birchwood xylan. Then, dissections were realized to isolate interesting strains. All the microorganisms were subjected to enzyme assays. That technique allowed us to isolate and to cultivate various strains of bacteria, molds and protists. Three strains of bacteria, two strains of molds and one strain of protist were isolated and displayed different enzymatic activities. The bacteria Bacillus subtilis strain ABGx, Bacillus sp. strain CTGx and Chryseobacterium sp. strain CTGx displayed amylase, cellulase and xylanase activities. The molds Trichoderma virens strain CTGx and Sarocladium kiliense strain CTGx were also able to produce those enzymes. However, the protist Poterioochromonas sp. was found to produce only amylase. In conlusion, the termite gut is a complex culivation medium that provides a habitat for many microorganisms that show interesting enzymatic activities. [less ▲]

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