Isolation of Serratia marcescens involved in chitin degradation in the bulb mite Rhizoglyphus robini

There is an increasing awareness of the importance of the microbiome of arthropods to understand their host’s biology. In the bulb mite, Rhizoglyphus robini, associated bacteria have been found to be involved in its chitinolytic abilities. The bulb mite, a plant pest feeding on below- ground parts of mostly Liliaceae crops, prefers fungus- infested plants. Moreover its fitness is higher when feeding on a fungal food source than when feeding on non-infected plants. In this study we isolated a chitinolytic bacterium from mite homogenate and identified it molecularly as Serratia marcescens (Bizio 1823), which is a model organism for chitin degradation. Precise identification of the bacterium can be important for the development of biological control programs of the mite as well as for further studies investigating Serratia marcescens and its chitinolytic machinery.

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Pister la pyrale: un projet de sciences citoyennes

La pyrale du buis fait des ravages dans les jardins privés et publics de la ville de Neuchâtel. Un groupe interdisciplinaire de chercheurs collabore avec des citoyens pour suivre sa trace et pour réfléchir à des solutions innovantes à ce problème.

Pour en savoir plus, visiter la page du projet.

Chenille de pyrale du buis. Photo: A. Aebi

Chenille de pyrale du buis.
Photo: A. Aebi

The importance of landscape and spatial structure for hymenopteran-based food-webs in an agro-ecosystem

Capture d’écran 2013-08-26 à 10.55.331. Understanding the environmental factors that structure biodiversity and food webs among communities is central to assess and mitigate the impact of landscape changes.

2. Wildflower strips are ecological compensation areas established in farmland to increase pollination services and biological control of crop pests and to conserve insect diversity. They are arranged in networks in order to favour high species richness and abundance of the fauna.

3. We describe results from experimental wildflower strips in a fragmented agricultural landscape, comparing the importance of landscape, of spatial arrangement and of vegetation on the diversity and abundance of trap-nesting bees, wasps and their enemies, and the structure of their food webs.

4. The proportion of forest cover close to the wildflower strips and the landscape heterogeneity stood out as the most influential landscape elements, resulting in a more complex trap-nest community with higher abundance and richness of hosts, and with more links between species in the food webs and a higher diversity of interactions. We disentangled the underlying mechanisms for variation in these quantitative food web metrics.

5. We conclude that in order to increase the diversity and abundance of pollinators and biological control agents and to favour a potentially stable community of cavity-nesting hymenoptera in wildflower strips, more investment is needed in the conservation and establishment of forest habitats within agro-ecosystems, as a reservoir of beneficial insect populations.

Fabian Y, Sandau N, Bruggisser OT, Aebi A, Kehrli P, RE and Bersier LF (in press) The importance of landscape and spatial structure for hymenopteran-based food webs in an agro-ecosystem. Journal of Applied Ecology The importance of landscape and spatial structure for hymenopteran-based food webs in an agro-ecosystem dpi:10.1111/1365-2656.12103

Symbiontes et arthropodes – quelles implications pour la lutte biologique?

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Une version vulgarisée (en français AFS_01_13_F_Aebi et en allemand AFS_02_13_D_Aebi) d’un article paru dans le Journal of Applied Ecology, publiée dans Recherche Agronomique Suisse.

Zindel R, Gottlieb Y, Aebi A. (2011) Arthropod symbiosis, a neglected parameter in pest and disease control programs. Journal of Applied Ecology 48: 864–872

“Cinipide, la lotta biologica funziona” by Luca Berti, in La Regione Ticino

Torymus sinensis, a chinese hymenopteran parasitoid is considered as the only antagonist of the chestnut gall wasp Dryocosmus kuriphilus. After the invasion of the gall wasp in Ticino’s chestnut forests, cantonal authorities sought an homologation of T. sinensis by the Federal Office for the Environment. A very good paper by Luca Berti (published the 4th of July 2012 in La Regione Ticino) summarizes the biosafety questions raised by this classical biological control example and the international situation where different countries regulate the introduction of exotic natural enemies differently. The paper (in italian) can be read here PDF

Torymus sinensis: a viable management option for the biological control of Dryocosmus kuriphilus in Europe?

The chestnut gall wasp Dryocosmus kuriphilus is a global pest of chestnut (Castanea spp). Established as a pest in the mid-twentieth century in Japan, Korea and North America, this species was first reported in Europe in 2002. Following the successful release of a biological control agent Torymus sinensis in Japan, this parasitoid species has been released in Italy since 2005. Here we discuss the potential of T. sinensis as a viable management option for the biological control of D. kuriphilus in central Europe. We suggest that more consideration should be given to determining, (i) the conditions under which T. sinensis may attack alternative native gall wasp hosts and (ii) the likelihood of hybridization of this species with native Torymus. Both issues are central to predicting unassisted range expansion by released T. sinensis, and to assess the environmental risks associated with a more widespread release of this species in Europe.

Melanie Gibbs, Karsten Schönrogge, Alberto Alma, George Melika, Ambra Quacchia, Graham N. Stone and Alexandre Aebi (2011) Torymus sinensis: a viable management option
for the biological control of Dryocosmus kuriphilus in Europe? 56:527–538 DOI 10.1007/s10526-011-9364-8

Is Dryocosmus kuriphilus present in Switzerland? Yes. An evaluation of the use of T. sinensis in Ticino in a socio-economical context can be downloaded here.

Aebi A, Schönenberger N, Bigler F (2011) Evaluating the use of Torymus sinensis against the chestnut gall wasp Dryocosmus kuriphilus in the Canton Ticino, Switzerland. Agroscope Reckenholz-Tänikon Report (ISBN: 978-3-905733-20-4) pp. 71

Arthropod symbioses: a neglected parameter in pest- and disease-control programmes

1. Arthropods are important players in biological control as pests, control agents and transmitters of invertebrate diseases. Arthropods are frequently infected with one or several micro-organisms, serving as micro-ecosystems in which multiple interactions can take place. These micro-organisms include disease agents and symbiotic micro-organisms. The latter are usually vertically transmitted and can have a broad spectrum of effects on their hosts, ranging from reproductive manipulations to protection against natural enemies. These interactions may directly or indirectly alter the biology of many arthropods in agriculturally, medically and ecologically relevant ecosystems.

2. Symbiotic micro-organism-induced reproductive manipulations such as cytoplasmic incompatibility and parthenogenesis induction can substantially affect the rearing of biological control agents. Many insects, and recently also mites and nematodes, have been found to be infected, displaying a wide range of effects. We discuss examples of arthropod-micro-organism interactions and effects,
which could have consequences for the practical application of arthropods in biological control.

3. Symbiotic micro-organisms can also be involved in host protection against natural enemies such as parasitoids, pathogenic bacteria, fungi and viruses.

4. Symbiotic bacteria can influence the vectorial capacity of disease-vectoring arthropods and may be very helpful in decreasing the transmission of disease agents.

5. Synthesis and applications. The effect of micro-organisms on the outcome of biological control programmes is usually not considered in risk assessments and failure analyses. This review emphasizes
the importance of endosymbiotic micro-organisms in comprehensive biological control programmes and provides recommendations on how to recognize, avoid or benefit from these influential tenants.

Zindel R, Gottlieb Y, Aebi A. (2011) Arthropod symbiosis, a neglected parameter in pest and disease control programs. Journal of Applied Ecology DOI: 10.1111/j.1365-2664.2011.01984.x

Detecting arthropod intraguild predation in the field

Picture: Mario Waldburger

The process of biological control carries a distinct risk that an alien biological control agent (BCA) will become established as an invasive alien species with an associated threat to the local ecosystem biodiversity. It is imperative that a wide-ranging environmental risk assessment (ERA) is performed before the release of any BCA. This should include considering various potential but difficult to observe ecological interactions between the BCA and members of the native community, including disruption of intraguild relationships. Detection of intraguild predation (IGP) events involving predatory arthropods in the field can be done by analyzing their gut contents. Polymerase chain reaction (PCR) is a sensitive and specific tool to identify target prey DNA within a predator’s gut. This paper reviews the efficiency of a DNA based approach for detecting IGP in the field, compared with detection by the use of monoclonal antibodies or gas chromatography. Prey specificity, detection times after prey consumption, capacity for quantification, multiple prey targeting and the time and costs involved in developing and using the different methods are considered.

Aebi A, Brown PMJ, de Clercq P, Hautier L, Howe AG, Ingels B, Ravn HP, Sloggett JJ, Zindel R and Thomas A (2011) Measuring arthropod intraguild predation in the field. BioControl 56:429–440 DOI 10.1007/s10526-011-9378-2