Après l'édition de 2011, qui s'est tenue à Wageningen (Pays Bas), puis celle de 2014, qui s'est tenue à Neuchâtel (Suisse), la 16ème édition de la Conférence Internationale sur les relations plante-insecte s'est déroulée du 2 au 6 juillet à Tours (France). A cette occasion, plus de 200 participants se sont retrouvés pour balayer les recherches concernant les relations plante-insecte, que ce soit du point de vue des mécanismes physiologiques que des processus écologiques et évolutifs. Cela a donné lieu à 63 présentations orales et 105 posters. Les actes du colloque seront publiés dans un numéro spécial de la revue Entomologia Experimentalis et Applicata

Nicolas Borowiec a présenté des résultats concernant les dynamiques des populations des parasitoïdes associés au cynips du châtaignier en France.  

Référence:

Borowiec N., Thaon M., Cailleret B., Vercken E. and Ris N (2017). Comparative dynamics of introduced and native parasitoids: the case-study of classical biological control against the chestnut gall wasp in France. 16th International Symposium on Insect-Plant Interaction, 2-6 July 2017, Tours, France (oral communication).

Abstract:

Based on the introduction of an exotic species for its permanent establishment and the long-term control of an agricultural pest, classical biological control can be used as an experimental frame to study the biology of introduced populations in real-life ecosystems. Following the arrival in France in 2008 of Dryocosmus kuriphilus (CGW, Cynipidae), a major pest of Castanea worldwide, a classical biological control program using the exotic parasitoid Torymus sinensis (Torymidae) was implemented in 2011. The first aim of this project was to allow the long-term control of CGW populations, both in commercial orchards and in forests. This project was also a good opportunity to assess ecological mechanisms linked with biological invasions, in particular (i) the role of propagule pressure on the dynamics of T. sinensis and (ii) the ecological changes in communities of native parasitoids induced by the arrival of both exotic species. Between 2011 and 2015, a total of almost 15 000 T. sinensis were released on 58 sites, covering a large geographical area. All of these releases were proven to be highly successful with a rate of establishment of 100%. Dynamics of T. sinensis is characterized by a 4-years exponential increase of population size. The number of individuals introduced did not significantly influenced populations's size or dynamics of T. sinensis. Interestingly, dynamics were similar on sites naturally colonized by T. sinensis but with higher population size, suggesting high propagule pressure from natural populations. Analysis of the dynamics of native parasitoids belonging to the Eupelmus genus showed influence of some ecological factors like habitat connectivity or invasive status of CGW (i.E. core versus front of invasion) but no sign of either positive (e.g. facilitation) or negative (e.g. competition) interaction with T. sinensis. This apparent neutral state may nevertheless change over time when host population size will start decreasing.

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