We report here for the first time the presence ofOphelimus mediterraneussp. n. in Mediterranean Europe. This species appears to be closely related toOphelimus maskelli, a well-known invasive pest ofEucalyptus. Based on molecular (cytochrome oxidase I, 28S), morphological (multivariate ratio analysis) and bio-ecological investigations, our study gives unambiguous relevant criteria that allow the discrimination between these two species. A full description ofO. mediterraneussp. n. is also provided. The geographic distribution ofO. mediterraneussp. n. as well as its impact onEucalyptusspecies needs to be more widely assessed since its presence may have been confused withO. maskelliin their sympatric introduced areas. Further investigations of potential parasitoids in the native area may thus be welcomed to evaluate classical biological control achievability.

The spotted wing Drosophila, Drosophila suzukii (Ds), became a major economic pest for fruit production since its establishment in Europe and America. Among potential control methods, only classical biological control appears to be a mean of sustainably regulating Ds in both cultivated and natural habitats. In the frame of risk assessment, pre-release surveys were carried out in a restricted but highly heterogeneous area in the south-east of France using traps and deliberate field exposures of Ds and D. melanogaster larvae/pupae. Although Ds abundance varied according to sampling methods, it was found to be pervasive and to produce offspring and adults in most conditions (spatial and seasonal). Its main limits are some specific abiotic conditions (i.e., desiccation) as well as interspecific competition. Indeed, Ds mostly co-occurred with D. busckii and D. hydei, probably due to common phenology and/or ecological requirements. These two species thus deserve more attention for risk assessment. The main indigenous parasitoids collected belonged to two pupal species, Trichopria cf drosophilae and Pachycrepoideus vindemmiae, but their presence was observed late in the autumn and mainly in cultivated areas. Results are discussed in a comparison of the methodological approaches for monitoring Drosophilids and the benefits-risks assessment of classical biological control.

In response to the introduction and spread of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae) in metropolitan France, including Corsica, the exotic parasitoid Torymus sinensis Kamijo (Hymenoptera: Torymidae) was deliberately introduced in more than 50 locations covering most of the areas of chestnut production. To test the impact of propagule pressure (i.e., the number and size of introductions) on establishment success and post‐release dynamics, the introductions were done according to three experimental modalities: (1) a single introduction of 100 females, (2) two sequential introductions of 50 females, or (3) a single introduction of 1 000 females. Post‐release surveys demonstrated a very high local establishment of T. sinensis, regardless of the introduction modality. Post‐introduction dynamics were found to follow a two‐phase process. First, early dynamics were characterized by an exponential growth of T. sinensis populations without a significant decrease in D. kuriphilus populations. Later, middle‐term dynamics indicated a global decrease in both D. kuriphilus and T. sinensis populations. Quite surprisingly, propagule pressure had a limited effect on post‐introduction dynamics, with a lasting demographic advantage for the largest introductions, but no influence of the number of introductions. Finally, site connectivity had a positive effect on T. sinensis population size, suggesting successful colonization and establishment at a wide spatial scale beyond the introduction sites. In addition, we observed that some T. sinensis exhibited a very short developmental time compared to the majority of the emerged individuals, which may be interpreted as a diversified bet hedging strategy against environmental stochasticity. These findings confirm the strong potential of T. sinensis for successful establishment and sustainable control of the chestnut gall wasp in Europe.

1. The invasive pest Drosophila suzukii is a fruit fly native to Asia that infests a wide variety of fruits. Wild plant species are major reservoirs for D. suzukii populations but their infestation rates vary greatly among geographical areas.2. We aimed at disentangling the relative roles of macroclimatic, landscape and local factors in the rate of D. suzukii infestation of elderberry fruits (Sambucus nigra), a major wild host plant in Europe.3. We collected elderberry fruits across 215 sites distributed in 13 regions from North to South of France. We counted the number of emerging D. suzukii adults and

When an invasive species establishes in a new area and reaches high densities, some antagonists may benefit from this bonanza situation. How such a newly formed community may then be challenged after the regulation of the invaders by external outputs -e.g. the deliberate introduction of specialized natural enemies -remains however poorly documented. To investigate this issue, we used the case study of the invasion of the Asian chestnut gall-wasp Dryocosmus kuriphilus Yasumatsu in France and its subsequent control by the exotic parasitoid Torymus sinensis. From the survey of 26 locations during 5 years after the T. sinensis introduction, we analyzed how the patterns of co-occurrence between the different native parasitoid species changed through time. Our results demonstrate that native parasitoid communities experienced increased competition as the D. kuriphilus levels of infestation decreased. During the last year of the survey, two alternative patterns were observed: either native parasitoid communities were almost inexistent, or they were finally dominated by one main parasitoid: Mesopolobus sericeus. We observe that the two patterns correlate with the habitat and that they may be explained by environmental features such as differences in the initial states of the native community structure. These results highlight how the "boom-and-bust" dynamics of an invasive pest followed by successful biological control can deeply alter the structure of native communities of natural enemies.

Native to China, the chestnut gall wasps Dryocosmus kuriphilus Yasumatsu (Hymenoptera, Cynipidae) has invaded several countries on three continents in about half a century. To reduce the negative impact on the chestnut industry, the hymenopteran parasitoid Torymus sinensis Kamijo (Hymenoptera, Torymidae) was firstly translocated from China to Japan and then from Japan to other countries. From an agronomic point of view, this classical biological control programme is perceived as a great success story even if in Japan it was overshadowed by evidence of hybridisation with the indigenous species Torymus beneficus Yasumatsu & Kamijo. Based on numerous specimens collected in France and Italy but also in Asia, as well as on published data, we detected molecular and phenotypic signatures of a possible hybridisation. Our results evidenced for the first time that the European stock of T. sinensis has some rare molecular signatures of historical hybridisation that took place in Japan (0.66% of the mitochondrial haplotypes). Our morphometric study also shows that European and Japanese T. sinensis are morphologically intermediate between the two species that hybridised. The identity of the early‐ and late‐season strains of T. beneficus is discussed. Torymus beneficus late‐season strain (TbL) is considered to be the same as T. sinensis and only the early‐season strain (TbE) is the true T. beneficus. Torymus beneficus is morphologically very close to T. sinensis, and the interspecific distance of COI, though large, is comparable with the larger intraspecific variability found in other Chalcidoidea species. Though the two could be regarded as subspecies, for the stability of nomenclature it is better to continue treating them as distinct species.

Pseudaulacaspis pentagona provoque d'importants dégâts sur cassissier en Isère. Un inventaire des ennemis naturels a été dressé. Bien que l'on constate la présence de parasitoïdes, leur efficacité semble limitée.

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