22 research outputs found
Gestion des populations par piégeage de masse en vergers et étude de la spécialisation d'hôte chez les diptères Tephritidae
Les mouches des fruits de la famille des Tephritidae sont parmi les ravageurs les plus importants des cultures fruitières et légumières dans le monde. C'est notamment le cas en Tunisie où Ceratitis capitata (Diptera : Tephritidae) constitue un frein au développement des cultures fruitières. Dans cette thèse, j'ai testé l'efficacité de différentes méthodes de contrôle de cette espèce. Une détection précoce de la population imaginale avec la para-phéromone "trimedlure" est nécessaire avant l'application d'autres méthodes de lutte. Le bio-insecticide Spinosad est efficace dans la lutte contre C. capitata et représente une bonne alternative à l'insecticide organophosphoré Malathion, mais doit faire partie d'une approche de lutte intégrée incluant des systèmes de bait station et de piégeage de masse. Un système de bait station, constitué d'un attractif alimentaire (hydrolysats de protéines) et d'un insecticide (cyperméthrine), s'est avéré efficace dans la réduction des dégâts sur agrumes et pêchers dans les régions à faible densité de C. capitata. Ce système est également moins nocif que les traitements chimiques vers les insectes non-cibles. Dans les cultures d'agrumes, d'abricot et de figue, les populations de C. capitata ont pu être contrôlées par un système de piégeage de masse contenant un attractif alimentaire à base d'hydrolysats de protéines. De nombreux cas d'invasions de Tephritidae sont connus dans le monde et plusieurs espèces constituent une menace pour la Tunisie. Dans cette thèse, j'ai mis en évidence les liens existants entre sept espèces de Tephritidae et leur gamme de plantes hôtes. Ce travail a permis de déterminer l'effet de la plante hôte sur les différents traits de leur valeur sélective. La hiérarchie observée dans les performances larvaires de chaque espèce de Tephritidae peut être expliquée en partie par la composition biochimique des fruits hôtes. Les espèces oligophages ont une meilleure survie dans les fruits très riches en eau alors que les espèces polyphages ont une meilleure survie dans les fruits riches en sucre, lipide et fibre. J'ai ensuite comparé la niche fondamentale de ces espèces à leur niche réalisée sur le terrain à La Réunion. Pour les sept espèces, la niche fondamentale est plus large que la niche réalisée ; la différence entre les deux niches est plus importante pour les espèces subissant la compétition avec des espèces dominantes sur le terrain. Également, les espèces spécialistes utilisent des plantes hôtes phylogénétiquement proches contrairement aux espèces généralistes. Ces résultats fournissent des informations utiles pour mieux comprendre les risques d'invasion par les insectes phytophages. (Résumé d'auteur
Management of Ceratitis capitata (Diptera: Tephritidae) in Tunisian oases by mass trapping methods
In Tunisia oases, the Mediterranean fruit fly (medfly) Ceratitis capitata affect heavily fruit production. The efficiency of the mass trapping technique based on the use of Cera Trap® was evaluated in two types of oases in the south of Tunisia against C.capitata. Our results showed that in the traditional oasis (mixed orchard), the medfly moves from one fruit specie to another according to their receptivity periods. The population density of medflies started low and peaked three times (16 Jun, 23 Jun, and 7 July) corresponding to the maturation period of apricot fig and peach fruits. The field study showed that medfly population density and rate of fruit damage were significantly lower in figs than in peaches and apricot. Modern oases have later apricot fruit maturity periods than traditional oases, and their medfly populations peaked at 19 Mai. Ceratrap® reduces 2, 2, and 6 times the population density of Mediterranean fruit fly and the rate of damaged fruits compared to untreated plots. These two parameters were twofold less in modern oases than in traditional oases. These results suggest that the use of traps at the density of 70 per ha is sufficient to protect crops under high population densities of C. capitata characterizing the traditional oases agricultural systems
Life History Parameters of Diachasmimorpha longicaudata on Ceratitis capitata Under Laboratory Conditions: Implications for Mass Rearing and Biological Control
The Mediterranean fruit fly, Ceratitis capitata, is considered one of the most destructive pests worldwide. The braconid Diachasmimorpha longicaudata is the most widely used parasitoid in biological control programs of tephritids. It has been mass-reared and used in augmentative releases against major fruit fly species in tropical and subtropical countries, and recently in the Mediterranean Basin. After its introduction into Spain and then Tunisia, reproductive and demographic parameters have been studied on C. capitata under laboratory conditions. These parameters were compared to those published elsewhere. The role of artificial diet for rearing the host is discussed. Our findings showed the good fitness of the parasitoids produced on C. capitata in laboratory with a generation time of 28.1 days, a reproductive rate of 39.2, an intrinsic rate of increase of 0.125, a doubling time of 5.2 days and the finite rate of increase (per day) was 1. Involvements on the biological control of the Mediterranean fruit fly in Tunisia are discussed
Host plant range of a fruit fly community (Diptera: Tephritidae): Does fruit composition influence larval performance?
Background: Phytophagous insects differ in their degree of specialisation on host plants, and range from strictly monophagous species that can develop on only one host plant to extremely polyphagous species that can develop on hundreds of plant species in many families. Nutritional compounds in host fruits affect several larval traits that may be related to adult fitness. In this study, we determined the relationship between fruit nutrient composition and the degree of host specialisation of seven of the eight tephritid species present in La Réunion; these species are known to have very different host ranges in natura. In the laboratory, larval survival, larval developmental time, and pupal weight were assessed on 22 fruit species occurring in La Réunion. In addition, data on fruit nutritional composition were obtained from existing databases. Results: For each tephritid, the three larval traits were significantly affected by fruit species and the effects of fruits on larval traits differed among tephritids. As expected, the polyphagous species Bactrocera zonata, Ceratitis catoirii, C. rosa, and C. capitata were able to survive on a larger range of fruits than the oligophagous species Zeugodacus cucurbitae, Dacus demmerezi, and Neoceratitis cyanescens. Pupal weight was positively correlated with larval survival and was negatively correlated with developmental time for polyphagous species. Canonical correspondence analysis of the relationship between fruit nutrient composition and tephritid survival showed that polyphagous species survived better than oligophagous ones in fruits containing higher concentrations of carbohydrate, fibre, and lipid. Conclusion: Nutrient composition of host fruit at least partly explains the suitability of host fruits for larvae. Completed with female preferences experiments these results will increase our understanding of factors affecting tephritid host range. (Résumé d'auteur
Host plant range of a fruit fly community (Diptera: Tephritidae): does fruit composition influence larval performance?
Population management by mass trapping in orchards and study of host specialization in Tephtitidae diptera
Les mouches des fruits de la famille des Tephritidae sont parmi les ravageurs les plus importants des cultures fruitières et légumières dans le monde. C’est notamment le cas en Tunisie où Ceratitis capitata (Diptera : Tephritidae) constitue un frein au développement des cultures fruitières. Dans cette thèse, j’ai testé l’efficacité de différentes méthodes de contrôle de cette espèce. Une détection précoce de la population imaginale avec la para-phéromone « trimedlure » est nécessaire avant l’application d’autres méthodes de lutte. Le bio-insecticide Spinosad est efficace dans la lutte contre C. capitata et représente une bonne alternative à l’insecticide organophosphoré Malathion, mais doit faire partie d’une approche de lutte intégrée incluant des systèmes de bait station et de piégeage de masse. Un système de bait station, constitué d’un attractif alimentaire (hydrolysats de protéines) et d’un insecticide (cyperméthrine), s’est avéré efficace dans la réduction des dégâts sur agrumes et pêchers dans les régions à faible densité de C. capitata. Ce système est également moins nocif que les traitements chimiques vers les insectes non-cibles. Dans les cultures d’agrumes, d’abricot et de figue, les populations de C. capitata ont pu être contrôlées par un système de piégeage de masse contenant un attractif alimentaire à base d’hydrolysats de protéines. De nombreux cas d’invasions de Tephritidae sont connus dans le monde et plusieurs espèces constituent une menace pour la Tunisie. Dans cette thèse, j’ai mis en évidence les liens existants entre sept espèces de Tephritidae et leur gamme de plantes hôtes. Ce travail a permis de déterminer l’effet de la plante hôte sur les différents traits de leur valeur sélective. La hiérarchie observée dans les performances larvaires de chaque espèce de Tephritidae peut être expliquée en partie par la composition biochimique des fruits hôtes. Les espèces oligophages ont une meilleure survie dans les fruits très riches en eau alors que les espèces polyphages ont une meilleure survie dans les fruits riches en sucre, lipide et fibre. J’ai ensuite comparé la niche fondamentale de ces espèces à leur niche réalisée sur le terrain à La Réunion. Pour les sept espèces, la niche fondamentale est plus large que la niche réalisée ; la différence entre les deux niches est plus importante pour les espèces subissant la compétition avec des espèces dominantes sur le terrain. Également, les espèces spécialistes utilisent des plantes hôtes phylogénétiquement proches contrairement aux espèces généralistes. Ces résultats fournissent des informations utiles pour mieux comprendre les risques d’invasion chez les insectes phytophages.Fruit flies of the Tephritidae family are among the most important pests of fruit and vegetable crops in the world. This is particularly the case in Tunisia where Ceratitis capitata (Diptera: Tephritidae) constitutes a brake on the development of fruit crops. In this thesis, I tested the effectiveness of different methods of control of this species. An early detection of the imaginal population with the para-pheromone "trimedlure" is necessary before applying other control methods. The bio-insecticide Spinosad is effective in the control of C. capitata and represents a good alternative to the organophosphate insecticide Malathion, but must be part of an integrated control approach including bait station and mass trapping systems. A bait station system, consisting of a food attractant (protein hydrolysates) and an insecticide (cypermethrin), has been shown to be effective in reducing damage to citrus and peach trees in areas with low C. capitata densities. This system is also less harmful than chemical treatments to non-target insects. In citrus, apricot and fig crops, C. capitata populations could be controlled by a mass trapping system containing a protein hydrolysate food attractant. Many cases of Tephritidae invasions are known in the world and several species are a threat for Tunisia. In this thesis, I have highlighted the links between seven species of Tephritidae and their host plant range. This work allowed to determine the effect of the host plant on the different traits of their selective value. The observed hierarchy in larval performance of each Tephritidae species can be explained in part by the biochemical composition of host fruits. Oligophagous species have a better survival in fruits very rich in water while polyphagous species have a better survival in fruits rich in sugar, lipid and fiber. I then compared the fundamental niche of these species to their niche realized in the field in Reunion Island. For all seven species, the fundamental niche is larger than the realized niche; the difference between the two niches is larger for species competing with dominant species in the field. Also, specialist species use phylogenetically related host plants unlike generalist species. These results provide useful information to better understand the risks of invasion in phytophagous insects
Enterobactereaceae symbiont as facilitators of biological invasion: review on Tephritidae fruit flies
International audienceInsects harbor a diversity of microbes that are known to affect their host’s response to biotic and abiotic stressors. This is important in the context of climate change and human-caused habitat alterations, during which drastic changes are so rapid that organisms have little time to adapt. Symbionts often accompany invading species, and might play a role in the success or failure of insect invasions. Yet, few studies have examined the evolutionary dynamics and role of gut-associated symbionts at different stages of an insect invasion. We focus on the family Tephritidae (Diptera), which comprises many invasive pest species, and examine how gut-associated bacteria might influence their invasion process based on literature review. Based on our review, we first summarize the prevalence and diversity of gut-associated bacteria harbored by tephritid species. Next, we highlight how those gut communities may influence the fitness of invasive species during the colonization process. We conclude that gut-associated symbionts are highly flexible, and can respond rapidly to changes in biotic and abiotic factors and compensate for limited adaptive capacities of their hosts to counteract these stressors, through changes in the taxonomic composition or prevalence of the community. However, bacteria of Enterobacteriaceae are dominant as well as constitute constant and stable populations in fruit fly gut under different environmental stressors. Our review reveals that this family represents a key bacteria group in all studied tephritid species. This review indicates that knowledge on symbiont–insect interactions is crucial for understanding the success of insect invasion and it should be considered in risk analyses, impact modeling and optimizing invasive pest management
Diet breadth modulates preference - performance relationships in a phytophagous insect community
In most phytophagous insects, larvae are less mobile than adults and their fitness depends on the plant chosen by their mother. To maximize fitness, adult preference and larval performance should thus be correlated. This correlation is not always apparent and seems to increase with the level of specialisation, i.e. specialists have a stronger preference for high quality host plant species compared to generalists. The aim of this study was to test whether the relationship between female preference and larval performance was stronger for specialists than for generalists within a community of fruit flies (Diptera: Tephritidae). A total of six fruit fly species was used, including four generalists, and two specialists co-existing in La Reunion island (France). We estimated oviposition preference through the number of eggs laid and larval performance through the larval survival on 29 different host plants species belonging
to 15 families in the laboratory and evaluated the relationship between these two traits. Preference-performance relationship differed according to the degree of specialisation with a strong positive correlation for specialists and no relationship for generalists. These results substantiate the theory that choosing high quality hosts is more important for specialists that are adapted to survive on fewer host plants than for generalists