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Annona senegalensis Pers. (Annonaceae) is a wild shrub used multipurposely in food and traditional medicine by local people in African tropical countries. During its fruiting period, especially at the green fruit stage, this plant harbors an important community of insects such as the planthopper Hilda undata (Tettigometridae) and various ant species (Formicidae). This study aimed at understanding the interactions between ants, Hilda undata and the plant Annona senegalensis. Green fruit insect visitors of A. senegalensis were collected randomly from 30 green fruits of 30 plants per site, at four sites across the Sudanian and Sudano-Sahelian climatic zones of Burkina Faso during the green fruit stage of the plant, from June to July. The behavior of green fruit visiting insects was observed in the field. In addition, ants and Hilda undata were collected and their whole body sugars were analyzed. Ants were the most recorded visiting insect group, representing up to 95% of the insects observed on the fruit. The orders of insects recorded were Coleoptera, Diptera, Hemiptera, Hymenoptera and Lepidoptera and the most frequently encountered species were Trichomyrmex abyssinicus, Crematogaster sp (Formicidae), Messor galla (Formicidae), Brachyponera sennaarensis (Formicidae) and H. undata. Behavioural observations showed that ants consume extrafloral nectar from green fruits and honeydew from H. undata. The ants would protect the green fruits from their pests and H. undata from its natural enemies. This study is the first report highlighting mutualistic interactions between A. senegalensis, ants and H. undata.

The pollination syndrome of the African custard apple (Annona senegalensis Pers.; Annonaceae) was investigated to gain insights into the reproductive strategy of this multipurpose wild shrub. Flower visitors were collected and frequently surveyed in the morning on 30 flowers of 30 plants per site, at four sites across the Sudanian and Sudano-Sahelian climatic zones of Burkina Faso during the flowering season, from May to June. A total of nine species of insects including Coleoptera (Curculionidae, Scarabeidae), Hymenoptera (Formicidae) and Diptera (Tephritidae) were observed visiting flowers. Among the recorded insects, two sympatric species of weevil (Curculioninae, Ochyromerini, Endaeus cf. floralis and Endaeus sp.) were by far the most abundant (97% of specimens) and were observed on all the 120 flowers sampled. Both species were observed on the fleshy petals of the cantharophilous flowers of Annona senegalensis that they use as substrate for the development of larval stages. These observations echo with the ever-growing number of researches highlighting the major role of weevils in the pollination of the pantropical Annonaceae. Our study provides first evidence of brood-site mutualism between an Annonaceae species and its specialized weevils pollinators.

Diversifying agroecosystems through habitat management inside or outside production fields can provide alternative hosts and/or prey for natural enemies. In semi-natural habitats, parasitoids may find alternative host-plant complexes (HPC) that could allow their development when pest hosts are scarce in the field. However, morphological and physiological differences between alternative and targeted HPCs could affect the preference and fitness of the parasitoids, possibly altering their efficacy in regulating pests. In the present study, we examined two Aphelinus mali parasitoid populations developing on Eriosoma lanigerum from two host plants (Malus domestica-apple trees and Pyracantha coccinea). We hypothesized that A. mali from both HPCs will show different life history traits and behaviors because primary and alternative host-plants are known to induce variations in parasitoid biological performance. Our findings indicate that A. mali originating from E. lanigerum on P. coccinea parasitized more aphids and are smaller than those originating from E. lanigerum on apple. Furthermore, these parasitoids did not significantly vary their ability to attack and oviposit apple E. lanigerum, suggesting that P. coccinea could function as a suitable banker plant for A. mali. We discuss the potential use of P. coccinea in conservation biological control of E. lanigerum in apple orchards.

International audience; There are many different practices that contribute to conservation biological control, but little is known about their complementarity. We tested the effects of providing food and alternative hosts to parasitoids by intercropping a plum orchard with companion plants. Oats and vetch were intercropped into the orchard either as single-species (oats or vetch) or two-species (oats and vetch combined) intercrops within an inter-row. The trophic resources provided by these intercrops were assessed, along with the incidences of aphids and their parasitoids in plum trees. We found up to ten alternative host species provided by oats and vetch, and extrafloral nectar was available from the vetch and mixed strips. An effect of intercrop type and distance to plum trees was observed on aphid incidence during one sampling period. Parasitism rates in exclusion cages were affected by intercrop type, reaching almost 60% close to the mixed intercrop. However, no general tendency was observed upon whether oats, vetch or their mixture was associated with a lower incidence of aphids. We found no evidence that providing effective sources of food and alternative hosts for parasitoids increased aphid mortality in this study. The context-dependent efficiency of intercropping is discussed.

All data presented and scripts needed to reproduce analyses can be found on the following repository: https://github.com/MartinLuquetEcology/Parasitoid-sugar-feeding-and-parasitism-in-intercrops.; International audience; The nectar provision hypothesis predicts that the introduction of nectar-producing plants in agroecosystems benefits parasitoid populations in the field and enhances biological control. Intercropping is a common crop diversification scheme that may bring complementary nectar sources for parasitoids and increase herbivore pest control. For instance, intercropping cereals with faba beans introduces nectar sources in usually sugar-devoid systems (i.e. cereal single crops). However, the nectar provision hypothesis has never been evaluated at the field scale in such intercropping systems. To test this hypothesis, we evaluated if sugar is a limiting factor for Aphidius parasitoids in single triticale crops and if their nectar feeding activity increases in faba bean-triticale intercrops. Aphidius feeding patterns were evaluated from their sugar profiles, using high-performance liquid chromatography (HPLC). In parallel, aphid density and parasitism rates were estimated at the edge and in the centre of single crops and intercrops. Sugar analyses revealed that honeydew was always the main sugar source for parasitoids, and although a significant proportion of parasitoid populations were recorded to feed on nectar, this proportion did not increase in intercrops. Besides, parasitism rates did not increase in intercrops, nor were aphid populations reduced. Thus, our results do not support the nectar provision hypothesis, but rather suggest that although nectar provision benefits parasitoid populations in some systems, its effects on biological control are highly context-dependent. They also confirm that honeydew can be a major food source for parasitoids, which may not necessarily be sugar limited at the field scale.

International audience; Experience of host-associated olfactory stimuli during development affects subsequent foraging decisions in many parasitoids, leading to host fidelity. We have recently shown that odours emitted by an alien host-plant complex (HPC) may affect this learning process. However, the consequences of this olfactory experience on parasitoid host foraging decisions is unknown. Here, we investigated if olfactory preferences induced by experience might drive parasitoid HPC choice and oviposition decisions. We presented two HPCs in dual choice experiments to Aphidius ervi females that had been reared on each HPC, either in a simple (one HPC) or complex (two HPCs) olfactory environment. HPC choice, time before landing on a HPC and number of aphid attacks were recorded. Early experience had contrasting effects on each of these parameters. Regardless of their origin, parasitoids did not land preferentially on any HPC, but they more frequently attacked one of the two hosts (Acyrthosiphon pisum) once they had landed on its HPC. Females emerging from the A. pisum/faba bean HPC attacked more aphids, regardless of the host species. Finally, the olfactory complexity of the environment had inconsistent effects on foraging decisions. These observations, contrasting with previous results obtained in olfactometer assays, indicate that olfactory preferences induced in early stages are not sufficient to predict parasitoid oviposition decisions. Moreover, the integration of multiple signals at several scales might generate different foraging patterns at each step of the host selection process.

Session 17. Tools to design, manage and monitor diversified systems from the field to the landscape levels; International audience

International audience; Insect populations are prone to respond to global changes through shifts in phenology, distribution and abundance. However, global changes cover several factors such as climate and land-use, the relative importance of these being largely unknown. Here, we aim at disentangling the effects of climate, land-use, and geographical drivers on aphid abundance and phenology in France, at a regional scale and over the last 40 years. We used aerial data obtained from suction traps between 1978 and 2015 on five aphid species varying in their degree of specialization to legumes, along with climate, legume crop area and geographical data. Effects of environmental and geographical variables on aphid annual abundance and spring migration dates were analyzed using generalized linear mixed models. We found that within the last four decades, aphids have advanced their spring migration by a month, mostly due to the increase in temperature early in the year, and their abundance decreased by half on average, presumably in response to a combination of factors. The influence of legume crop area decreased with the degree of specialization of the aphid species to such crops. The effect of geographical variation was high even when controlling for environmental variables, suggesting that many other spatially structured processes act on aphid population characteristics. Multifactorial analyses helped to partition the effects of different global change drivers. Climate and land-use changes have strong effects on aphid populations, with important implications for future agriculture. Additionally, trait-based response variation could have major consequences at the community scale.

International audience; Parasitic wasps are prominent natural enemies of crop pests. They usually feed on floral resources during the adult stage (nectar, pollen, or honeydew). Extrafloral nectar is an alternative source of sugar easily accessible to adult parasitoids. We developed an original method of nectar labelling based on the injection of labelled sugar solution into the plant stem in order to analyse the nectar uptake by parasitoids (cotton wick method). This method was used to artificially enrich extrafloral cornflower, Centaurea cyanus L. (Asteraceae), nectar with the stable isotope C-13. We analysed (1) the transfer of C-13 from the sugar solution into extrafloral nectaries, (2) the uptake of labelled nectar by parasitoids under laboratory conditions, and (3) the ability of the method to discriminate, in an oilseed rape (Brassica napus L., Brassicaceae) field, between labelled parasitoids (i.e., those who have fed on labelled cornflowers located adjacent to the field) and unlabelled parasitoids to track parasitoid movements from the margin into the field. The extrafloral nectar of all test plants was C-13-labelled. Most (66%) of the parasitoids were identified as marked after 96h of exposure to labelled plants in the laboratory. We could also detect labelled parasitoids inside the field, but the detection rate was only 1%. The experiments clearly demonstrate that the cotton wick method is appropriate to label extrafloral nectar and parasitoids feeding on this labelled nectar. Further research is needed on the amount of labelled extrafloral nectar required to obtain a sufficient marker level to track parasitoid movements in the field.

International audience; Semi-natural structures of agricultural landscapes are known to provide important habitat functions for natural enemies of crop herbivores. Although several functions such as resource and shelter are related to plant species, the role of the floristic composition is not well understood. Using a correlative approach, we analysed interactions between plant functional groups of spontaneous field margin vegetation and the regulation of crop herbivores. We further compared the influence of the local plant community with that of landscape structure at different scales (50-500 m). We used Brassica oleracea crop plants as phytometers planted into field margins of 48 fields and observed correlations of explanatory variables (vegetation, landscape) and response variables (herbivore and natural enemy abundance, crop damage) for two consecutive years (24 fields x year(-1)). We observed significant positive and negative correlations between plant functional groups and variables related to crop herbivore regulation. In general, plant cover based-models provided a better fit than diversity-based models. Entomophilous flowering plants providing nectar showed a positive correlation to ladybird abundance and aphid parasitism and a negative relationship with major crop plant damage caused by leaf-chewing invertebrates. Cover and diversity of wild Brassicaceae species were positively correlated with flea beetle damage and abundance. Most correlations with plant functional groups remained significant after fitting variables of landscape structure. The density of semi natural habitats showed predominantly positive correlations to crop herbivore regulation, whereas the density of crops was negatively correlated. The number of significant relationships decreased from natural enemy to herbivore abundance and to plant damage. Our results demonstrate the relative importance of field margin vegetation for crop herbivore regulation. The differential responses to plant functional groups support the idea that designing specific plant mixtures may improve biological control. Additional effects of landscape variables suggest that a combination of local and landscape-scale management is the most promising strategy to optimise this ecosystem service. (C) 2016 Elsevier B.V. All rights reserved.

International audience; The efficiency of the biological controlstrategies based on parasitoids, either as a release or a conservative measure, depends on the timely arrival or release of the parasitoids after colonization of the field by the pest. In this study, the effects of the delay between the cabbage aphid Brevicoryne brassicae (Hemiptera: Aphididae) infestation and the release of its parasitoid Diaeretiella rapae (Hymenoptera: Braconidae) and of the number of parasitoid releases on aphid population dynamics and host plant growth were investigated. When the parasitoids were released at the start of the infestation, 89.6 % of the aphids were parasitized one month later, and the damage to cabbage was low. The identical number of parasitoids released two weeks after the start of the infestation partially controlled the aphid population, but the growth of the cabbage was altered. The earliest introduction of the parasitoid to the crop led to an efficient host regulation, and the release in three times rather than in one time did not improve the control efficiency at this release delay. The implications for biological control strategies that use parasitoids of aphids are discussed.

International audience; The recognition and avoidance of already parasitized hosts is a major issue in parasitoid behavioral ecology, particularly for solitary species. Superparasitism avoidance is often described as an adaptive strategy, and the discrimination abilities of parasitized hosts have been selected in many species. The recognition of parasitized hosts often relies on olfactory cues or a marking pheromone that could decay with the time between successive host encounters. The intraspecific discrimination abilities of the solitary parasitoid Anisopteromalus calandrae (Hymenoptera: Pteromalidae) have been studied in the laboratory under several conditions. While the discrimination abilities of recently parasitized hosts and those parasitized for a longer time (i.e. when the first egg is about to hatch) are known in this species, their capacity to discriminate hosts containing eggs at intermediate stages and their capacity to adapt superparasitism avoidance depending on the identity of the first female has not been explored. The present study investigated (i) females' behavior in the presence of hosts parasitized by themselves or conspecifics with varying time intervals, and (ii) whether these females were able to adapt their reproductive strategy when placed in a choice and a no-choice situation. Our experiments confirmed that A. calandrae females are able to discriminate between parasitized and unparasitized hosts, as they laid more eggs on the latter. However, they did not recognize hosts containing eggs of a conspecific at intermediate developmental stages, when placed in either a choice or a no-choice situation. The same phenomenon was observed in a self-superparasitism situation in a choice experiment. By contrast, in a no-choice situation, they recognized hosts containing eggs that had been freshly laid by themselves, but not those at an intermediate stage of development.

International audience; Leaf colour and leaf area are key parameters for many plant studies, including plant protection. The quantification of foliar bleached area is often used to evaluate the strength of plant attack by pests or diseases, to compare the efficiency of different treatments, the resistance of some populations, and to set up some control methods. The quantification of such area by human vision often lacks accuracy and reliability. Image analysis systems could bring a more accurate and objective measure, and could be automated to treat a great number of samples. Such an automated tool has been developed in order to measure quantitatively foliar bleaching due to the sycamore lace bug, Corythucha ciliata (SAY) on Plane tree. This tool was built up with a colour image capture bench and a fast automated segmentation process based on an original chlorophyll histogram unsupervised classification. Dedicated software was developed and integrated in an operational image processing platform capable of routine use by non-specialists in image analysis. The accuracy of the tool was determined by comparison to human expert segmentation. A very low error rate was observed in the absence of artefacts, but artefacts such as powdery mildew symptoms were not well distinguished and lead to weaker performance. Comparing its reliability and robustness to classical visual estimation and classification method, the tool performance was similar to the most experienced rater. The advantage of such a system is the possibility to treat automatically a large number of pictures and produce accurate, reliable, repeatable and non-subjective quantitative measurements.

Eupelmus vuilleti acts as a cleptoparasitoid when encountering a host parasitized by Dinarmus basalis. The encounter of a parasitized host stimulates an increasing number of ovipositor probes directly above the parasitized host, an increasing number of host stings and the destruction of approximately 40% of the D. basalis eggs. The stimulation of ovipositor probes appears to be due to the detection of a stimulus that is different from the stimulus allowing interspecific host discrimination. It appears that a proteinacious substance produced by the D. basalis venom gland and deposited on the edge of the drilled hole induces probing behaviour of E. vuilleti.

International audience; In the adult stage, many parasitoids require hosts for their offspring growth and plant-derived food for their survival and metabolic needs. In agricultural fields, nectar provisioning can enhance biological control by increasing the longevity and fecundity of many species of parasitoids. Provided in a host patch, nectar can also increase patch quality for parasitoids and affect their foraging decisions, patch time residence, patch preference or offspring allocation. The aim of this study was to investigate the impact of extrafloral nectar (EFN) provisioning close to hosts on parasitoid aggregation in patches. The aphid parasitoid Diaeretiella rapae (M’Intosh) was released inside or outside patches containing Brassica napus L. infested by Brevicoryne brassicae L. aphids and Vicia faba L. with or without EFN. When parasitoids were released outside patches, more parasitoids were observed in patches with EFN than in patches deprived of EFN. This higher recruitment could be linked to a higher attraction of a combination of host and food stimuli or a learning process. A release–recapture experiment of labeled parasitoids released within patches showed the higher retention of parasitoids in patches providing EFN and hosts, suggesting that food close to the host patch affects patch residence time. Both attractiveness and patch retention could be involved in the higher number of parasitoids foraging in host patches surrounded by nectar and for the higher parasitism recorded. Nectar provisioning in host patches also affected female offspring allocation inside the patch.

Biol. ControlISI Document Delivery No.: 137WETimes Cited: 0Cited Reference Count: 57Jamont, Marie Crepelliere, Solene Jaloux, Brunoregion Pays-de-la-Loire [2008-8512]We thank Michele Travers for technical help, Pascale Satour for HPLC analyses (University of Angers, France) and Donna Niemann for manuscript revision. We acknowledge the region Pays-de-la-Loire (contract # 2008-8512) for financial support to the project INTRANBA (INteractions TRophiques et systemes de culture innovants economes en intrANts: application a l'utilisation des legumineuses dans les cultures de BrassicAcees).Academic press inc elsevier scienceSan diego; International audience; Plant derived-food is an important food source for natural enemies. We conducted laboratory tests to evaluate the suitability of extrafloral nectar (EFN) from Vicia faba as a potential food source for female Diaeretiella rapae in an intercropping context, and how EFN affects the survivorship and progeny production in this species. Extrafloral and floral nectar have a similar sugar composition, a highly nutritious food for parasitoids. Under controlled conditions, intercropping V. faba with Brassica oleracea had no impact on V. faba EFN sugar composition. Female parasitoids lived significantly longer when provided with EFN (14 days) than when provided with water (4 days), honeydew (4 days), and honey and water (9 days) or when they were without food (3 days). The longevity of females provided with EFN did not differ in the absence or presence of aphids. The numbers of hosts parasitised and offspring produced per female over the course of her lifespan were significantly increased by placing a V. faba plant next to a B. oleracea plant. However, this increase was observed for both nectary-bearing and nectary-less V. faba plants. Feeding on EFN resulted in an increase in the length of the oviposition period, which was primarily concentrated during the first four days of the life of the female. No impacts of V. faba EFN provision were observed on offspring larval survival, sex ratio or size. These results suggest that provision of EFN can increase both the rate of parasitism and parasitoid survival without hosts. (C) 2013 Elsevier Inc. All rights reserved.

Prédation des pucerons par un cortège d’ennemis naturels sur Brassicacées légumières : quantification et facteurs de variation à l’échelle du paysage agricole

Structure du paysage en parcelles de Brassicacées : impact sur les insectes phytophages et leurs ennemis naturels.

Structure du paysage et colonisation des parcelles de Brassicacées légumières par les insectes phytophages et leurs ennemis naturels

Oogenesis of the parasitoid wasp Eupelmus vuilleti is known to be dependent on host availability. However, examination of ovarian dynamics by microscopy showed that oogenesis and vitellogenesis are initiated before female eclosion and proceed 1-2 days after, independent of host presence. Oogenesis continued beyond the 2nd day only in the presence of hosts, otherwise it was replaced by egg resorption. It is thus possible to distinguish between host-independent and host-dependent periods of oogenesis. In the presence of host, each ovariole (three per ovary) contained generally three oocytes: a fully mature oocyte, a nearly mature one and an immature one. However, host deprived-females resorbed their most mature and their smallest oocytes, but kept one almost mature oocyte per ovariole. Comparison of zero, short and long host deprivation periods showed that females always had the ability to quickly lay eggs to exploit any new host. However, increased deprivation led to a reduction in the number and the viability of eggs. Enzymo-immunological measurements of ecdysteroids were made in whole females, in dissected ovaries and in newly laid eggs. Our results indicated that ecdysteroids play a major role as circulating hormones involved in the regulation of oogenesis.

Eupelmus vuilleti (Hymenoptera; Eupelmidae) is a solitary ectoparasitoid producing yolk-rich eggs. The female oviposits mainly on the fourth larval instar of Callosobruchus maculatus (Coleoptera; Bruchidae), which develop within pods and seeds of Vigna unguiculata (Fabacae). Parasitoid females are synovigenic, i.e., they are born with immature eggs and need to feed from the host to sustain egg production during their entire lifetime. However, eggs are rapidly resorbed in unfavourable conditions and an efficient stop-and-go mechanism controls oogenesis in such animals. In this study, the possible involvement of ecdysteroids in the regulation of parasitoid oogenesis is examined. In a first step, the identity and titre of ecdysteroids in reproductively active and inactive female parasitoids were investigated by high performance liquid chromatography followed by enzyme immuno-assay (EIA/HPLC). A larger secretion of ecdysone was found in female during their reproductive period compared with inactive females. In a second step, both the secretion of ecdysteroids into the medium of in vitro incubated ovaries and the ecdysteroid content of females reared with or without host were measured (EIA). The presence of the host, which represents both the oviposition site and the nutritional source, induced an active biosynthesis of ecdysone. This synthesis started at a slow rate after host introduction and reached a maximum after 48 h. When hosts were available, this synthesis was cyclic and continuous during the entire female lifetime. These results showed that host presence triggered ovarian synthesis of ecdysteroids, which are involved in a stop-and-go regulation of egg production linked to host availability.

Reunion Island has been suffering a re-emergence of Huanglongbing (HLB) for the last 10 years after successfully controlling this deadly citrus disease in the 1970s/1980s. HLB is caused by bacteria of the genus Candidatus Liberibacter and is transmitted by psyllids (all considered as regulated pests). To limit the spread of HLB an epidemiological surveillance network was set up on the island in 2015. This surveillance is the result of interaction between a few key stakeholders from various authorities: DAAF (manager), FDGDON (plant and animal health-related organisation and approved laboratory), ANSES (reference laboratory), CIRAD (research) and professionals. This tension in human resources and the important organisational freedom specific to surveillance in the French overseas territories make this network a relevant object of study. The assessment of the surveillance network is critical. The OASIS semi-quantitative evaluation method, developed by the ANSES in 2010, was applied to this system. Thirty semi-structured interviews and numerous meetings were used to characterise the effectiveness of the surveillance system and assess its performance, including the formalisation of objectives and the use of data collected. This evaluation process (collection, measurement, and assessment) made it possible to identify areas of weakness and provide recommendations to improve the surveillance and epidemiological risk management of the disease.; La Réunion subit une réémergence du Huanglongbing (HLB) depuis une dizaine d’années après avoir réussi à contrôler cette maladie mortelle des agrumes dans les années 70-80. Afin de limiter la propagation du HLB, occasionnée par des bactéries du genre Candidatus Liberibacter transmises par des psylles (tous considérés comme organismes nuisibles réglementés), un dispositif de surveillance épidémiologique du HLB a été mis en place sur l’île en 2016. Cette surveillance est le fruit d’interactions entre quelques acteurs clés issus d’instances aux missions diverses : DAAF (gestionnaire), FDGDON (OVS et laboratoire agréé), ANSES (laboratoire de référence), CIRAD (recherche) et professionnels… Cette tension en moyens humains et la forte liberté organisationnelle propre à la surveillance ultramarine font de ce dispositif un objet d’étude pertinent. L’évaluation du fonctionnement des dispositifs d’épidémiosurveillance est fondamentale. La méthode d’évaluation semi-quantitative OASIS, développée par l’ANSES en 2010, a été appliquée à ce dispositif. A travers une trentaine d’entretiens semi-directifs et de nombreuses concertations, nous avons caractérisé le fonctionnement du dispositif de surveillance et évalué sa performance de la formalisation des objectifs à l’utilisation des données collectées. Ce processus évaluatif (récolte, mesure et jugement) a permis d’identifier des pistes d’amélioration en ciblant les limites du dispositif actuel. Ainsi, des recommandations ont été préconisées pour améliorer la surveillance et la gestion des risques épidémiologiques de cette maladie.

The cucurbit beetle, Aulacophora fauveli, is the main insect pest of vegetable crops on Wallis and Futuna territory. Preferentially attacking cucurbit crops, this pest is the most problematic and the one causing the most damage. The efficacy of sustainable methods to control Aulacophora was tested in a cucurbit crop association. A field trial compared a physical control (shade net) with two plant extracts (neem leaf (Azadirachta indica) slurry and bush passion fruit leaf (Passiflora foetida) slurry) and an untreated control. With a very low pest pressure, no difference has been found between treatments on the number and damage of pumpkin beetle. However, the use of the treatments resulted in higher production than the untreated control. In addition, the use of a wood chip mulch and the use of the shade net provided favourable conditions for good plant development. Further experiments should be carried out on Wallis to determine in a conclusive way the means of effective control of the cucurbit beetle.; La chrysomèle des cucurbitacées, Aulacophora fauveli, est le principal insecte ravageur des cultures maraîchères sur le territoire de Wallis-et-Futuna. Attaquant préférentiellement les cultures de cucurbitacées, ce ravageur est la problématique majoritaire ; il occasionne le plus de dégâts. L’efficacité de plusieurs méthodes de lutte alternative pour contrôler la chrysomèle ont été testées dans une association culturale de cucurbitacées. Un essai en plein champ a comparé une lutte physique (filet d’ombrage) à deux préparations naturelles issues de plantes (purin de neem (Azadirachta indica) et de passiflore (Passiflora foetida)) et un témoin non traité. Avec une pression en ravageur très faible, aucune différence n’a été mise en évidence entre les différents traitements sur le nombre et les dégâts faits par les chrysomèles. Toutefois, l’utilisation des traitements a permis d’obtenir une production supérieure à celle du témoin non traité. De plus, l’utilisation d’un paillage de copeaux de bois et l’utilisation du filet d’ombrage induisent des conditions favorables au bon développement des plants. De nouvelles expériences seraient à mener sur Wallis pour déterminer de façon significative des moyens de lutte efficace contre la chrysomèle des cucurbitacées.

Tomatoes are one of the main market gardening crops in Mayotte. It is mainly cultivated in the open field during the dry season. Despite its economic importance, production is fragile, yields are 8 times lower than those of the mainland. The main cause of these losses are pests. The main tomato pests are Neoceratitis cyanescens, Helicoverpa armigera and Tuta absoluta. These last two insects are considered more secondary. The main means of controlling these insects is chemical control. However, in Mayotte the latter is intensive and unreasonable and it is the cause of significant health and environmental problems. The objective of this study is to test the efficacy of kaolin against, mainly Neoceratitis cyanescens, but also against, Helicoverpa armigera and Tuta absoluta. Initially, the air blast sprayer was configured using water-sensitive paper to ensure that a satisfactory application of kaolin will be obtained during the treatments. Then, the number and weight of fruits, whether marketable or not, harvested from the beds treated with kaolin, insecticide (Decis Protech®) and untreated beds, were measured. Analysis of the results showed a decrease in losses associated with Neoceratitis cyanescens on kaolin treated plants compared to other modalities. However, this reduction is not satisfactory. Regarding Helicoverpa armigera and Tuta absoluta, kaolin did not show any difference compared to the insecticide treatment and the control.; La tomate est une des principales cultures maraîchères à Mayotte. Elle est principalement conduite en plein champ pendant la saison sèche. Malgré son importance économique, la production est fragile, les rendements sont 8 fois inférieurs à ceux de la métropole. La principale cause de ces pertes sont les bioagresseurs. Les principaux ravageurs de la tomate sont Neoceratitis cyanescens, Helicoverpa armigera et Tuta absoluta. Ces deux derniers insectes sont considérés comme plus secondaires. Le principal moyen de lutte contre ces insectes est la lutte chimique. Cependant, à Mayotte cette dernière est intensive et déraisonnée et est cause de problèmes sanitaires et environnementaux importants. L’objectif de cette étude est de tester l’efficacité du kaolin contre, principalement Neoceratitis cyanescens, mais aussi contre, Helicoverpa armigera et Tuta absoluta. Dans un premier temps un paramétrage de l’atomiseur a été opéré à l’aide de papier hydrosensible afin de garantir l’obtention d’une application de kaolin satisfaisante lors des traitements. Ensuite, le nombre et le poids des fruits commercialisables ou non, récoltés sur les planches traitées au kaolin, à l’insecticide (Decis Protech®) et non traitées, ont été mesurés. L’analyse des résultats a montré une baisse des pertes liées à Neoceratitis cyanescens sur les plants traités au kaolin par rapport aux autres modalités. Cependant, cette réduction n’est pas satisfaisante. Concernant, Helicoverpa armigera et Tuta absoluta, le kaolin n’a pas montré de différence par rapport au traitement insecticide et au témoin.

Blackcurrant cultivation represents a small surface in France (2500 hectares), but it sustains a whole sector mainly based on transformation. Since the years 2000, all the French production areas are infested by Pseudaulacaspis pentagona (Targioni Tozzeti 1886), a very polyphagous, widely distributed diaspid scale. It’s damages on blackcurrant bushes are important, to the point of threatening the whole sector. Confronted with the ineffectiveness of the current chemical treatments, the RhizoDia project was set up in 2016 to find a viable alternative to these pesticides. The actors involved include the experimental station of La Morinière, the Koppert company, the Agrobiothech Institute (INRA PACA) and the Bourgogne Chamber of Agriculture. The Coccinellidae Rhyzobius lophantae (Blaisdell 1892) was selected as a natural enemy to take part into biological control trials. From 2016 to 2018, trials and measurements were conducted in experimental plots owned by 4 growers, to assess the efficiency of the predation of R.lophantae on P.pentagona. The compiled data reveal that the releases of R.lophantae clean up the infested plots better that the treatments using Chlorpyriphos-methyl. It was also observed that this Coccinellidae is highly mobile, and leaves the plots that don’t host enough preys. Some aspects of its ecology are still to clarify. In 2018, the methods used for this project can’t by applied by the growers, mainly because of the financial cost of the releases. Leads presented in this report will allow to use R.lophantae in an affordable way in a near future, or to launch other (more practical) experimentations.; La culture de cassis en France représente une surface faible (2500 hectares), mais qui alimente toute une filière basée majoritairement sur la transformation. Depuis les années 2000, tous les bassins de production de cassis en France sont infestés par Pseudaulacaspis pentagona (Targioni Tozzetti 1886), une cochenille diaspine très polyphage à la répartition cosmopolite. Son impact sur le cassissier est important, au point de menacer toute la filière. Face à l’inefficacité des traitements chimiques actuels, le projet RhizoDia a été mis en place en 2016, afin de trouver une alternative viable à ces pesticides. Les acteurs impliqués dans ce projet comprennent la station expérimentale de La Morinière, l’Institut Agrobiotech (INRA PACA), le CTIFL, l’entreprise Koppert et la Chambre d’Agriculture de Bourgogne. La Coccinellidae Rhyzobius lophantae (Blaisdell 1892) a été retenue pour être testée en tant qu’auxiliaire dans le cadre d’essais en lutte biologique. De 2016 à 2018, des essais et des mesures ont été réalisés dans les parcelles de 4 producteurs pour mesurer l’efficacité de prédation de R .lophantae sur P. pentagona. Les données cumulées des 3 ans d’expérimentation révèlent que les lâchers de R. lophantae assainissent les parcelles infestées plus efficacement que les traitements utilisant du chlorpyriphos-méthyl. Il a aussi été constaté que cette Coccinellidae est hautement mobile et quitte les parcelles ne présentant pas suffisamment de proies. Certains aspects dont l'écologie restent à éclaircir. En 2018, les méthodes employées pour ce projet ne peuvent directement être appliquées chez les producteurs, principalement à cause du coût financier des lâchers. Des pistes présentées ici permettront d’utiliser R. lophantae de façon abordable dans un futur proche, ou de lancer d’autres expérimentations plus pratiques.

Nectar provisioning by flowering field margins provides food subsidies and contributes to enhance biological control by natural enemies. Sugar resources can improve parasitoids fitness but it is difficult to track their consumption in agricultural fields. We developed a new 13C isotope enrichment method for Centaurea cyanus extra-floral nectar labeling, allowing us to identify, among parasitoids captured at several distances from flowering margins, those which fed with marked nectar. The influence of the distance from flowering margins on insects diversity in crop, on the number of Diaeretiella rapae parasitoids fed with border's nectar, and on Brevicoryne brassicae aphids infestation was investigated in rapeseed production fields. We found no evidence of how flowering field margins can enhance natural pest control but we captured marked parasitoids up to 20 meters in field. Our results show the efficiency and interest of the developed method for insects nectar consumption tracking in agro-ecosystems.; L'implantation en bordure de parcelle de ressources nutritives pour les ennemis naturels, sous la forme de bandes fleuries, présente un grand intérêt pour la lutte biologique contre les ravageurs des cultures. Les ressources sucrées améliorent la fitness des parasitoïdes, mais il est difficile de suivre leur consommation en milieu agricole. Dans cette étude nous avons développé une méthode inédite d'enrichissement isotopique en 13C par Cotton-wick, adapté au marquage du nectar extra-floral du bleuet Centaurea cyanus, afin de pouvoir identifier, parmi les parasitoïdes capturés à différentes distances de la bande fleurie, ceux qui ont consommé du nectar marqué. Nous avons ainsi étudié en parcelles de colza l'influence de la distance aux bandes fleuries sur la diversité des insectes capturés dans la parcelle, sur la proportion de parasitoïdes Diaeretiella rapae ayant consommé du nectar en bordure, et sur l'infestation du puceron Brevicoryne brassicae. Nous n'avons pas pu conclure quant à l'intérêt des bandes fleuries pour le contrôle du ravageur, mais nous avons capturé dans la parcelle des parasitoïde marqués jusqu'à 20 mètres de la bordure. Nos résultats prouvent donc l'efficacité et l'intérêt de la méthode développée pour le suivi de la consommation du nectar par les insectes dans les agro-écosystèmes.