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Steinernema carpocapsaeis an entomopathogenic nematode (EPN) used in biological control of agricultural pest insects. It enters the hemocoel of its host via the intestinal tract and releases its symbiotic bacteriumXenorhabdus nematophila, which kills the insect in less than 48 hours. Although several aspects of its interactions with insects have been extensively studied, still little is known about the immune and physiological responses of its different hosts. In order to improve this knowledge, we examined the transcriptional responses to EPN infestation of the fat body, the hemocytes and the midgut in the lepidopteran pest modelSpodoptera frugiperda(Lepidoptera: Noctuidae).Our results indicate that the tissues poorly respond to the infestation at an early time post-infestation of 8 h, even though the proliferation of the bacterial symbiont within the hemocoel is detected. Only 5 genes are differentially expressed in the fat body of the caterpillars. However, strong transcriptional responses are observed at a later time point of 15 h post-infestation in all three tissues. While few genes are differentially expressed in the midgut, tissue-specific panels of induced metalloprotease inhibitors, immune receptors and antimicrobial peptides together with several uncharacterized genes are up-regulated in the fat body and the hemocytes. In addition, among the most up-regulated genes, we identified new potential immune effectors, unique to Lepidoptera, for which we present evidence of acquisition by Horizontal Gene Transfer from bacteria.Altogether, these results pave the way for further functional studies of the mobilized genes’ involvement in the interaction with the EPN.Author summaryThe Fall Armyworm,Spodoptera frugiperda, is a major agricultural pest. The caterpillars cause extensive damage to crops of importance such as corn, rice, sorghum and cotton. Originally from the Americas, it is currently becoming invasive in other parts of the world, first in Africa in 2016, then in India and now in south-east Asia. Programs of biological control against insect pests are increasingly encouraged around the world and include the use of pathogens. Entomopathogenic nematodes such asSteinernema carpocapsaeare already commercialized as organic pesticides. These nematodes live in the soil and enter the body of their insect preys. Once within the insects, they release their symbiotic bacteria (Xenorhabdus nematophilain this case), which infect and kill the host in a few hours. The nematodes can then feed on the dead insects, reproduce and resume their life cycle. It is a major challenge to understand how EPN achieve their pathogenicity as well as how the insects can resist them. Here we provide the foundation for such an interaction between EPN and a Lepidoptera. We analyzed the dynamic of transcriptional response in three insect tissues (midgut, fat body and hemocytes) upon infestation by EPN. Not many studies have been performed genome-wide on such an interaction, and none on a Lepidopteran model of economical importance. Our transcriptomic approach revealed some specificities of the Lepidopteran defense mechanisms. In particular, we discovered a set of genes, acquired in Lepidoptera from bacteria by Horizontal Gene Transfer, that probably encode proteins with antibiotic activity.

Significance Certain adapted insect herbivores utilize plant toxins for self-defense against their own enemies. These adaptations structure ecosystems and limit our capacity to use biological control agents to manage specialized agricultural pests. We show that entomopathogenic nematodes that are exposed to the western corn rootworm, an important agricultural pest that sequesters defense metabolites from maize, can evolve resistance to these defenses. Resisting the plant defense metabolites likely allows the nematodes to infect and kill the western corn rootworm more efficiently. These findings illustrate how predators can counter the plant-based resistance strategies of specialized insect herbivores. Breeding or engineering biological control agents that resist plant defense metabolites may improve their capacity to kill important agricultural pests such as the western corn rootworm., Plants defend themselves against herbivores through the production of toxic and deterrent metabolites. Adapted herbivores can tolerate and sometimes sequester these metabolites, allowing them to feed on defended plants and become toxic to their own enemies. Can herbivore natural enemies overcome sequestered plant defense metabolites to prey on adapted herbivores? To address this question, we studied how entomopathogenic nematodes cope with benzoxazinoid defense metabolites that are produced by grasses and sequestered by a specialist maize herbivore, the western corn rootworm. We find that nematodes from US maize fields in regions in which the western corn rootworm was present over the last 50 y are behaviorally and metabolically resistant to sequestered benzoxazinoids and more infective toward the western corn rootworm than nematodes from other parts of the world. Exposure of a benzoxazinoid-susceptible nematode strain to the western corn rootworm for 5 generations results in higher behavioral and metabolic resistance and benzoxazinoid-dependent infectivity toward the western corn rootworm. Thus, herbivores that are exposed to a plant defense sequestering herbivore can evolve both behavioral and metabolic resistance to plant defense metabolites, and these traits are associated with higher infectivity toward a defense sequestering herbivore. We conclude that plant defense metabolites that are transferred through adapted herbivores may result in the evolution of resistance in herbivore natural enemies. Our study also identifies plant defense resistance as a potential target for the improvement of biological control agents.

Steinernema carpocapsae is an entomopathogenic nematode (EPN) used in biological control of agricultural pest insects. It enters the hemocoel of its host via the intestinal tract and releases its symbiotic bacterium Xenorhabdus nematophila. In order to improve our knowledge about the physiological responses of its different hosts, we examined the transcriptional responses to EPN infestation of the fat body, the hemocytes and the midgut in the lepidopteran pest Spodoptera frugiperda. The tissues poorly respond to the infestation at an early time post-infestation of 8 h with only 5 genes differentially expressed in the fat body of the caterpillars. Strong transcriptional responses are observed at a later time point of 15 h post-infestation in all three tissues. Few genes are differentially expressed in the midgut but tissue-specific panels of induced metalloprotease inhibitors, immune receptors and antimicrobial peptides together with several uncharacterized genes are up-regulated in the fat body and the hemocytes. Among the most up-regulated genes, we identified new potential immune effectors, unique to Lepidoptera, which show homology with bacterial genes of unknown function. Altogether, these results pave the way for further functional studies of the responsive genes' involvement in the interaction with the EPN.

Evaluation des nématodes entomopathogènes et leurs bactéries symbiotiques pour lutter contre les taupins. Natural Products and Biocontrol et Journée Elicitra

La collection de Nématodes Entomopathogènes : Ressources biologiques utilisables comme agents de Bio-contrôle. 3. International Congress Natural Products and Biocontrol

A new formulation of EntomoPathogenic Nematodes (EPNs) vectorization of biological control agents . Réunion du Consortium Biocontrôle

Texte intégral accessible uniquement aux membres de l'Université de Lorraine; The developpement and use of alternative methods in biological contol is an expanding field. The use of nematodes, particularly entomopathogenic nematodes against pests insects, is one of them and is the topic of this report. A culture medium was used and optimized for the multiplication of Steinernema carpocapsae. The scale-up was also tested. An egg-based medium was validated for Steinernema carpocapsae, with a multiplication means rate of 400 and as effective as a commercial nematode strain. On the other hand, the scale-up did not succeed and no multiplication of nematode could be observed in a larger volume.; La mise au point et l'utilisation de méthodes alternatives en lutte biologique est un domaine en pleine expansion. L'utilisation de nématodes, en particulier de nématodes entomopathogènes contre les insectes ravageurs, est l'une d'entre elles et fait le sujet de ce rapport. Un milieu de culture a été utilisé et optimisé pour la multiplication de Steinernema carpocapsae. L'augmentation de l'échelle de culture a également été testé. Un milieu à base d’oeuf a été validé pour Steinernema carpocapsae, avec un taux de multiplication moyen de 400 et aussi efficace qu'une souche de nématode commerciale. En revanche, l'augmentation d'échelle n'a pas pu aboutir et aucune multiplication de nématode n'a pu être observée.

De nombreuses cultures subissent chaque année des attaques de larves de taupins qui occasionnent des pertes de rendement ou une dégradation de la qualité des produits. La protection des cultures est réalisée préventivement grâce à l’application de produits phytopharmaceutiques. En absence de références récentes concernant la répartition des principales espèces présentes en France et le manque de connaissance concernant leur biologie, il n’est pas possible de prévoir les risques d’attaques de taupins. Plus de 700 enquêtes parcellaires ont été réalisées dans le but de cartographier les espèces de taupins puis d’identifier et hiérarchiser les facteurs susceptibles d’influencer l’abondance de larves de taupins et l’intensité des attaques occasionnées aux plantes cultivées. L’analyse des données a été réalisée sur des parcelles de maïs. Les caractéristiques de sol (pH, taux de matière organique, texture du sol) et la pluviométrie estivale sont des facteurs qui influencent l’abondance de larves de taupins dans le sol. Les conditions météorologiques subies avant et après le semis, le type de rotation – avec notamment la présence d’une prairie dans la parcelle ou dans son environnement proche – sont des facteurs qui modifient le risque d’attaques sur la culture. Ces enseignements permettent d’appréhender les risques mais il demeure difficile de caractériser un risque à l’échelle de la parcelle avec précision. En parallèle, des expérimentations réalisées au champ ont permis d’évaluer l’intérêt de champignons entomopathogènes Metarhizium anisopliae pour la protection de différentes cultures. D’autres essais ont démontré l’efficacité de glucosinolates avec une diminution des attaques de taupins de l’ordre de 50%. Des travaux en conditions contrôlées ont également mis en évidence la pertinence de stratégies innovantes basées sur l’usage de macroorganismes (nématodes entomopathogènes) ou de semiochimiques., Many crops are annually attacked by wireworms which cause yield losses or degradation of product quality. Crop protection is carried out preventively through the application of plant protection products. In the absence of recent references concerning the distribution of the main species present in France and the lack of knowledge concerning their biology, it is not possible to predict the risks of attacks by wireworms. Over 700 fields were investigated in order to map wireworm species in France and to identify the main factors involved in the abundance of wireworms and intensity of damage on crops. Data analysis was carried out on maize fields. Soil characteristics (pH, organic matter content, soil texture) and the summer rainfall are factors that influence abundance of wireworms in the soil. Weather conditions encountered before and after planting, rotation type - including the presence of a meadow in the plot or in its immediate environment - are factors that influence the level of damage on maize. These knowledges allow comprehend the risks, but it remains difficult to characterize it precisely for each field. Experiments led in the fields have assessed the pathogenic fungus Metarhizium anisopliae interest for the protection of several crops. Other trials demonstrated effectiveness of glucosinolates provoking a 50% reduction of wireworms attack. Works under controlled conditions highlighted relevance of innovative strategies using macroorganisms (entomopathogenic nematode) or semiochemicals.

Entomopathogenic nematodes (EPNs) are parasites of soil-dwelling insects that occur in natural and agricultural soils around the world. The current study focuses on the unexplored coastal zone of Lebanon where soil samples were taken in different sites chosen randomly along the coast like beaches, agricultural and herbaceous fields. In total, 350 soil samples were collected, mainly from the southern part of the country. An integrated approach, combining both traditional (morphological) and molecular methods, was used to characterize entomopathogenic nematode species encountered. Two named-species are added to the EPNs catalog in Lebanon from 4 samples out of the total 350 samples isolated: Heterorhabditis indica , reported for the first time in the country (samples AYAB6 and BRA20) and Steinernema feltiae (samples ANFA5 and EDA1). Furthermore, one undescribed potential entomopathogenic nematode belonging to Oscheius genus was recovered. The symbiotic bacteria from S . feltiae and H . indica were also molecularly identified through the use of five gene fragments recA , gyrB , dnaN , gltX and infB . Phylogenetic relationships of entomopathogenic nematodes and their symbiotic bacteria were inferred by using maximum-likelihood analysis. Soil studies were subsequently carried out in order to assess a possible relationship between soil parameters and their effects on EPNs. Results indicate that sandy texture and moisture are key factors for the presence and survival of EPNs in the soil in Lebanon.

Xenorhabdus is a bacterial symbiont of entomopathogenic Steinernema nematodes and is pathogenic for insects. Its life cycle involves a stage inside the insect cadaver, in which it competes for environmental resources with microorganisms from soil and the insect gut. Xenorhabdus is, thus, a useful model for identifying new interbacterial competition systems. For the first time, in an entomopathogenic bacterium, Xenorhabdus doucetiae strain FRM16, we identified a cdi-like locus. The cdi loci encode contact-dependent inhibition (CDI) systems composed of proteins from the two-partner secretion (TPS) family. CdiB is the outer membrane protein and CdiA is the toxic exoprotein. An immunity protein, CdiI, protects bacteria against inhibition. We describe here the growth inhibition effect of the toxic C-terminus of CdiA from X. doucetiae FRM16, CdiA-CTFRM16, following its production in closely and distantly related enterobacterial species. CdiA-CTFRM16 displayed Mg2+-dependent DNase activity, in vitro. CdiA-CT (FRM16)-mediated growth inhibition was specifically neutralized by CdiI(FRM16). Moreover, the cdi(FRM16) locus encodes an ortholog of toxin-activating proteins C that we named CdiC(FRM16). In addition to E. coli, the cdiBCAI-type locus was found to be widespread in environmental bacteria interacting with insects, plants, rhizospheres and soils. Phylogenetic tree comparisons for CdiB, CdiA and CdiC suggested that the genes encoding these proteins had co-evolved. By contrast, the considerable variability of CdiI protein sequences suggests that the cdiI gene is an independent evolutionary unit. These findings further characterize the sparsely described cdiBCAI-type locus.

Presence of entomopathogenic nematodes along the coastal area in Lebanon. 21. Conférence Scientifique Internationale du LAAS

A new species of entomopathogenic nematode (EPN), Steinernema tbilisiensis sp. n. is described. The species was isolated from soil samples of the deciduous forest located in the Tbilisi area. Morphological and morphometric data as well as phylogenetic analysis show that S. tbilisiensis sp. n. belongs to the group S. affine/intermedium. S. tbilisiensis sp. n. has been attributed to the group S. affine/intermedium on the basis of spicule and gubernaculum structure. The new species differs from other species of S. affine/intermedium group in the following diagnostic characters: the spicule of S. tbilisiensis sp. n. is the smallest and the gubernaculum of S. tbilisiensis sp. n. is shorter than other species of the S. affine/intermedium group. Infective juveniles (IJs) of S. tbilisiensis sp. n. are distinguished by a relatively long body (L = 866 µm), the position of excretory pore (EP = 72 µm), the length of the esophagus (ES = 140 µm) and the length of the anal body width (ABW = 25 µm). IJs of S. tbilisiensis sp. n. have four lateral lines like S. beddingi, but the number of lines is six in S. affine, S. sichuanense and S. intermedium. Also the analysis of rDNA (28S and ITS) gene sequences depicts this Steinernema species as a distinct and unique entity. The symbiotic bacteria of S. tbilisiensis sp. n. was isolated and found to be Xenorhabdus bovienii using a multigene approach.

The bacterial symbionts SF41T and SF783 were isolated from populations of the insect pathogenic nematode Heterorhabditis zealandica collected in South Africa. Both strains were closely related to strain Q614 isolated from a population of Heterorhabditis sp. collected from soil in Australia in the 1980s. Sequence analysis based on a multigene approach, DNA–DNA hybridization data and phenotypic traits showed that strains SF41T, SF783 and Q614 belong to the same species of the genus Photorhabdus with Photorhabdus temperata subsp. cinerea as the most closely related taxon (DNA–DNA hybridization value of 68 %). Moreover, the phylogenetic position of Photorhabdus temperata subsp. cinerea DSM 19724T initially determined using the gyrB sequences, was reconsidered in the light of the data obtained by our multigene approach and DNA–DNA hybridization experiments. Strains SF41T, SF783 and Q614 represent a novel species of the genus Photorhabdus , for which the name Photorhabdus heterorhabditis sp. nov. is proposed (type strain SF41T = ATCC BAA-2479T = DSM 25263T).

Les nématodes des genres Heterorhabditis et Steinernema sont des pathogènes d’insectes vivants dans les sols et sont commercialisés comme bio-insecticides pour lutter contre certains ravageurs de culture. Les stades infestants (IJs) vivent à l’état libre dans le sol et transportent en symbiose dans leur tube digestif des entérobactéries des genres Xenorhabdus et Photorhabdus qui seront ensuite libérées dans les insectes parasités. Il s’agit d’associations très spécifiques, puisque chaque espèce de nématode est généralement associée à une espèce unique de bactéries. Les bactéries symbiotiques sont capables de secréter un très grand nombre de toxines insecticides, de molécules permettant de neutraliser les défenses de l’insecte, de molécules antibiotiques et d’enzymes de dégradation. Les nématodes utilisent ainsi leurs symbiontes bactériens comme armes pour tuer l’insecte, pour éliminer les autres micro-organismes sensibles à leurs antimicrobiens et convertir la dépouille en sources nutritives qui leur permettront de se développer et de se multiplier. Lorsque les ressources sont épuisées, les nématodes se réassocient à leurs bactéries et quittent la dépouille de l’insecte à la recherche de nouvelles proies. Si le cycle biologique des nématodes et le rôle joué par les symbiontes lors du processus infectieux sont bien documentés, peu de choses sont connues sur l’écosystème microbien transporté par les larves infestantes du nématode. Il a été montré que des bactéries appartenant à des genres très variés (Acinetobacter, Ochrobactrum, Paenibacillus, Pseudomonas, Alcaligenes, etc…) étaient régulièrement associées à des nématodes entomopathogènes (1, 2). Nous nous intéressons au rôle de ce microbiome dans le processus infectieux du couple bactério-helminthique, en combinant des approches de comparaison génomique in silico et des approches de métagénomiques descriptives et fonctionnelles. L’analyse de génomique comparative met en évidence que les bactéries Xenorhabdus et Photorhabdus peuvent partager de nombreux gènes de leur génome accessoire avec des bactéries de l’environnement (sol et plantes), ce qui suggère des transferts génétiques horizontaux fréquents dans une niche écologique d’espace restreint (nématode ou cadavre de l’insecte). Les premiers résultats obtenus en PCR-TTGE ciblant l’ADNr 16S révèle la présence d’un cortège bactérien inter-cuticulaire stable chez certains nématodes. Ces données préliminaires nous permettront d’engager un programme de séquençage à haut débit afin d’identifier en profondeur ce microbiome. A moyen terme, ce projet devrait nous permettre de caractériser le pathobiome des nématodes entomopathogènes et mieux caractériser le rôle de l’holobionte (macroorganisme et son cortège de microorganismes) dans le processus infectieux des nématodes entomopathogènes. (1) Gouge DH & Snyder JL (2006). Temporal association of entomopathogenic nematodes (Rhabditida: Steinernematidae and Heterorhabditidae) and bacteria. J. Invertebrate Pathology 91: 147–157. (2) Babic I, Fischer-Le Saux M, Giraud E, Boemare N (2000). Occurrence of natural dixenic associations between the symbiont Photorhabdus luminescens and bacteria related to Ochrobactrum spp. in tropical entomopathogenic Heterorhabditis spp. (Nematoda, Rhabditida). Microbiology 146:709–718.

Après plus de trois ans de travaux de recherche, le programme PETAAL, coordonné par le centre technique national Plante & Cité et porté par la société Koppert livre ses résultats : il propose une stratégie combinant l'utilisation de deux auxiliaires pour réguler les populations de tigre du platane.

Après plus de trois ans de travaux de recherche, le programme PETAAL, coordonné par le centre technique national Plante & Cité et porté par la société Koppert livre ses résultats : il propose une stratégie combinant l'utilisation de deux auxiliaires pour réguler les populations de tigre du platane.

National audience; La seule lutte biologique efficace recommandée pour contrôler les charançons est l'application de nématodes entomopathogènes. L'objectif de notre étude menée en Guadeloupe a été de tester l'efficacité au champ et dans nos conditions pédoclimatiques une souche de nématodes. La pression du charançon des agrumes s'est avérée très forte sur nos parcelles expérimentales. L'efficacité du nématode pour les réguler a été démontrée. Il est donc recommandé d'appliquer les nématodes à la plantation (début de la saison des pluies) et de ré-inoculer trois mois après(toujours en saison humide). Même si ce moyen de lutte semble efficace, d'autres méthodes de contrôle de ce ravageur doivent être mises en œuvre simultanément.

La lutte intégrée est une méthode de lutte contre les ennemis du verger intégrant la lutte biologique et la lutte chimique. L'utilisation de produits phytosanitaires intervient en ultime recours, après avoir utilisé tous les moyens naturels de lutte et surtout lorsque l'attaque parasitaire a dépassé un seuil tolérance préalablement défini (ce seuil dépend du parasite, de l'écologie et du niveau de dégâts accepté par le producteur). Les produits phytosanitaires utilisés sont sélectionnés vis à vis de leur impact sur l'environnement et sur la faune auxiliaire. Après une formation, un groupe d'agriculteurs accompagnés par les agents du CIRAD devaient valider l'utilisation d'une fiche de comptage des insectes, un outil essentiel de la lutte raisonnée dans les vergers. Simple et pratique, elle mobilise l'utilisateur environ 1 heure tous les 15 jours. Cependant, malgré la coopération de la plupart des agriculteurs, la profession, dans sa globalité, semble peu disposée à utiliser cette fiche malgré, paradoxalement, des demandes récurrentes d'accompagnement technique. Cependant, si l'utilisation de cette fiche, validée en 2007, n'a pas été systématique, les agriculteurs formés à ce mode de production ont appris à mieux observer les maladies et ravageurs et à mieux raisonner la protection phytosanitaire de leur verger. L'intégration de ces principes de lutte intégrée permet également de lutter contre un ravageur majeur des jeunes plantations d'agrumes en Guadeloupe, le 'Jackot' (Diaprepes spp.). En effet, ses ennemis naturels sont ainsi mieux protégés, cependant et compte tenu de l'importance des dégâts encore observés ces dernières années, le Cirad et Inra ont décidé de compléter cette régulation naturelle par un programme de lutte biologique via l'utilisation de nématodes entomopathogènes (type Heterorhabditis). De 2005 à 2006, les bases de ce projet ont été mises en place: élevage de l'hôte Galleria mellonella, amplification de la souche de nématodes, acquisition de connaissances et d'expérience. De 2006 à 2007, la diffusion des nématodes a été entreprise auprès des agriculteurs et des pépiniéristes (plus de 4600 plants inoculés en 2006). La diffusion chez le producteur se fait après identification de la parcelle (jeunes plantations prioritaires, caractéristiques physico-chimiques du sol, non-utilisation de pesticides, possibilité d'irrigation...), si toutes ces conditions d'acclimatation sont réunies, les nématodes entomopathogène sont inoculés au sol (au pied des arbres), via son hôte privilégié, Galleria mellonella. Ce moyen de diffusion est plus coûteux en temps et en matériel, mais semble efficace. Ainsi, plus de 3800 jeunes plants d'agrumes ont été protégés grâce à ce principe de juin 2006 à juillet 2007, représentant environ une quinzaine d'hectares (principalement en Côte sous le vent et en Nord Basse-Terre). Même si cette méthode de diffusion est fastidieuse, l'agriculteur constate avec satisfaction que les pertes liées à ce ravageur semblent diminuées voire stoppées. Parallèlement à cette diffusion auprès de la profession, différentes expérimentations visant à mesurer l'efficacité de cette lutte biologique sont menées sur la station expérimentale du Cirad Vieux-Habitants. Des tests de survie des nématodes sont par exemple réalisés régulièrement sur une parcelle d'agrumes ce qui a permis d'observer leur survie en plein champ pendant au moins 3 mois. De même, un suivi des populations de Diaprepes est également mené grâce à des pièges d'émergence et des pondoirs, l'essai devrait prendre fin en décembre 2007 puisque les arbres témoins (non inoculé en nématodes entomopathogènes) sont très affaibli contrairement à ceux inoculés. La lutte biologique contre Diaprepes doit être envisagée sur du long terme. La diffusion des nématodes est un travail de fond qui prendra encore quelques années. Plus tôt les vergers seront inoculés par ces nématodes, plus tôt ceux-ci agiront et augmenteront les chances de survie des jeunes arbres. Cette

The major groups of entomopathogens that include taxa with pathogenicity to Plutella xylostella are discussed. Among the viruses, several of the Autographa californica MNPV related viruses with wide host ranges, exhibit variable virulence to P. xylostella larvae. At least two of these viruses have been marketed for control of a range of pests including P. xylostella. The recently isolated PxMNPV, also related to AcalMNPV, is very significantly more virulent to P. xylostella than others in the same family. The highly specific P. xylostella granulovirus, previously dismissed because of its environmental sensitivity, is being evaluated in E. Africa where market forces are encouraging biopesticide use on export crops destined for the EU. Of the fungal Hyphomycete species infective to P. xylostella, the commercial product Mycotrol® based on Beauveria bassiana strain GHA has been shown to be effective in the field and the Entomophthoralean species Zoophthora radicans shows promise when used in autodissemination traps, despite problems of persistence. Bacillus thuringiensis continues to be the dominant pathogen used inundatively against P. xylostella, with most commercial products based on the Bt kurstaki subspecies, although Bt aizawai has been used where resistance to Bt kurstaki exists. Entomopathogenic nematodes in the genera Steinernema and Heterorhabditis penetrate all P. xylostella instars, as well as pupae and adults although there is variation in the efficacy of different isolates. Their field use is limited by abiotic factors but spraying at dusk and the use of UV protectants and desiccation protective formulations improves efficacy. Vairimorpha imperfecta is a highly virulent microsporidian pathogen of P. xylostella with potential as a biocontrol agent. However, it also leads to deficiencies in offspring of Trichogramma chilonis that parasitize infected larvae. While several pathogens infective to P. xylostelle now are under commercial development, Bt constitutes the most significant control option. In common with most entomopathogens destined for inundative field application, development of suitable formulation and dissemination technologies remains an over-riding priority if the other pathogens are to gain a market share.

The black weevil #Cosmopolites sordidus# (Germar) 1824 is one of the major pest of bananas. In French West Indies banana plantations, control of this pest is often based on insecticide applications. Therefore, considering the biology of the weevil, the use of entomopathogenic nematodes may give good results. In Guadeloupe and Martinique, researches have been led since more than 10 years to set up biological control methods. In a first step, different strains of entomopathogenic nematodes have been selected for their pathogenicity. Moreover, their survival ability in banana fields has been evaluated. These preliminary works have allowed the identification of two strains of #Steinernema# spp. as good candidate for #C. sordidus# control. On one hand, first field application tests used pulverization of nematodes suspension around pseudo-stems. But black weevils population declines were insufficient compared to results obtained with insecticides. On the other hand, mass-trapping using pheromone lure have given good field results, excepted when the #C. sordidus# population levels were very high. Pheromone traps may also be use to contaminate weevils with entomopathogenic nematodes instead of killing them. We are evaluating the interest of pheromone traps using pheromone lure on which we replaced each week 5 #Galleria mellonella# larvae previously inoculated with #Steinernema carpocapsae# (Weiser). Very promising results were obtained after 18-months study, with a better weevil than observed with two insecticide applications per year. (Texte intégral)

International audience; Cosmopolites sordidus (Germar, 1824) is one of the major pest of bananas in the Caribbean. Several techniques can be applied to avoid use of insecticides. On one hand, laboratory studies have shown that some specific strains of Steinermema spp. could contribute efficiently to the control of this pest. Unfortunately, field applications of formulations of S. carpocapsae often give inconsistent results due to formulation and conservation constraints. On the other hand, mass-trapping using pheromone lure has given good field results, excepted when the C. sordidus population levels were very high. ln this study, we used pheromone traps to contaminate weevils with entomopathogenic nematodes instead of killing them. During a 10 month study, we evaluated the interest of pheromone traps using pheromone lure on which we replaced each week new Galleria mellonella larvae previously inoculated with S. carpocapsae (Weiser). ln this experiment, promising results were obtained with a reduction of attacked plants from 98.5 to 40% and a reduction of the attack severity (according to Vilardebo's coefficient) from 42 to 23.

Facultatively sexual entomopathogenic nematodes are a promising model for the experimental study of the adaptive values of sex. Our experiments in the laboratory showed that entomopathogenic nematodes display at least two different strategies in regulating the degree of amphimix as a response to nutritional stress. One strategy promotes the production of males, amphimix and the genetic variability of the offspring, improving the chances for a successful new adaptation. Another strategy increases the production of hermaphrodites at the expense of males, increasing the total number of reproductive individuals and thus the total number of offspring produced. Surprisingly, the strategy used depends upon the strain of symbiotic bacteria the nematodes are growing. The relevance of the results, in helping to discriminate between rival theories for the evolutionary maintenance of sex, is discussed.

Naturally occurring entomopathogens are important regulatory factors in insect populations. Many species are employed as biological control agents of insect pests in row and glasshouse crops, orchards, ornamentals, range, turf and lawn, stored products, and forestry and for abatement of pest and vector insects of veterinary and medical importance. The comparison of entomopathogens with conventional chemical pesticides is usually solely from the perspective of their efficacy and cost. In addition to efficacy, the advantages of use of microbial control agents are numerous. These include safety for humans and other nontarget organisms, reduction of pesticide residues in food, preservation of other natural enemies, and increased biodiversity in managed ecosystems. As with predators and parasitoids, there are three basic approaches for use of entomopathogens as microbial control agents: classical biological control, augmentation, and conservation. The use of a virus (Oryctes nonoccluded virus), a fungus (Entomophaga maimaiga), and a nematode (Deladenus siricidicola )a s innoculatively applied biological control agents for the long-term suppression of palm rhinoceros beetle (Oryctes rhinoceros), gypsy moth (Lymantria dispar), and woodwasp (Sirex noctilio), respectively, has been successful. Most examples of microbial control involve inundative application of entomopathogens. The most widely used microbial control agent is the bacterium Bacillus thuringiensis. The discovery of new varieties with activity against Lepidoptera, Coleoptera, and Diptera and their genetic improvement has enhanced the utility of this species. Recent developments in its molecular biology, mode of action, and resistance management are reviewed. Examples of the use, benefits, and limitations of entomopathogenic viruses, bacteria, fungi, nematodes, and protozoa as inundatively applied microbial control agents are presented. Microbial control agents can be effective and serve as alternatives to broad-spectrum chemical insecticides. However, their increased utilization will require (1) increased pathogen virulence and speed of kill; (2) improved pathogen performance under challenging environmental conditions (cool weather, dry conditions, etc.); (3) greater efficiency in their production; (4) improvements in formulation that enable ease of application, increased environmental persistence, and longer shelf life; (5) better understanding of how they will fit into integrated systems and their interaction with the environment and other integrated pest management (IPM) components; (6) greater appreciation of their environmental advantages; and (7) acceptance by growers and the general public. We envision a broader appreciation for the attributes of entomopathogens in the near to distant future and expect to see synergistic combinations of microbial control agents with other technologies. However, if future development is only market driven, there will be considerable delays in the implementation of several microbial control agents that have excellent potential for use in IPM programs.

Entomopathogenous nematodes are well known biocontrol agents of insects. They live in the superficial layer of the soil, a location where ticks accomplish their molt and where they oviposit their eggs, making them, theoretically, the preys of infective larvae of nematodes. Seventeen strains of entomopathogenous nematodes: eight strains of Steinernema and nine strains of Heterorhabditis were placed in contact with each of the free living stages of three tick species: Amblyomma variegatum, Boophilus microplus and B. annulatus. The first two species were resistant to all the nematode strains that were tested, whereas B. annulatus was susceptible to all of them. Ovipositing females were more susceptible than females during the preoviposition period. There were no anatomical differences between the two species of Boophilus which can account for such differences in their susceptibility. The use of nematodes to control some species of ticks should be considered.

Il existe 2 espèces de termites nuisibles sur le palmier à huile en Indonésie : Coptotermes curvignathus Holmgren (Rhinotermitidae) qui attaque les tissus et qui, éventuellement, tue l'arbre et Macrotermes gilvus (Hagen) (Termitidae) qui désorganise le système racinaire, ce qui peut quelques fois causer la chute de l'arbre. Elles représentent une menace sérieuse dans les replantations récentes et particulièrement sur les sols tourbeux à Sumatra. Dans cette communication, on a étudié le comportement de ces termites et les dégats dont elles sont responsables. Plusieurs méthodes de lutte, telles que lutte mécanique, lutte chimique et traitements biologiques ont été tentées et les résultats ont été présentés

Modalités utilisables dans le cadre de l'établissement d'une lutte intégrée contre Cosmopolites sordidus. Prophylaxie, lutte culturale, estimation de l'infestation, utilisation de pièges toxiques, lutte chimique, décision d'une application de pesticides, lutte biologique employant des prédateurs, des champignons entomopathogènes et des nématodes entomoparasites; lutte, tolérance et résistance variétales.

L'agressivité des nématodes parasites d'insectes Heterorhabditidae et Steinernematidae envers les jeunes tétards du crapaud Bufo marinus diffère avec la souche. L'adulte du lézard iguanide Anolis marmoratus est également sensible à certaines souches. La grenouille Eleutherodactylus sp. adulte n'est pas sensible. Les bactéries Xenorhabdus spp inoculées massivement, par scarification du derme, à la souris blanche (Mus musculus) n'ont déclenché aucune dermatose.

La lutte chimique contre les charançons du bananier (Cosmopolites sordidus, Metamasius sp. et Temnoschoita sp.) n'étant pas toujours possible, on examine l'intérêt de pratiques culturales (association avec caféiers), de la lutte biologique (prédateurs, champignons entomopathogènes, etc.). L'étude du comportement, le mécanisme de l'attraction sont évoqués, ainsi que les différences de sensibilités variétales

Les nématodes entomopathogènes (NEPs). Réunion de lancement - EMBA

Background: The infective juveniles (free form) of the nematodes Steinernema are in closed symbiotic association with the intestinal bacteria Xenorhabdus (Enterobacteriaceae). The couple Steinernema – Xenorhabdus represents an effective insecticidal complex against a wide range of insect pests. The Steinernema carpocapsae – Xenorhabdus nematophila couple was the most studied. The bacterial symbiont X. nematophila is an entomopathogenic bacterium since it kills several lepidopteran insects after injection without its nematode host. By contrast, other Xenorhabdus species belonging to other Steinernema – Xenorhabdus couples have recently been identified as non-virulent against lepidopteran insects.Objectives: The existence of non-virulent Xenorhabdus symbiont led us to search for an auxiliary microbiota that could participate to the Steinernema – Xenorhabdus infectivity in the insect. Methods: The auxiliary bacterial microbiota of five Steinernema – Xenorhabdus couples was isolated by classical culture techniques after crushing of infective juveniles. This microbiota was compared with the one isolated in lepidopteran model insects infested by the same Steinernema – Xenorhabdus couples. Biochemical (API tests) and molecular (sequencing of the 16S rRNA gene) characterization were undergone to identify the OTUs. Antimicrobial activities against Xenorhabdus strains and pathology assays by direct injection into larvae of Spodoptera littoralis were conducted for identified taxon.Conclusion: We identified up to seven cultivable colonial morphotypes associated with each of the five Steinernema – Xenorhabdus couples. The matching OTUs belong to the genera Delftia, Providencia, Acinetobacter, Serratia, Stenotrophomonas, Ochrobactrum and Pseudomonas depending on the Steinernema – Xenorhabdus couples. Some of them were also identified in insect cadavers after Steinernema – Xenorhabdus infestation and displayed antimicrobial and virulence properties. Altogether, these data suggest that other bacterial taxons than Xenorhabdus could participate to the infectious process in insect.