Non-target effects of ten essential oils on the egg parasitoid Trichogramma evanescens

Essential oils (EOs) are increasingly used as biopesticides due to their insecticidal potential. This study addresses their non-target effects on a biological control agent: the egg parasitoid Trichogramma evanescens. In particular, we tested whether EOs affected parasitoid fitness either directly, by decreasing pre-imaginal survival, or indirectly, by disrupting parasitoids' orientation abilities. The effect of Anise, Fennel, Sweet orange, Basil, Coriander, Oregano, Peppermint, Mugwort, Rosemary and Thyme EOs were studied on five strains of T. evanescens. Specific experimental setups were developed, and data obtained from image analysis were interpreted with phenomenological models fitted with Bayesian inference. Results highlight the fumigant toxicity of EOs on parasitoid development. Anise, Fennel, Basil, Coriander, Oregano, Peppermint and Thyme EOs are particularly toxic and drastically reduce the emergence rate of T. evanescens. Most EOs also affect parasitoid behavior: (i) Basil, Coriander, Oregano, Peppermint, Mugwort and Thyme EOs are highly repellent for naive female parasitoids; (ii) Anise and Fennel EOs can have repellent or attractive effects depending on strains; and (iii) Sweet orange, Oregano and Rosemary EOs have no detectable impact on orientation behavior. This study shows that EOs fumigation have non-target effects on egg parasitoids. This highlights the need to cautiously precise the deployment framework of biopesticides in an agroecological perspective

Integrated pest management of Tuta absoluta: practical implementations across different world regions

The South American tomato pinworm, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), has invaded most Afro-Eurasian countries and is threatening worldwide tomato production. Various strategies have been developed and implemented to manage this pest. Here, we present a timely review on the up-to-date development and practical implementation of integrated pest management (IPM) programs for tomato crops across different world regions infested by T. absoluta. While insecticide resistance is a growing concern, biological control via releasing or conserving arthropod natural enemies and sex pheromone-based biotechnical control are the most successful management practices. Agronomic control-related research is an emerging area where the soil fertilization and/or irrigation, as well as breeding of resistant cultivars, has the potential to enhance IPM effectiveness. Grower survey responses in the native areas (i.e., South America), early-invaded areas (i.e., first report between 2006 and 2012) and newly invaded areas (i.e., first report after 2012) showed that the control programs evolved along with the areas and time since invasion. Growers in the early-invaded areas shifted more rapidly from chemical control to biological control compared to those from the native area. In all concerned regions, the pest control failure risk following chemical insecticide applications and the high cost associated with either biological or biotechnical control methods have been the greatest concerns for growers. The information gathered from the native and/or early-invaded areas may help achieve a more effective management in newly invaded areas. Lastly, researchers are expected to break the bottlenecks of some key issues that would enable lowering application cost of novel biorational alternative management options

Renforcer un Collectif interdisciplinaire de réflexion sur l’utilisation des plantes de service pour la REgulation des bioAgresseurs en agriculture : volet animationvolet exploration (ReCREA2)

National audienc

Effet de la limitation en eau sur les émissions de composés organiques volatils chez le chêne vert (Quercus ilex) (approches expérimentale et modélisatrice à différentes échelles spatiales et temporelles)

Les Composés Organiques Volatils Biogéniques (COVB), principalement émis par la végétation et largement représentés par les isoprénoides, influencent la capacité oxydative et le bilan de rayonnement global de la troposphère. Leurs émissions sont diffuses de par l'ampleur des sources (à savoir tous paysages naturels) mais aussi variables car elles sont contro lées par divers facteurs environnementaux, principalement lumière et température. En région méditerranéenne, la disponibilité en eau représente une contrainte environnementale majeure pour les végétaux qui subissent des épisodes de sécheresse sévères et détermine le pattern annuel de l'activité végétale aussi bien que la température ou la lumière. L'objectif de ce travail était de caractériser l'effet d'une limitation en eau sur les émissions biogéniques à différentes échelles temporelles et spatiales chez une espèce modèle Quercus ilex. Grâce à une approche expérimentale, une forte diminution des émissions foliaires a été observée en période de sécheresse, associée à une perturbation du contrôle de la lumière et de la température sur ces émissions. L'extrapolation de cette approche expérimentale à l'aide d'outils de modélisation a permis d'intégrer cet effet à des échelles spatiales plus larges, à savoir canopée et région. On constate alors que si l'effet du stress hydrique n'est pas pris en compte dans les modèles de simulation, ils surestiment les émissions biogéniques lors des périodes de sécheresse. Le modèle de simulation ainsi obtenu à l'échelle régionale est explicite et quantitatif et pourrait être utilisé pour estimer les émissions biogéniques futures dans un contexte de changement globalBiogenic Volatile Organic Compounds (BVOC) are primarily emitted from plants and consist mainly of isoprenoid compounds. They influence the oxidative capacity and the radiative properties of the troposphere. BVOC emissions are diffuse (sources are represented by all natural landscapes), and variable because of the numerous environmental factors, particularly light and temperature that modulate the emission source strength. In Mediterranean regions, water availability represents a major environmental constraint for vegetation, which causes severe drought during summer and determines the annual pattern of the plant activity together with light and temperature. The objective of this thesis was to characterise the effect of water limitations on biogenic emissions at various temporal and spatial scales on the model species Quercus ilex. In an experimental approach, a strong decrease of the foliar emissions was observed during drought events, in association with dissociation of the temperature and light control on the emissions. The up-scaling of the experimental approach with modelling tools allowed to integrate this negative effect at larger spatial scales (namely canopy and region). As a result, emissions were largely overestimated if the water stress effect was not taken into account. The simulation obtained at regional scale is explicit and quantitative, thus could be used to predict biogenic emissions in the on-going global change contextMONTPELLIER-BU Sciences (341722106) / SudocSudocFranceF

Ecotoxicology at the era of biocontrol expansion

Résumé à la destination du public, journalistes et décideurs de l'article "Amichot M, Joly P, Martin-Laurent F, Siaussat D, Lavoir A-V. 2018. Biocontrol, new questions for Ecotoxicology? Environ Sci Pollut Res. 25(34). doi:10.1007/s11356-018-3356-5."Summary of the manuscript "Amichot M, Joly P, Martin-Laurent F, Siaussat D, Lavoir A-V. 2018. Biocontrol, new questions for Ecotoxicology? Environ Sci Pollut Res. 25(34). doi:10.1007/s11356-018-3356-5." for policy makers, journalists

Biocontrol, new questions for Ecotoxicology?

International audienceBiocontrol strategies are viewed as an environment friendly alternative to the use of conventional synthetic pesticides to control pests or weeds in agrosystems and are expected to supersede the use of pesticides. Nevertheless, biocontrol solutions are not devoid of drawbacks. As encountered with conventional pesticides, one can expect side-effects of biopesticides on non-targeted organisms and/or ecosystem processes. The "bio-" prefix in the word "biopesticides" does it necessarily guarantee their environment safe profile? In this context, we call to mind the researchers of the network ECOTOX (French network of ecotoxicology; https://www6.inra.fr/ecotox) in the framework of a roundtable entitled "Biocontrol & Ecotoxicology" on the following questions: who is experienced in ecotoxicology in relation with biocontrol in its own research? To what extend would it be useful to introduce ecotoxicology in biocontrol? What is the fate of biopesticides in the environment? What role could we cast to ecotoxicology in biocontrol regulations? We report here a synthesis of the discussions engaged during the roundtable

Global change-driven modulation of bottom–up forces and cascading effects on biocontrol services

Abiotic and biotic factors affect plants in various ways which in turn affect associated arthropod communities through direct and/or indirect bottom-up interactions. Several review articles have synthesized studies examining the indirect effects of abiotic factors on plant-arthropod interactions, mainly focusing on soil nitrogen, soil water status, and climate change. However, these studies have mostly focused on bitrophic interactions, whereas most ecological systems are composed of at least three trophic levels. Lately, research on plant-mediated multitrophic interactions in plant-arthropod food web has received increasing interest. Both the intensification of agriculture and the global climate change have the potential to trigger bottom-up effects that cascade through trophic links. In this review article, we synthesize the most recent studies describing how abiotic changes could modulate plant-mediated bottom-up forces and how it could affect arthropod communities and associated biocontrol services. We discuss potential for increasing the sustainability of managed and natural ecosystems, and highlight road maps for future studies

Effects of abiotic factors on HIPV-Mediated interactions between plants and parasitoids

In contrast to constitutively emitted plant volatiles (PV), herbivore-induced plant volatiles (HIPV) are specifically emitted by plants when afflicted with herbivores. HIPV can be perceived by parasitoids and predators which parasitize or prey on the respective herbivores, including parasitic hymenoptera. HIPV act as signals and facilitate host/prey detection. They comprise a blend of compounds: main constituents are terpenoids and "green leaf volatiles." Constitutive emission of PV is well known to be influenced by abiotic factors like temperature, light intensity, water, and nutrient availability. HIPV share biosynthetic pathways with constitutively emitted PV and might therefore likewise be affected by abiotic conditions. However, the effects of abiotic factors on HIPV-mediated biotic interactions have received only limited attention to date. HIPV being influenced by the plant's growing conditions could have major implications for pest management. Quantitative and qualitative changes in HIPV blends may improve or impair biocontrol. Enhanced emission of HIPV may attract a larger number of natural enemies. Reduced emission rates or altered compositions, however, may render blends imperceptible to parasitoides and predators. Predicting the outcome of these changes is highly important for food production and for ecosystems affected by global climate change

Do photosynthetic limitations of evergreen <em>Quercus ilex</em> leaves change with long-term increased drought severity?

a indexerInternational audienceSeasonal drought can severely impact leaf photosynthetic capacity. This is particularly important for Mediterranean forests, where precipitation is expected to decrease as a consequence of climate change. Impacts of increased drought on the photosynthetic capacity of the evergreen Quercus ilex were studied for two years in a mature forest submitted to long-term throughfall exclusion. Gas exchange and chlorophyll fluorescence were measured on two successive leaf cohorts in a control and a dry plot. Exclusion significantly reduced leaf water potential in the dry treatment. In both treatments, light-saturated net assimilation rate (Amax), stomatal conductance (gs), maximum carboxylation rate (Vcmax), maximum rate of electron transport (Jmax), mesophyll conductance to CO2 (gm) and nitrogen investment in photosynthesis decreased markedly with soil water limitation during summer. The relationships between leaf photosynthetic parameters and leaf water potential remained identical in the two treatments. Leaf and canopy acclimation to progressive, long-term drought occurred through changes in leaf area index, leaf mass per area and leaf chemical composition, but not through modifications of physiological parameter