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Conservation biological control aims to enhance populations of natural enemies of insect pests in crop habitats, typically by intentional provision of flowering plants as food resources. Ideally, these flowering plants should be inherently attractive to natural enemies to ensure that they are frequently visited. We review the chemical ecology of floral resources in a conservation biological control context, with a focus on insect parasitoids. We highlight the role of floral volatiles as semiochemicals that attract parasitoids to the food resources. The discovery that nectar-inhabiting microbes can be hidden players in mediating parasitoid responses to flowering plants has highlighted the complexity of the interactions between plants and parasitoids. Furthermore, because food webs in agroecosystems do not generally stop at the third trophic level, we also consider responses of hyperparasitoids to floral resources. We thus provide an overview of floral compounds as semiochemicals from a multitrophic perspective, and we focus on the remaining questions that need to be addressed to move the field forward. Expected final online publication date for the

[EN] BACKGROUNDThe optimisation of the lure is essential for the implementation of trapping systems to control insect pests. In this work, the response of the red palm weevil (RPW), Rhynchophorus ferrugineus Olivier, to increasing emission rates of its aggregation pheromone (ferrugineol) and the efficacy of a convenient synthetic kairomone based on fermentation odours (ethyl acetate and ethanol) have been evaluated in different years and locations along the Mediterranean basin. RESULTSIn general, although capture data and emission had noticeable variability among locations, significantly fewer RPW were captured in pyramidal Picusan (R) traps with the lowest ferrugineol emission rates tested (0.6-3.8 mg day(-1)). Captures increased rapidly with ferrugineol emission up to 4-5 mg day(-1); then, higher emission rates did not improve or reduce captures, up to the highest emission rate tested of 50.9 mg day(-1). Thus, there is no evidence of an optimum release rate corresponding to a maximum of RPW catches. Traps baited with the synthetic kairomone (1:3 ethyl acetate/ethanol) captured 1.4-2.2 times more total weevils than traps baited only with ferrugineol. Moreover, in most of the locations, the synthetic blend was at least as effective as the local coattractants used (plant material + molasses). CONCLUSIONSFerrugineol emission rate can vary in a wide range without significantly affecting RPW response. Coattractants based on fermenting compounds, ethyl acetate and ethanol, are able to improve the attractant level of ferrugineol and could be employed to replace non-standardised natural kairomones in RPW trapping systems after further optimisation of their proportions and doses. (c) 2016 Society of Chemical Industry, The research leading to these results has received funding from the 7th European Union Framework Programme under Grant Agreement FP7 KBBE 2011-5-289566 (PALM PROTECT). The authors would like to thank Yaakov Nakashe and Ami Landau for field assistance in the trials conducted in Israel, and Gikarakis Dimitrios and Fokas Vlasis for field assistance in the trials conducted in Greece.

The Painted bug, Bagrada hilaris Burmeister is an herbivorous insect native of Asia and Africa, invasive in Southern Europe and North America where it causes major damage on various vegetable crops mainly belonging to Brassicaceae family. Young plants at cotyledon stage of B. oleracea are particularly attractant and susceptible to B. hilaris feeding activity. To elucidate the main volatile organic compounds (VOCs) involved in the attraction of B. hilaris individuals toward the host plant B. oleracea, laboratory experiments were carried out using vertical Y-shaped olfactometer and electroantennographic techniques (EAG). Both adults and late nymphal instars were used in these experiments. Olfactometer experiments were done with young seedlings (one week old) and their VOCs headspace extract collected by porapak Q and eluted in hexane. The VOCs elution was tested and afterward fractionated by silica gel column in order to assess the active fraction. Result indicated attraction of adults and nymphs toward volatiles of living seedlings and their VOCs extract. Furthermore, the non-polar fraction elicited attraction while no response was determined by polar fractions. These results were confirmed by the EAG experiment: only the whole extract and non-polar fraction elicited significant response. These data suggest that the non-polar compounds emitted from young seedlings of B. oleracea can play an important role in B. hilaris host location processes.

Chemical footprints deposited by herbivorous pentatomid host bugs hosts when walking on the plant are adsorbed by leaf surfaces and perceived as substrate borne semiochemicals by scelionid egg parasitoids during host selection process. They act as indirect host-related cues, as they are not able to “promise” to parasitoid females the presence of the suitable host stage, but they drive them in the areas where their hosts are potentially present. Once in contact with host chemical footprints, scelionid wasps evidence an innate arrestment response characterized by an intense searching behaviour on host-contaminated areas. Exploiting of these cues allows the parasitoids to optimize their searching behaviour, since wasp females are able to discriminate the host gender and to distinguish associated from non-associated hosts. Here we investigated the response of Trissolcus basalis females, a natural enemy of several pentatomid species to chemical footprints left by Halyomorpha halys (Heteroptera: Pentatomidae) an herbivorous alien bug that shares the same environments as native pentatomid pests. In laboratory conditions we tested T. basalis ability to discriminate between female and male H. halys footprints. We also quantified the walking behaviour of T. basalis when they are rewarded by an oviposition experience on H. halys eggs. The outcomes are discussed by evaluating the possible consequences of alien insect spread on local parasitoid foraging behaviour.

The Brown Marmorated Stink Bug Halyomorpha halys (Heteroptera: Pentatomidae), is a very polyphagous pest of fruit crops, horticultural crops and ornamentals. Native from eastern Asia, this invasive species was recorded for the first time in Modena in 2012 and is now spreading in Northern and Central Italy. With its establishment in the invaded areas, new interactions with native tri-trophic systems (plants - stink bugs - parasitoids) are expected. A plant attacked by an ovipositing stink bug may respond by the emission of induced plant synomones, which are exploited by egg parasitoids for host location (indirect defences). This mechanism had been studied for coevolved tritrophic systems at a behavioural, chemical and molecular level, and is now under investigation for novel interactions between H. halys and the native egg parasitoids Trissolcus basalis, T. cultratus (Hymenoptera: Platygastridae) and Anastatus bifasciatus (Hymenoptera: Eupelmidae). Additionally, plants may react directly to oviposition by reducing the development and fitness of new brood (priming of direct defences). This aspect is also under investigation in plants attacked by ovipositing H. halys females. Molecular mechanisms of plant defence responses are evaluated through expression analyses (RTqPCR) of marker genes for the salicylic and the octadecanoid pathways, comparing novel versus native systems to assess similarities and differences. Our research would be useful for evaluation of the effects of H. halys on native tritrophic systems and, on the other hand, biological control perspectives against this invasive species.

Populations of herbivorous insects are naturally consumed by other predacious or predatory insect species. These entomophagous insects are thus plant-dwelling organisms that use the plant for several vital functions and are affected by plant traits at the evolutionary, organism and population levels. Many entomophagous species are used for the biological control of insect pests worldwide. The aim of this chapter is to provide an exhaustive review of mechanisms underlying the interactions between plants and entomophagous insects, including those governing life history traits at the individual level, as well as those acting on population and community structure and dynamics. We detail how properties of host-infested plants determine parasitism behaviour, development (in the case of parasitoids) and nectar consumption by adult entomophagous insects. We detail how plants respond to and benefit from natural enemies attacking insect herbivores. We also illustrate how plant architecture, the vegetation communities and their climatic correlates can influence predator and parasitoid behaviour and populations. This chapter considers the biology and ecology of the interactions and mentions some implications for the biological control of plant pests.

Ongoing studies by our group showed that the outcome of the intrinsic competition between two solitary egg parasitoids, Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) and Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae), is dominated by O. telenomicida. In this article we investigated the role played by the ovipositing O. telenomicida female in the suppression of a T. basalis competitor. Laboratory experiments were conducted by allowing an O. telenomicida female to puncture the eggs of Nezara viridula (L.) (Heteroptera: Pentatomidae) with her ovipositor (= no oviposition) or to parasitize them. The results show that O. telenomicida relies on some physiological mechanisms to mediate its interspecific intrinsic competition with T. basalis. In fact, the emergence of T. basalis was strongly reduced in host eggs that were parasitized either before or after being punctured by O. telenomicida at fixed time intervals (5, 15, 30, or 45 h). The low percentage of emergence of T. basalis (ranging from approximately 420%) was a consequence of the delay and growth rate reduction of larval development. Furthermore, the percentage of eclosion of N. viridula nymphs was negatively affected by the O. telenomicida females punctures (96% from healthy host eggs, 4% from punctured host eggs). Host eggs punctured or oviposited in by O. telenomicida showed alterations in the ooplasm including some melanized-like areas near the hole made with the ovipositor; such alterations indicate that the adult parasitoid releases substances that affect the host eggs survival. These results suggest that the O. telenomicida female influences both the physiological interspecific parasitoid-parasitoid interaction, as well as the host-parasitoid interaction, providing, for the first time in egg parasitoids, evidence that physiological suppression of some competitive egg parasitoids is mediated by the ovipositing female.

Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), the tomato leaf miner, is one of the most devastating pests affecting tomato crops in Italy. Management of T. absoluta was assessed in open-field tests using three biorational insecticides, Azadirachtin, Bacillus thuringiensis var. kurstaki, and Beauveria bassiana, and a combination of three synthetic insecticides, Emamectin, Indoxacarb and Metaflumizone, as a control treatment. Our results showed that only the combination of Azadirachtin – B. thuringiensis was able to reduce the impact of tomato leaf miner on the fruit’s marketable production similarly to the control treatment. This finding suggests that biorational insecticides are a good alternative to synthetic ones. Possible use of biorational insecticides in the management of tomato leaf miner in organic farming system is discussed.

We analyse the effects of environmental noise in three different biological systems: (i) mating behaviour of individuals of 'Nezara viridula' (L.) (Heteroptera Pentatomidae); (ii) polymer translocation in crowded solution; (iii) an ecosystem described by a Verhulst model with a multiplicative Lèvy noise. Specifically, we report on experiments on the behavioural response of 'N. viridula' individuals to sub-threshold deterministic signals in the presence of noise. We analyse the insect response by directionality tests performed on a group of male individuals at different noise intensities. The percentage of insects which react to the sub-threshold signal shows a non-monotonic behavior, characterized by the presence of a maximum, for increasing values of the noise intensity. This is the signature of the non-dynamical stochastic resonance phenomenon. By using a "hard" threshold model we find that the maximum of the signal-to-noise ratio occurs in the same range of noise intensity values for which the behavioral activation shows a maximum. In the second system, the noise driven translocation of short polymers in crowded solutions is analyzed. An improved version of the Rouse model for a flexible polymer has been adopted to mimic the molecular dynamics, by taking into account both the interactions between adjacent monomers and introducing a Lennard-Jones potential between non-adjacent beads. A bending recoil torque has also been included in our model. The polymer dynamics is simulated in a two-dimensional domain by numerically solving the Langevin equations of motion. Thermal fluctuations are taken into account by introducing a Gaussian uncorrelated noise. The mean first translocation time of the polymer center of inertia shows a minimum as a function of the frequency of the oscillating forcing field. In the third ecosystem, the transient dynamics of the Verhulst model perturbed by arbitrary non-Gaussian white noise is investigated. Based on the infinitely divisible distribution of the Lèvy process we study the nonlinear relaxation of the population density for three cases of white non-Gaussian noise: (i) shot noise, (ii) noise with a probability density of increments expressed in terms of Gamma function, and (iii) Cauchy stable noise. We obtain exact results for the probability distribution of the population density in all cases, and for Cauchy stable noise the exact expression of the nonlinear relaxation time is derived. Moreover starting from an initial delta function distribution, we find a transition induced by the multiplicative Lèvy noise, from a trimodal probability distribution to a bimodal probability distribution in asymptotics. Finally we find a nonmonotonic behavior of the nonlinear relaxation time as a function of the Cauchy stable noise intensity.

Palm Protect is an EU-funded program (2012-14) entitled: “Strategies for eradication and containment of invasive palm borers, Rhynchophorus ferrugineus and Paysandisia archon. The project aims at throwing light on aspects of the pest biology in Europe, which are unknown and preclude efficient control, validating new and reliable methods for detection and control, and implementing them into strategies for eradication of the palm borers both at the points of entry in the EU and in the infested areas. The project also aims at providing with an economic analysis to value palm services and management options and to disseminate the findings to the stakeholders. Palm Protect associates 12 research organisations, 1 SME, UK, France, Greece, Italy, Slovenia, Spain, Israel and Egypt. It is based on 6 actions: Management, Biology, Detection, Control, Economics and Dissemination. France contributes by INRA (Versailles et Sophia Antipolis) and CIRAD, which are particularly involved to provide new fundamentals about adult mobility, semiochemicals and parasitoids. The results will make it possible to improve European regulation and its efficacy from a consolidated scientific background in compliance with the standards in force for pest control; Palm Protect est un programme financé par l’UE (2012-14) intitulé ‘Stratégies pour l'éradication et le confinement des ravageurs invasifs des palmiers P. archon et R. ferrugineus’. Il a pour objectifs d’éclairer les éléments inconnus de la biologie en Europe de ces espèces qui limitent l’efficacité de la lutte, de valider des méthodes et des stratégies fiables et nouvelles pour leur détection, leur gestion et leur éradication tant aux points d’entrée que dans les zones contaminées. Palm Protect diffusera le fruit de ces travaux à tous les acteurs de la filière ‘palmiers’. Le programme associe 12 organismes de recherche, une PME, le Royaume-Uni, l’Espagne, la France, la Grèce, l’Italie, la Slovénie, Israël et L’Egypte. Il comprend 6 actions : Coordination, Biologie, Détection et surveillance, Lutte, Economie et Diffusion des acquis. La France contribue par l'INRA (Versailles et Sophia Antipolis) et le CIRAD, et s’implique fortement dans l’acquisition de connaissances nouvelles sur le déplacement des adultes, les médiateurs chimiques et les parasitoïdes. Les résultats serviront de base pour améliorer la réglementation européenne et son efficacité à partir de données scientifiques en application des règles générales en vigueur pour le contrôle des bio-agresseurs

Palm Protect est un programme financé par l’UE (2012-14) intitulé ‘Stratégies pour l'éradication et le confinement des ravageurs invasifs des palmiers P. archon et R. ferrugineus’. Il a pour objectifs d’éclairer les éléments inconnus de la biologie en Europe de ces espèces qui limitent l’efficacité de la lutte, de valider des méthodes et des stratégies fiables et nouvelles pour leur détection, leur gestion et leur éradication tant aux points d’entrée que dans les zones contaminées. Palm Protect diffusera le fruit de ces travaux à tous les acteurs de la filière ‘palmiers’. Le programme associe 12 organismes de recherche, une PME, le Royaume-Uni, l’Espagne, la France, la Grèce, l’Italie, la Slovénie, Israël et L’Egypte. Il comprend 6 actions : Coordination, Biologie, Détection et surveillance, Lutte, Economie et Diffusion des acquis. La France contribue par l'INRA (Versailles et Sophia Antipolis) et le CIRAD, et s’implique fortement dans l’acquisition de connaissances nouvelles sur le déplacement des adultes, les médiateurs chimiques et les parasitoïdes. Les résultats serviront de base pour améliorer la réglementation européenne et son efficacité à partir de données scientifiques en application des règles générales en vigueur pour le contrôle des bio-agresseurs, Palm Protect is an EU-funded program (2012-14) entitled: “Strategies for eradication and containment of invasive palm borers, Rhynchophorus ferrugineus and Paysandisia archon. The project aims at throwing light on aspects of the pest biology in Europe, which are unknown and preclude efficient control, validating new and reliable methods for detection and control, and implementing them into strategies for eradication of the palm borers both at the points of entry in the EU and in the infested areas. The project also aims at providing with an economic analysis to value palm services and management options and to disseminate the findings to the stakeholders. Palm Protect associates 12 research organisations, 1 SME, UK, France, Greece, Italy, Slovenia, Spain, Israel and Egypt. It is based on 6 actions: Management, Biology, Detection, Control, Economics and Dissemination. France contributes by INRA (Versailles et Sophia Antipolis) and CIRAD, which are particularly involved to provide new fundamentals about adult mobility, semiochemicals and parasitoids. The results will make it possible to improve European regulation and its efficacy from a consolidated scientific background in compliance with the standards in force for pest control

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BACKGROUND: Interspecific competition in insect parasitoids is an important ecological phenomenon that has relevant implications for biological pest control. To date, interspecific intrinsic (=larval) competition has been intensively studied, while investigations on extrinsic (=adult) competition have often lagged behind. In this study we examined the role played by parasitoid reproductive traits and host clutch size on the outcome of extrinsic competition between Trissolcus basalis (Wollaston) and Ooencyrtus telenomicida (Vassiliev), two egg parasitoids of the pest Nezara viridula (L). Laboratory experiments were conducted by allowing both parasitoid species to exploit an egg mass made of 10, 20, 30, or 40 hosts through single or simultaneous releases. Furthermore, under field conditions, egg masses consisting of 10 or 40 hosts were exposed in a tomato crop in order to validate laboratory investigation. RESULTS: The results show that the egg mass size is an important predictor of extrinsic competition in our study system as a higher proportion of T. basalis emerged from large egg masses, while O. telenomicida dominated in small egg masses. Analysis of reproductive traits of parasitoid species indicates that T. basalis has superior abilities in host exploitation compared with O. telenomicida. CONCLUSIONS: We found that contrasting reproductive traits of two competing egg parasitoid species facilitate coexistence on a shared stink bug host. This work also highlights the importance to consider extrinsic competitive interactions between parasitoid species in a biological control perspective. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Competition for hosts is a common ecological interaction in insect parasitoids. In the recent years, it has become increasingly evident that microorganisms can act as ‘hidden players’ in parasitoid ecology. In this review, we propose that parasitoid competition should take into consideration the microbial influence. In particular, we take a tritrophic perspective and discuss how parasitoid competition can be modulated by microorganisms associated with the parasitoids, their herbivore hosts, or the plants attacked by the herbivores. Although research is still in its infancy, recent studies have shown that microbial symbionts can modulate the contest outcome. The emerging pattern is that microorganisms not only affect the competitive traits of parasitoids but also the fighting arena (i.e. the herbivore host and its food plant), in which competition takes place. We have also identified important gaps in the literature that should be addressed in future studies to advance our understanding about parasitoid competition.

This chapter reviews the literature on semiochemical-parasitoid systems in perennial crops. The first part of the chapter analyses the possible effects of pheromone-based tactics on parasitoid efficacy. In both orchards and vineyards, the most successful application of synthetic sex pheromones has been their use as mating disruptants. It also discusses the possibility of using parasitoid pheromones to directly affect parasitoid behaviour. The second part of the chapter summarizes research in orchards and vineyards that has tested whether synthetic chemical cues such as herbivore-induced plant volatiles (HIPVs) and host-associated volatiles (HAVs) can be used to manipulate parasitoid behaviour, and specifically to enhance their searching efficacy. Finally, the chapter considers the interaction of semiochemical–parasitoid systems with habitat management as novel combined strategies that have recently been developed to improve the success of semiochemical-based integrated arthropod pest management.

Floral nectar is ubiquitously colonized by a variety of microorganisms among which yeasts and bacteria are the most common. Microorganisms inhabiting floral nectar can alter several nectar traits, including nectar odor by producing microbial volatile organic compounds (mVOCs). Evidence showing that mVOCs can affect the foraging behavior of insect pollinators is increasing in the literature, whereas the role of mVOCs in altering the foraging behavior of third-trophic level organisms such as insect parasitoids is largely overlooked. Parasitoids are frequent visitors of flowers and are well known to feed on nectar. In this study, we isolated bacteria inhabiting floral nectar of buckwheat, Fagopyrum esculentum (Polygonales: Polygonaceae), to test the hypothesis that nectar bacteria affect the foraging behavior of the egg parasitoid Trissolcus basalis (Hymenoptera: Scelionidae) via changes in odors of nectar. In behavioral assays, we found that T. basalis wasps are attracted toward nectar fermented by 4 out of the 14 bacterial strains isolated, which belong to Staphylococcus epidermidis, Terrabacillus saccharophilus (both Firmicutes), Pantoea sp. (Proteobacteria), and Curtobacterium sp. (Actinobacteria). Results of chemical investigations revealed significant differences in the volatile blend composition of nectars fermented by the bacterial isolates. Our results indicate that nectar-inhabiting bacteria play an important role in the interactions between flowering plants and foraging parasitoids. These results are also relevant from an applied perspective as flowering resources, such as buckwheat, are largely used in agriculture to promote conservation biological control of insect pests.