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Background and Aims Intercropping of truffle-producing trees with aromatic plants is used to improve profitability of truffle orchards during the initial 4–7 years. However, after that period the viability of this system is challenged by the appearance of brûlés, an area around host tree characterised by scarce plant cover where the fungus exhibits allelopathic activity. We aimed to investigate the ecological interactions between these crops and between their associated mycorrhizal fungi in adult truffle plantations. Methods We simulated two intercropping systems, truffle oak – lavender and truffle oak – rosemary in their adult stage. We analysed and compared aromatic plants and soil samples inside and outside the brûlés during the first year of the aromatic plants in the field. Results We found a strong negative relation of brûlés with the growth of the aromatic plants, although not a decrease in the arbuscular mycorrhizal colonization of their roots. The essential oil yield and composition of aromatic plants was affected by brûlés. The extraradical truffle mycelium was not significantly affected by the presence of aromatic plants. Conclusions The growth and yield of aromatic plants was impaired during their first year growing in brûlés, whereas no negative effect of aromatic plants on truffle fruiting potential was found. The study improves our understanding of the mechanisms influencing the viability of the truffle tree – aromatic plant intercropping and the possible technical challenges. info:eu-repo/semantics/acceptedVersion

Aphis frangulae (Hemiptera: Aphididae) is a major pest of the laurel forest endemic Frangula azorica (Rosales: Rhamnaceae) produced in nursery conditions by the Forestry Services of the Azores (Portugal). The suitability of A. frangulae for the development and reproduction of a potential biological control agent, Scymnus nubilus (Coleoptera: Coccinellidae), was assessed under laboratory conditions (25 ± 1 °C, 75 ± 5% RH, 16:8 L:D photoperiod). The predation potential of S. nubilus was also assessed. Scymnus nubilus 4th instar larvae and pupae successfully completed development in 9.0 ± 0.2 days. The 4th instar larvae ate 15.1 aphids per day, corresponding to 1.52 mg of biomass ingested. On A. frangulae, S. nubilus females took 5.5 ± 0.3 days to start oviposition and an average of 135 ± 12 eggs were laid per female over the first 15 days of oviposition. Field tests showed that S. nubilus 4th instar larvae were more efficient in controlling the pest in closed systems (isolated aphid colonies) and the effect was more pronounced at high predator densities within three days. In open systems, the aphid natural control was higher than initially expected. This work highlights the role of the large aphidophagous guild present in forestry nurseries. The results of this study show that A. frangulae is an essential prey species for S. nubilus and therefore the predator can be used in pest management programs against this pest. However, further studies focusing on different biological control tactics (inundative or inoculative) are required to assess more accurately the effectiveness of S. nubilus as a biological control agent against A. frangulae. This research was supported by the Official Forestry Services from the Regional Government of the Azores, through the research project PICA 'Utilização de agentes de controlo biológico para o combate a populações de afídeos em plantas endémicas produzidas em viveiro', and PICONNIA "Controlo biológico de populações de pragas de plantas endémicas produzidas em viveiro", in direct collaboration with the Forestry Engineers Carina Nóbrega and Catarina Quintela. info:eu-repo/semantics/publishedVersion

Agricultural intensification is affecting the biological control of insect pests, an important component for sustainable crop production. To understand the changing patterns of insect abundance within an agroecosystem, it is necessary to disentangle the trophic interactions between species, and metabarcoding is an excellent alternative to show them. In the Ebro Basin (NE Iberian Peninsula), agricultural landscapes are composed of a mosaic of crops scattered with natural and semi-natural habitats, where the presence of Orius spp., used as biocontrol agents, is well known. To shed light on their predatory role in this area, a previously developed metabarcoding multi-primer method has been used to study the arthropod and plant most frequently resources consumed by some field-collected Orius, sampled at different dates in a peach and an alfalfa adjacent crop. Their high-throughput sequencing (HTS) analysis showed the consumption of 15 arthropod and 12 plant taxa. Eight of them were consumed by O. laevigatus, six by O. majusculus and 23 by O. niger. The obtained results showed that HTS is a powerful tool in studies of trophic interactions in agroecosystems. Among the detected arthropods, other natural enemies were present, showing a certain degree of intraguild predation, which has been demonstrated by developing a new added strategy in the bioinformatic analysis. Detected plant consumption indicates that Orius forages on several plant species, showing their movement from them to the sampled crops. These plants could have a potential role in attracting or maintaining these predators in both crops in biological control strategies.

Conservation biological control involves manipulation of the environment to enhance the efectiveness of natural enemies in controlling crop pests. In this study, we combined historical data, sticky trap sampling of tomato greenhouses and beat sampling of adjacent vegetation to identify which greenhouse characteristics, habitat management practices and landscape features favour an early colonisation of tomato greenhouses by the key mirid predator Macrolophus pygmaeus and its establishment in NE Spain. Results show that landscape composition and the use of Calendula ofcinalis banker plants inside the greenhouse are key factors. In general, greater amounts of herbaceous semi-natural cover at the landscape scale promoted M. pygmaeus colonisation, while the use of C. ofcinalis banker plants encouraged M. pygmaeus colonisation independently of the landscape context. We identifed host plants adjacent to tomato greenhouses that sustain M. pygmaeus populations; however, they did not have a major efect on M. pygmaeus colonisation compared to larger landscape and banker plant efects. Early colonisation of greenhouses by this predator species also translated into lower accumulated incidence of pests at the end of the sampling period. This study demonstrates the importance of active habitat management practices in promoting the early arrival of M. pygmaeus in greenhouses with delayed spontaneous colonisation. This study was funded by EU-funded projects, EUCLID (Project Number: 633999-2) and EMPHASIS (Project Number: 634179-2), the project AGL2016-77373-C2-1-R (Spanish Ministry of Economy and Competitiveness) and the CERCA Programme of the Generalitat de Catalunya. AA was partly supported by a Ramón Areces fellowship while writing this manuscript.

There is increasing evidence that microorganisms, particularly fungi and bacteria, emit volatile compounds that mediate the foraging behaviour of insects and therefore have the potential to affect key ecological relationships. However, to what extent microbial volatiles affect the olfactory response of insects across different trophic levels remains unclear. Adult parasitoids use a variety of chemical stimuli to locate potential hosts, including those emitted by the host’s habitat, the host itself, and microorganisms associated with the host. Given the great capacity of parasitoids to utilize and learn odours to increase foraging success, parasitoids of eggs, larvae, or pupae may respond to the same volatiles the adult stage of their hosts use when locating their resources, but compelling evidence is still scarce. In this study, using Saccharomyces cerevisiae we show that Trichopria drosophilae, a pupal parasitoid of Drosophila species, is attracted to the same yeast volatiles as their hosts in the adult stage, i.e. acetate esters. Parasitoids significantly preferred the odour of S. cerevisiae over the blank medium in a Y-tube olfactometer. Deletion of the yeast ATF1 gene, encoding a key acetate ester synthase, decreased attraction of T. drosophilae, while the addition of synthetic acetate esters to the fermentation medium restored parasitoid attraction. Bioassays with individual compounds revealed that the esters alone were not as attractive as the volatile blend of S. cerevisiae, suggesting that other volatile compounds also contribute to the attraction of T. drosophilae. Altogether, our results indicate that pupal parasitoids respond to the same volatiles as the adult stage of their hosts, which may aid them in locating oviposition sites. info:eu-repo/semantics/acceptedVersion

Tuta absoluta Meyrick (Lepidoptera: Gelechiidae) is considered one of the main pests threatening tomato production worldwide. In the Mediterranean, the use of predatory mirids is widespread, and although several larval parasitoid species have been recorded in the area, their contribution to the biological control of the pest is often neglected. With the general objective of improving the biological control of T. absoluta, our field study aimed to determine the relative abundance of natural enemies associated with T. absoluta in tomato fields and to assess whether insectary plants placed in the vicinity of vegetable crops would help to improve functional biodiversity in the farms. The study was conducted during two years in six commercial tomato fields in Northeast Spain that were managed using an integrated pest management program based on predatory mirid conservation. Our results indicated that Necremnus tutae Ribes & Bernardo (Hymenoptera: Eulophidae) was by far the main natural enemy responsible for larval parasitism of T. absoluta. The flowering plants used in the present study were attractive to several natural enemies that are of interest not only for tomato but also for other vegetable crops coexisting at the farm level, including parasitoid wasps, hoverflies, and other important beneficials, such as Orius spp., ladybeetles and predatory thrips. info:eu-repo/semantics/acceptedVersion

This study assesses the feasibility of using natural enemies for the control of Acanthoscelides obtectus Say and Zabrotes subfasciatus Boheman (Coleoptera: Chrysomelidae), key pests of stored dried beans, Phaseolus vulgaris L. (Fabales: Fabaceae). The predatory mites Blattisocius tarsalis Berlese (Acari: Ascidae) and Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) were able to prey on A. obtectus eggs, reducing the bruchid population by more than 60% under both controlled and warehouse conditions. Therefore, they show good potential as biological agents for controlling this pest. The larval parasitoids Anisopteromalus calandrae Howard and Lariophagus distinguendus Förster (Hymenoptera: Pteromalidae) were both moderately effective (34–38% reduction) at suppressing A. obtectus populations, but when A. calandrae was combined with B. tarsalis, a significant improvement in control efficacy (81% reduction in emergence) was observed. Therefore, the release of A. calandrae combined with B. tarsalis seems to be a promising strategy for controlling A. obtectus. Neither B. tarsalis nor A. swirskii were able to prey on Z. subfasciatus eggs. Only the parasitoid A. calandrae was moderately effective (39% reduction) at supressing Z. subfasciatus populations. Further testing is needed to identify other natural enemies that can complement the action of A. calandrae in reducing Z. subfasciatus populations. info:eu-repo/semantics/acceptedVersion

The β-aminobutyric acid (BABA) is a plant defense priming compound highly effective in controlling important tomato diseases and plant-parasitic nematodes. It has also been shown to induce resistance against phytophagous insects such as aphids. This study examines the effect of BABA on the performance of the tomato pest Bemisia tabaci (MEAM 1, previously known as Biotype B) and its zoophytophagous predator Macrolophus pygmaeus under laboratory and greenhouse conditions. Tomato plants were treated with BABA 25 mM applied by soil drenching. The effect of BABA on the fertility and juvenile development of two generations of B. tabaci and M. pygmaeus was evaluated. Our results showed no effect of BABA on the juvenile development or adult fecundity/fertility of both the whitefly and its predator. The non-interference of BABA with M. pygmaeus and B. tabaci assures that the control of the whitefly with this mirid bug will not be affected when this elicitor is applied to the crop. Further studies are needed to clarify the mechanisms underlying BABA-plant-whitefly-predatory myrids interactions. info:eu-repo/semantics/acceptedVersion

A qPCR-based method was developed to detect and quantify Podosphaera pannosa, the main causal agent of peach powdery mildew. A primer pair was designed to target part of the ITS region of the fungal ribosomal DNA, which proved to be highly specific and sensitive. A minimum of 2.81 pg µL− 1 of P. pannosa DNA and 6 conidia mL− 1 in artificially-prepared conidia suspensions were found to be the limit of detection. Moreover, a quantification of conidia placed on plastic tapes commonly used in volumetric air samplers was performed. Regression equations on conidia quantification obtained either from aqueous conidia suspensions or conidia placed on plastic tapes were similar. The protocol was further validated in field conditions by estimating the number of P. pannosa conidia obtained with an air sampler, by both microscopic and molecular quantification. Both techniques detected the peaks of conidia production during a 4-month sampling period, and a significant correlation (r = 0.772) was observed between both quantification methods. Additionally, the molecular method was applied to detect latent fungal inoculum in different plant parts of peach trees. The pathogen was detected mainly on the bark of affected twigs, and to a lesser extent, in foliar buds. The method developed here can be applied in the study of P. pannosa epidemiology and can help in improving the management of this pathogen through its early detection and quantification., This research was funded by Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria (INIA), Spain, project RTA2013-00004-C03-01, and with matching funds from the European Regional Development Fund (ERDF). Jordi Luque was supported by the CERCA Programme, Generalitat de Catalunya. Neus Marimon was supported by INIA with a predoctoral grant (CPD-2015-0142).

Venturia canescens and Habrobracon hebetor are cosmopolitan parasitoids found in large numbers in food processing facilities in northeastern Spain and in many other countries. These parasitoids attack larvae of pyralid moths, which are important pests of stored products and food industries worldwide. In this study, we evaluated the performance of these two parasitoids when offered single or combined populations of Plodia interpunctella and Ephestia kuehniella, since these can occur together in storehouses. We tested the parasitoid’s performance in small cages under laboratory conditions and small experimental storerooms (≈ 30 m3). In the laboratory, the two parasitoids were able to reduce pyralid populations by more than 37% over a 48-h period (40–44% for E. kuehniella, 37–41% of P. interpunctella and 53–55% of both hosts when offered together). Similar results were obtained in small storerooms after 10 days: a > 35% reduction in pyralid populations also was obtained when host species were offered either singly (E. kuehniella or P. interpunctella) or in combination (E. kuehniella + P. interpunctella) (35–57% for E. kuehniella, 40–54% of P. interpunctella and 41–46% of both hosts when offered together). Parasitism was consistently good from June through November (mean temperatures from 18 to 28 °C and 9.5 to 15 h of daylight). Therefore, both parasitoids, single or in combination, can be efficient biological control agents of these two pyralid moths when infesting stored food facilities. info:eu-repo/semantics/acceptedVersion