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Le diverse fasi che caratterizzano l’attacco della pianta da parte del fitofago (contatto, alimentazione ed ovideposizione) inducono l’attivazione di meccanismi di difesa nell’ospite. E’ noto che le piante emettono composti volatili indotti in seguito all’attacco del fitofago e che questi volatili sono in grado di richiamare i parassitoidi. Nel caso specifico degli ooparassitoidi, tali difese indirette si esplicitano mediante rilascio di HIPV (herbivore-induced plant volatiles) ed in particolare di OIPV (oviposition-induced plant volatiles). Ad oggi non ci sono studi inerenti il ruolo giocato dalle tracce rilasciate dal fitofago sulla superficie vegetale nell’induzione di volatili utilizzati dagli ooparassitoidi. In questo lavoro è stata valutata la risposta dell’ooparassitoide Trissolcus basalis ai volatili indotti in Vicia faba dalle tracce lasciate sulla superficie fogliare dall’ospite Nezara viridula. Sono stati condotti biosaggi in olfattometro chiuso ad Y per valutare la risposta di T. basalis a piante contaminate con le tracce lasciate da N. viridula sulla pagina inferiore o superiore della foglia di fava. I risultati hanno evidenziato che le tracce lasciate dalla cimice verde sulla pagina inferiore delle foglie determinano l’induzione di FIPV (footprint-induced plant volatiles) che alterano il comportamento di foraggiamento del parassitoide. L’emissione di FIPV è stata evidenziata anche nel caso di foglie rovesciate indicando un marcato ruolo della localizzazione dello stress. Tale ruolo è stato ulteriormente confermato da altri biosaggi in cui l’ovideposizione, combinata con l’alimentazione e le tracce delle femmine della cimice verde, induce l’emissione di volatili attivi sul parassitoide solo quando è localizzata a livello della superficie inferiore delle foglie. I risultati ottenuti in questo lavoro hanno contribuito a chiarire il ruolo delle tracce nell’emissione volatile da parte della pianta ed hanno evidenziato il ruolo della pagina inferiore delle foglie nel mediare la comunicazione chimica tra T. basalis ed il suo ospite.

Studies on semiochemical communication have demonstrated that broad bean plant, Vicia faba, emits volatile synomones induced by feeding and oviposition activities of the southern green stink bug, Nezara viridula, which recruit the egg parasitoid Trissolcus basalis. However plants growing in agro-ecosystems can be attacked by several herbivore species that could affect both above and belowground plant tissues with possible consequences for parasitoid recruitment. For example, broad bean plants can also be attacked by the leaf weevil, Sitona lineatus, and simultaneous attacks by the southern green stink bug and the leaf weevil can occur in agro- ecosystems. The purpose of this work was to investigate the effects of dual biotic stresses, the host N. viridula and the non-host S. lineatus, on V. faba volatile synomones that recruit T. basalis. The response of wasp females to V. faba volatiles was investigated in a Y-tube olfactometer testing the following treatments: (1) plant damaged by N. viridula feeding and oviposition; (2) plant damaged by S. lineatus feeding; (3) plant mechanically damaged to resemble S. lineatus feeding; (4) plants damaged by N. viridula feeding and oviposition and by mechanical damages; (5) plants damaged by N. viridula feeding and oviposition and by S. lineatus feeding; (6); healthy plants. Volatile organic compounds emitted from tested plants were also chemically analyzed by Gas Chromatography – Mass Spectrometry (GC-MS). The results showed that dual biotic stresses affect V. faba volatile synomones decreasing their attractiveness towards T. basalis. Chemical analysis indicated qualitative differences between volatiles emitted by V. faba plants in response to N. viridula feeding and oviposition and volatile emitted as consequence of dual insect infestation. The ecological consequences of these results in terms of multi-trophic interactions are discussed.

Interspecific competitions among parasitoids can affect community structures, and, as a consequence at applicative level, biological control programs. For example, competitions can cause local displacement of inferior species or niche separation. However, the coexistence of species attacking the same host is possible when they adopt different strategies to exploit the resource. In this work we evaluated in field and semi-field conditions intraguild interactions between two egg parasitoids, Trissolcus basalis and Ooencyrtus telenomicida exploring egg masses of Nezara viridula. In semi-field trials, pepper plants were covered with mesh net creating small cages with five plants inside. In each cage, egg masses were placed on plants and then T. basalis and O. telenomicida were released individually or simultaneously. After one week egg masses were recollected. The results showed that T. basalis achieves a high parasitism level when released alone but suffers competition by O. telenomicida in case of simultaneous releasing. Field trials were conducted in tomato fields from May to October in two consecutive years, by monitoring 8 sentinel egg masses placed weekly on plants and recollected one week later, and by collecting naturally laid egg masses that were parasitized only by T. basalis, only by O. telenomicida or by both species. The outcomes showed that T. basalis occurs from June to October, whereas O. telenomicida mainly in July and August, and the former achieves a higher impact on the natural host population than the latter, even when multiparasitism occurs. The ecological role of these results is discussed.

In Sicily, field collections of egg masses of the southern green stink bug, Nezara viridula (L.) (Heteroptera:Pentatomidae), revealed that two solitary parasitoids, Trissolcus basalis (Wollaston) (Hymenoptera: Platygastridae) and Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae), can exploit the same egg mass. Previous finding showed that parasitoid species differ in host location and larval competitive abilities and a host finding-larval competition trade-off may be important for coexistence. The aim of this work was to evaluate the role played by the host egg mass size and the importance of species reproductive capacities in the outcome of interspecific competition. Under laboratory conditions, parasitoids were introduced in an arena and allowed to exploit an egg mass made of 10, 20, 30 or 40 unparasitized hosts. Under field conditions, unparasitized egg masses consisting of 10 or 40 hosts were exposed in a tomato crop and recollected after one week. To assess the reproductive capacity of T. basalis and O. telenomicida, investigations were conducted by: 1) counting the number of ovarian eggs of female parasitoids; 2) measuring the size of the fresh laid egg; 3) recording the host handling time. Results indicated that a higher proportion of T. basalis emerged from large egg masses (N=40) while O. telenomicida dominated in small egg mass (N=10); intermediate results were obtained from egg masses of medium size. Analysis of reproductive capacities of parasitoid species indicated that T. basalis has superior abilities in exploiting unparasitized egg masses compared with O. telenomicida. The ecological role of these results is discussed in the context of intraguild interactions.

Investigations on Raphidopalpa foveicollis (Lucas) in an organic cultivation of winter melon in western Sicily Red pumpkin beetle (Raphidopalpa foveicollis), is a Chrysomelidae beetle that lives on various species of cucurbits with greater preference for Cucumis sp. Both larval and adult stages are injurious to the crops. The former feeds on roots and stems of the plants, while the latter feeds on foliage, petals and fruits. In Sicily, this insect has occurred in the past as a secondary pest on the winter melon, but sometimes it reaches levels of infestation to arouse considerable concern among farmers. In order to implement economic methods of pest control a study on organic cultivation of winter melon was conducted in Camporeale (500 meters a.s.l.) (Palermo). Particularly, the dynamics of population and infestation levels have been investigated, taking into account also the possible influence of mulching, using chromotropic traps. Such traps consisted of yellow adhesive plates placed horizontally in mulched rows, on the plastic film, and between the rows, on the ground. In addition, surveys were carried out by comparing mulched plots and not mulched ones. Results showed that the peak catches (47.4 adults / trap) occurred in mid-June and the greater number of catches was found in the traps placed between the rows, with significant difference. A greater number of individuals has been detected on plants of the not mulched plots than that of the mulched plots, even though no statistically significant difference was found. The percentage of plants with damaged leaves ranged from 68.7% to 100% on mulched plots and 93.3% to 100% on not mulched plots with no significant differences. The presence of adults has also been observed on fruits but without signs of trophic activity. In addition, young stages were not detected in the plants examined. In conclusion, the combined effect of mulching, at least until the vegetation does not cover the plastic film, and sticky traps, placed mostly between the rows, plays a synergistic action to the pest control. Considering the low cost of such technique, it may be a potential tool for managing this pest using mass trapping method.

Since their discovery, many semiochemicals (behavior modifying chemicals) have been identified and synthetized, and a number of techniques have been developed to use them in integrated pest management (IPM) programs against insect pests. In particular, the uses of semiochemicals in IPM to monitor insect pest populations and to interfere with their behavior preventing agricultural damage are widely adopted by the growers. In the same time, evidences that semiochemicals can also modify the behavior of insect natural enemies inspired researchers to explore the possibility to use semiochemicals to conserve and/or enhance the efficacy of natural enemies in cropping systems. However the use of semiochemicals integrated with natural enemies in IPM is still limited despite the fact that scientists have made important advances in recent years to elucidate semiochemical-natural enemies interactions in multitrophic contexts. Here we provide an overview of the IPM strategies integrating semiochemicals and natural enemies; furthermore, the factors that could be considered for more widely adoption of these strategies are discussed.

Intraguild interactions between two egg parasitoids, Trissolcus basalis (Wollaston) and Ooencyrtus telenomicida (Vassiliev) exploring egg masses of the Southern Green Stink Bug Nezara viridula (L.) were investigated in field and semi-field conditions. Field trials were conducted in tomato fields by using sentinel and naturally laid egg masses in 2010 and 2011. Egg parasitoids monitoring, by sentinel egg masses placed weekly on plants during the tomato growing season and recollected one week later, showed that T. basalis occurs from June to October, whereas O. telenomicida occurs mainly in July and August. In the same fields, collections of naturally laid egg masses display different types of parasitized egg masses: only by T. basalis, only by O. telenomicida and by both species. The outcomes showed that T. basalis achieves a higher impact on the host population than O. telenomicida, even when multiparasitism occurs. Semi-field trials were conducted from July to September 2011, using pepper plants covered with mesh net in order to create small cages with five plants inside. In each cage, egg masses were placed on four plants located near to the cage corners and then T. basalis and O. telenomicida were released individually or simultaneously on the central plants. Egg masses were recollected after one week. The results showed that T. basalis achieves a high parasitization level when released alone but suffers competition by O. telenomicida when both species were simultaneously released.

Climate changing is a real phenomenon and the last decade was the warmest decade ever. The impact of climate change on animal communities is complex, affecting species interactions in all trophic levels, in different ways and in different bio-geographic zones. Here we will discuss about the possible effects of climate changes in shaping the competition between egg parasitoid species to consume the same hosts. Egg parasitoids are important biological control agents due to their ability to kill the pest before the crop-feeding stages emerge. Competitive effects can be divided in “extrinsic competition”, the indirect interactions between adult females searching for hosts, and “intrinsic competition”, the competition that occurs between larvae developing in the same host. The climate change impact will be addressed taking into account: 1) how quantitative and qualitative variation in plant volatile organic compound (VOC) emission may affect extrinsic competition; 2) how changes in host’s biology may affect intrinsic competition as consequence of global warming. Finally data on intraguild interactions under global warming scenario between two sympatric egg parasitoids of a true bug will be presented.

Investigations on the aphid infestation occurring on winter melon crops (Cucumis melo var. Helios) in organic farms of western Sicily The winter melon (Cucumis melo L.) is an important crop in Sicily. Previous studies carried out in western Sicily have shown that the aphid species Aphis gossipii is the key pest of winter melon crops.A. gossypii is a cosmopolitan species with very polyphagous habits; this phytophagous insect is capable of serious economic damage due to direct feeding of the sap plant and due to the honeydew secretion and the consequent presence of sooty mold and due to the possible transmission of viruses. The aim of this work was to investigate the levels of aphid infestation in two different organic winter melon fields located in western Sicily by monitoring the dynamic of population of A. gossypii and the complex of natural enemies associated with the pest. In addition the possible influence of mulching as aphid repellent has been evaluated. In one location we monitored the aphid infestation through direct observation of the plants that have been carried out weekly from transplant to harvest of the product. In the other location, we investigated the dynamics of population and levels of adult infestation, evaluating also the possible influence of mulching, using chromotropic traps, consisting in yellow adhesive plates placed horizontally in mulched rows, on the plastic film, and alleyways, on the ground. In addition, surveys were carried out by comparing mulched plots and not mulched plots. Our results showed that, in both locations, the population density of A. gossypii was low and no serious damage has been inflicted to the crop: this is probably related to the abundant presence of natural enemies of the pest and to the repellent action of mulching.

Investigations on Henosepilachna elaterii (Rossi) and Raphidopalpa foveicollis (Lucas) in an organic cultivation of winter melon in western Sicily. A study on H. elaterii and R. Foveicollis, serious pests of winter melon, was conducted in two organic melon fields of the western Sicily. Dynamics of population and infestation levels were investigated. In addition, the possible influence of mulching on R. Foveicollis infestation has been taken into account. Our results showed that H. elaterii occurred only in one field from the beginning of June and it infested 60% of the plants in the mid-July, then the pest population density dropped to about 10%. R. foveicollis occurred in both locations from the beginning of June and reached high levels of population density around the mid-June; then the pest density rapidly decreased in the two following weeks. Adults were found in the traps and the peak catches occurred in mid-June. A greater number of catches was found in the traps placed between the rows and the greater number of individuals has been detected on plants of the not mulched plots. The percentage of plants with damaged leaves ranged from 68.7% to 100% on mulched plots and 93.3% to 100% on not mulched plots. In conclusion, the damages inflicted by R. foveicollis are counterbalanced by the rapid growing rate of the plant occurring during June. Hence, this pest may cause serious injuries only in case of heavy infestation on winter melon seedlings. Similarly, the damage caused by H. elaterii is usually not heavy even if presence of high levels of infestation.

Responses of macropterous females of the ectoparasitoid Melittobia digitata Dahms (Hymenoptera: Eulophidae) to direct and indirect cues emitted by its natural hosts as well as laboratory hosts were investigated using a Y-tube olfactometer. To locate the nest ofmud dauber wasps, Trypoxylon politum Say (Hymenoptera: Crabronidae), and one of their inquilines, Anthrax spec., parasitoids exploit volatiles from the freshly built nest mud and the empty cocoon constructed by the wasps, as well as their meconium. However, the parasitoids did not respond to odors emitted by older nest mud or by the host stages that are attacked (T. politum prepupae and Anthrax spec. larvae). Melittobia digitata was not attracted to direct volatiles released by the dipteran hosts Anastrepha ludens Loew (Diptera: Tephritidae) (a natural host) and Sarcophaga bullata (Parker) (Diptera: Sarcophagidae) (a laboratory host). Based on our results, we suggest that M. digitata adopts a ‘sit and wait’ strategy to locate mud dauber wasps, relying mainly on indirect host-related cues: females search for nests that are under construction and once found, they wait inside the cell until the host completes its cocoon and releases meconium, an indicator that is associated with host suitability. No attraction was found to dipteran hosts, suggesting that parasitization of these hosts may be incidental, due to the broad host plasticity of Melittobia wasps.

Study on the parasitoid complex of Prays oleae (Bernard) and parasitism levels in an organic olive orchard in western Sicily (Italy). Prays oleae is a serious pest of the olive tree in the Mediterranean basin. This phytophagous infests fruits (carpophagous generation) and leaves (phyllophagous generation). In cases of high population densities crop losses, caused mainly by fruit drop, may be heavy. The aim of this work was to investigate on 1) parasitoid species living on P. oleae, 2) their incidence parasitoid complex, 3) parasitism levels and 4)the influence on the fruit fall. Observations were conducted in an organic olive grove near Contessa Entellina (PA) (Sicily, Italy) (37.43.44 N; 13.10.14 E, 640 m s. l. m.). Samples of leaves, weekly, were collected, during the overwintered (phyllophagous) and March 2004 to July 2007. In laboratory, singly into vials and observed daily until the adult emergence.

In this study the responses of females of the egg parasitoid Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae) to volatile and contact chemicals from its host Nezara viridula (L.) (Heteroptera: Pentatomidae) and from host plant Solanum lycopersicum L. were investigated in a Y-tube olfactometer and in open arena. Our results in the Y-tube olfactometer tests showed that: (1) female wasps were attracted to volatiles from adult host virgin male and to volatiles from a host mated female, showing a clear preference for the volatiles emitted from the former; volatiles from host virgin females did not attract O. telenomicida females; (2) only volatiles produced by host-damaged plant complex were attractive to wasp females, while volatiles from undamaged, damaged or egg carrying damaged tomato plants were not. In open arena tests, O. telenomicida females did not respond to chemical traces left by N. viridula adults in the different sexes and/or physiological conditions. The behavioral implications of these results are discussed matching up to different strategies adopted by the egg parasitoid Trissolcus basalis and focusing on possible intraguild interactions between these two parasitoid species which in field can share the same N. viridula egg masses.

Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae) è un parassitoide oofago di Nezara viridula (L.) (Heteroptera: Pentatomidae) di origine paleartica frequentemente diffuso in Sicilia. Scopo del presente lavoro è stato quello di investigare il processo di localizzazione dell’ospite nel sistema tritrofico Solanum lycopersicum L. – N. viridula – O. telenomicida. In particolare sono stati condotti esperimenti in olfattometro a Y, per valutare il ruolo attrattivo dei composti volatili emessi sia dalle piante, sia dagli adulti della cimice verde, e in arena aperta, per biosaggiare. la risposta delle femmine del parassitoide alle tracce lasciate sul substrato dagli adulti di N. viridula. Le prove in olfattometro hanno mostrato che le femmine di O. telenomicida sono attratte dai semiochimici emessi dai maschi vergini e dalle femmine pre-ovideponenti del fitofago, ma non dai composti organici volatili emessi dalle piante non attaccate, né dai sinomoni prodotti dalle piante a seguito di attività di nutrizione e di ovideposizione del fitofago. Infine, nei biosaggi in arena aperta le femmine del parassitoide non hanno mostrato comportamento di ricerca motivata indotta da cairomoni di contatto deposti dagli adulti di N. viridula in movimento. Alla luce di questi risultati si può ipotizzare che il feromone di aggregazione emesso dai maschi di N. viridula possa essere il principale semiochimico utilizzato dalle femmine di O. telenomicida per la localizzazione delle uova ospiti, come già evidenziato in altre specie del genere Ooencyrtus, quali O. nezare Ishii che è risultato attratto dal feromone di aggregazione di Riptortus clavatus (Thunberg) e O. pityocampae (Mercet) che viene attratto dal feromone sessuale di Traumatocampa pityocampa (Denis & Schiffermüller).La strategia di localizzazione dell’ospite da parte di O. telenomicida viene, infine, discussa confrontandola con quella dell’imenottero scelionide Trissolcus basalis (Wollaston), un altro parassitoide della cimice verde che, in campo, è stato ritrovato coesistere con O. telenomicida sulle ovature dell’ospite. Ulteriori studi sono in corso per studiare le interazioni che si istaurano tra individui delle due specie quando questi competono per la stessa ovatura (Intra guild interaction).

Insect parasitoids are under selection pressure to optimize their host location strategy in order to maximize fitness. In parasitoid species that develop on host eggs, one of these strategies consists in the exploitation of oviposition-induced plant volatiles (OIPVs), specific blends of volatile organic compounds released by plants in response to egg deposition by herbivorous insects. Plants can recognize insect oviposition via elicitors that trigger OIPVs, but very few elicitors have been characterized so far. In particular, the source and the nature of the elicitor responsible of egg parasitoid recruitment in the case of plants induced with oviposition by stink bugs are still unknown. In this paper, we conducted behavioral and molecular investigations to localize the source of the elicitor that attracts egg parasitoids and elucidate the role of host mating in elicitation of plant responses. We used as organism study model a tritrophic system consisting of the egg parasitoid Trissolcus basalis, the stink bug host Nezara viridula and the plant Vicia faba. We found that egg parasitoid attraction to plant volatiles is triggered by extracts coming from the dilated portion of the stink bug spermathecal complex. However, attraction only occurs if extracts are obtained from mated females but not from virgin ones. Egg parasitoid attraction was not observed when extracts coming from the accessory glands (mesadene and ectadene) of male hosts were applied, either alone or in combination to plants. SDS-PAGE electrophoresis correlated with olfactometer observations as the protein profile of the dilated portion of the spermathecal complex was affected by the stink bug mating status suggesting post-copulatory physiological changes in this reproductive structure. This study contributed to better understanding the host location process by egg parasitoids and laid the basis for the chemical characterization of the elicitor responsible for OIPV emission.

The venom gland is a ubiquitous organ in Hymenoptera. In insect parasitoids, the venom gland has been shown to have multiple functions including regulation of host immune response, host paralysis, host castration and developmental alteration. However, the role played by the venom gland has been mainly studied in parasitoids developing in larval or pupal hosts while little is known for parasitoids developing in insect eggs. We conducted the first extensive characterization of the venom of the endoparasitoid Ooencyrtus telenomicida (Vassiliev), a species that develops in eggs of the stink bug Nezara viridula (L.). In particular we investigated the structure of the venom apparatus, its functional role and conducted a transcriptomic analysis of the venom gland. We found that injection of O. telenomicida venom induces: 1) a melanized-like process in N. viridula host eggs (host-parasitoid interaction), 2) impairment of the larval development of the competitor Trissolcus basalis (Wollaston) (parasitoid-parasitoid interaction). The O. telenomicida venom gland transcriptome reveals a majority of digestive enzymes (peptidases and glycosylases) and oxidoreductases (laccases) among the most expressed genes. The former enzymes are likely to be involved in degradation of the host resources for the specific benefit of the O. telenomicida offspring. In turn, alteration of host resources caused by these enzymes may negatively affect the larval development of the competitor T. basalis. We hypothesize that the melanization process induced by venom injection could be related to the presence of laccases, which are multicopper oxidases that belong to the phenoloxidases group. This work contributed to a better understanding of the venom in insect parasitoids and allowed to identify candidate genes whose functional role can be investigated in future studies.

International audience; Research on interspecific competitive interactions among insect parasitoids has often been characterized by laboratory studies in which host insects are exposed to female parasitoids of different species in various sequences and combinations. In the last years, an increasing number of studies have investigated interspecific interactions under field and semi-field conditions although just a few number of works focused on egg parasitoids. In this work, we undertook a two-year study to investigate interspecific interactions between Trissolcus basalis (Wollaston) (Hymenoptera: Platygastridae) and Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae), two egg parasitoids of the pest Nezara viridula (L.) (Heteroptera: Pentatomidae) that co-occur in cultivated crops. Under semi-field (in out-door mesh cages) and field conditions, we investigated: 1) the seasonal occurrence of competing parasitoid species on sentinel egg masses; 2) the impact achieved by competing species on the shared host on naturally laid egg masses; 3) the outcome of intraguild interactions under controlled conditions. Results from sentinel egg masses showed that T. basalis occurs in May and successfully parasitizes hosts until the end of September/beginning of October, whereas O. telenomicida is mainly occurring in July-August. In both years, it was found that T. basalis is predominant. From naturally laid egg masses, results indicated that T. basalis achieves higher impact on the hosts, even in those egg masses which are parasitized by more than one female of different species (= multiparasitism). Results from manipulating intraguild interactions showed that T. basalis achieves higher impact on N. viridula when released alone, but it suffers from competition with O. telenomicida. The ecological factors that play a role in intraguild interactions in the context of biological control perspective are discussed.