PATCH TIME ALLOCATION BY THE EGGPARASITOID TRISSOLCUS BASALIS ON OF HOST FOOTPRINTS

Chemical Ecology of Insect Parasitoids: Essential Elements for Developing Effective Biological Control Programmes

Insect parasitoids can find their hosts in complex environments and reproduce through a series of behavioural steps which are regulated mainly by chemical cues, termed semiochemicals. According to functional criteria, stimuli can be classified into four main categories: (A) cues coming from the habitat, the host microhabitat or the food plant, (B) direct host‐related cues, (C) indirect host‐related cues, and (D) cues coming from the parasitoid itself. In recent years, considerable progress has been made in elucidating the semiochemicals used by parasitoids to locate their hosts. Several studies provided interesting prospective for manipulating foraging behaviour of parasitoids in order to i…

Fitness costs of intrinsic competition in two egg parasitoids of a true bug

Intrinsic competition in insect parasitoids occurs when supernumerary larvae develop in the same host as consequence of multiple ovipositions by females of the same species (intra-specific competition) or by females of different species (inter-specific competition). Studies on intrinsic competition have mainly focused on understanding the factors that play a role in the outcome of competition, while fitness-related effects for the parasitoid surviving the competition have been poorly investigated, especially in egg parasitoids. Interestingly, even the winning parasitoid can experience fitness costs due to larval development in a host in which multiple factors have been injected by the ovipo…

Viruses, Fungi and Insect Pests Affecting Caper

Intraguild interactions between two egg parasitoids exploring host patches

Intraguild interactions between two egg parasitoids, Trissolcus basalis (Hymenoptera: Scelionidae) and Ooencyrtus telenomicida (Hymenoptera: Encyrtidae), exploring egg masses of the Southern Green Stink Bug (SGSB) Nezara viridula (Heteroptera: Pentatomidae), were investigated in laboratory conditions by single, simultaneous and sequential host attack experiments. Mortality of N. viridula eggs was higher in simultaneous and sequential releases compared to single species releases. In simultaneous host exploitations, T. basalis females displayed an aggressive behavior against O. telenomicida females. The outcome of multiparasitism showed that interspecific larval competition was dominated by O…

LINEAMENTI DI ENTOMOLOGIA IN AGRICOLTURA BIOLOGICA

Il libro di testo Lineamenti di Entomologia in Agricoltura Biologica vuole essere un sussidio, un filo conduttore, nell’introduzione allo studio dell’entomologia agraria, con un occhio di riguardo alle problematiche riscontrabili nelle produzioni in regime di agricoltura biologica. Il testo, infatti, presenta le caratteristiche per fornire un valido supporto didattico agli studenti iscritti ai corsi di studio delle lauree in Scienze e Tecnologie Agrarie, Agroalimentari e Forestali, che affrontano insegnamenti di entomologia agraria. Non di meno, l’attenzione posta ad approfondire aspetti relativi ai mezzi e ai metodi di controllo può renderlo uno strumento valido anche per gli studenti che …

Nectar-Inhabiting Bacteria Affect Olfactory Responses of an Insect Parasitoid by Altering Nectar Odors

AbstractFloral 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 buckwhe…

Potential effects of Bacillus thuringiensis against adults and older larvae of Rhynchophorus ferrugineus.

Stato fisiologico delle femmine del Punteruolo rosso delle palme ottenute dal monitoraggio e dalla cattura massale

Genetic variation in the behavioural mechanisms involved in the response of the egg parasitoid Trissolcus brochymenae to contact chemical cues left by the pest Murgantia histrionica

International audience; 1. The ability of parasitoid females to perceive chemical traces left by theirhosts is of utmost importance in the host location process. The behaviours involved insuch ability have thus most likely been promoted by natural selection in the course ofthe evolutionary time. For this to happen, however, there must be signicant geneticvariation in natural populations on which natural selection could act.2. Using the isofemale line method and motion analysis, we detected signicantintra-population genetic variation for several walking behaviour traits of the eggparasitoid Trissolcus brochymenae (Hymenoptera: Scelionidae) females responding tochemical traces left by its h…

Chemical analysis of residues left by walking adults of Nezara viridula which induce arrestment behavior in the egg parasitoid Trissolcus basalis.

Chemical residues deposited by walking adults of the southern green stink bug (SGSB), Nezara viridula (L.) (Heteroptera: Pentatomidae), which play a role as contact kairomones inducing arrestment behavior in the egg parasitoid Trissolcus basalis (Wollaston), were investigated in laboratory experiments. Female wasps encountering an area contaminated by chemical residues from adult hosts showed an arrestment response characterized by prolonged periods of walking and turning, resulting in systematic return to the stimulus after encountering the treatment borders. When SGSB adults were dissected into separate body parts, extracts from legs and the dorsal laminar pronota of adult females elicite…

Plant surfaces of vegetable crops mediate interactions between chemical footprints of true bugs and their egg parasitoids.

During the host location process, egg parasitoids can eavesdrop on chemical cues released from immature and adult hosts. These indirect host-related cues are highly detectable, but of low reliability because they lead egg parasitoid females to an area where oviposition is likely to occur rather then providing wasps with direct information on the presence of eggs and their location. In the host-parasitoid associations between true bugs and their scelionid egg parasitoids, female wasps perceive the chemical residues left by host adults walking on substrates as contact kairomones, displaying a characteristic arrestment posture. In this study, we demonstrated that epicuticular waxes of leaves o…

THE RED PALM WEEVIL IN SICILY: THE INTRODUCTION AND SPREAD OF AN INVASIVE ALIEN SPECIES

The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (Coleoptera: Curculionidae), is a pest from Southeast Asia accidentally introduced into North Africa and Europe two decades ago. In Sicily, RPW was recorded for the first time in 2005, then, in few years, it established becoming the most severe pest of ornamental palm species in urban, monumental and country areas. In this paper, we first report the history of its introduction and spread. Then, we reviewed the preventative and curative strategies that have been implemented with variable degrees of success in containing the invasive alien pest. Finally, we focus on the development of new strategies to detect early infestations and …

Kairomone involvement in the host specificity of the egg parasitoid Trissolcus basalis

This paper reports the results of a comparative laboratory analysis of the behavioural responses of the egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) to semiochemical cues from four species of pentatomid bugs, Nezara viridula (L.), Eurydema ventrale Klt., Murgantia histrionica Hahn. and Graphosoma semipunctatum F. (Heteroptera: Pentatomidae). In a Y-tube olfactometer, T. basalis was attracted by volatile chemicals from N. viridula, but not from other pentatomid species. In an open arena, the parasitoid reacted to chemical trails left on filter paper by all the species but most intensely to those left by N. viridula. However, upon encountering pentatomid eggs, T. b…

Pseudococcidae and Monophlebidae

The families Pseudococcidae (mealybugs) and Monophlebidae include small scale insects (Coccoidea: Hemiptera) that suck out plant sap. The bodies of young instars and adult females are covered with a wax secretion, whereas adult males carry a pair of small wings. Feeding by these pests can cause premature leaf, flower, and fruit drop, reduce plant vigour and discolour tissues. In addition, they secrete honeydew upon which sooty-mould fungi grow, reducing photosynthesis and the market value of the product. Six species of Pseudococcidae, namely Planococcus citri (Risso), Pseudococcus cryptus Hempel, Ps. longispinus (Targioni Tozzetti), Ps. calceolariae (Maskell), Ps. viburni (Signoret) and Nip…

A fine tuned strategy by Trissolcus Brochymaenae (Hymenoptera: Scelionidae) to eploit chemical traces left by Murgantia histrionica (Heteroptera:Pentatomidae)

The invasive stink bug Halyomorpha halys affects the reproductive success and the experience-mediated behavioural responses of the egg parasitoid Trissolcus basalis

Invasive species, because of their lack of co-evolutionary history with recipient communities, can act as “evolutionary traps” causing disconnects between natural enemy behavioural responses and the suitability of the invasive species as a prey/host resource. Invasion of exotic species in non-native environments may have several ecological effects, including consequences for the experience-mediated behavioural responses of indigenous foragers. Experience is usually thought to help resident species to buffer against negative impacts of new invasive species, including escaping from evolutionary traps. Here we hypothesized that the impact of foraging experience depends on whether an indigenous…

Plant surface mediates interaction between true bug chemical footprints and scelionid egg parasitoids

Chemical footprints left behind by true bugs act as contact kairomones inducing an arrestment response in scelionid egg parasitoids. Once in contact with contaminated substrates, female wasps display a characteristic arrestment posture followed by an increase of the host searching time. Previous studies were conducted on artificial substrates as filter papers, so that little is known about the effects of natural substrates on behavioural response by wasps. In field, the substrate where these interactions occur, i.e. the surface of plants, is covered by wax layers that can have a role in trophic interactions between insects. In this study, we investigated the influence of plant surfaces on a…

Mating Status of an Herbivorous Stink Bug Female Affects the Emission of Oviposition-Induced Plant Volatiles Exploited by an Egg Parasitoid

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 …

Impact of heteroptera pentatomidae feeding and oviposition on photosynthesis of herbaceous plants and egg parasitoids host location

The present study was designed to examine the effect of heteroptera pentatomidae feeding and/or oviposition on photosynthesis. Murgantia histrionica and Nezara viridula were fed on Brassica and Phaseolus plants, respectively. The changes in photosynthetic gas exchange and chlorophyll fluorescence parameters were followed immediately after the feeding as well as during the post-feeding period (24, 48 and 72 h). Murgantia feeding caused visible damage on leaf lamina, whereas this was not the case with Nezara feeding. In both cases a substantial decrease (50%) in photosynthesis was observed, which was partially restored only in Phaseolus plants by the end of the experiment. By using high resol…

Learning can be detrimental for a parasitic wasp

Animals have evolved the capacity to learn, and the conventional view is that learning allows individuals to improve foraging decisions. The parasitoid Telenomus podisi has been shown to parasitize eggs of the exotic stink bug Halyomorpha halys at the same rate as eggs of its coevolved host, Podisus maculiventris, but the parasitoid cannot complete its development in the exotic species. We hypothesized that T. podisi learns to exploit cues from this non-coevolved species, thereby increasing unsuccessful parasitism rates. We conducted bioassays to compare the responses of naïve vs. experienced parasitoids on chemical footprints left by one of the two host species. Both naïve and experienced …

Gli insetti fitofagi degli agrumi

Climate change impact on extrinsic and intrinsic competition between egg parasitoids

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 compet…

How can two competing egg parasitoid species coexist in a host patch?

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…

Volatile unsaturated hydrocarbons emitted by seedlings of Brassica species provide host location cues to Bagrada hilaris

Bagrada hilaris Burmeister, is a stink bug native to Asia and Africa and invasive in the United States, Mexico, and more recently, South America. This species can cause serious damage to various vegetable crops in the genus Brassica, with seedlings being particularly susceptible to B. hilaris feeding activity. In this study, the role of volatile organic compounds (VOCs) emitted by seedlings of three Brassica species on the host preference of B. hilaris was evaluated. In dual choice arena and olfactometer bioassays, adult painted bugs preferred B. oleracea var. botrytis and B. napus over B. carinata. Volatiles from B. oleracea seedlings were collected and bioassayed with B. hilaris adults an…

Insect oviposition induces volatile emission in herbaceous plants that attracts egg parasitoid

SUMMARYThe egg parasitoid Trissolcus basalis (Wollaston) (Hymenoptera:Scelionidae) responded to synomones emitted by leguminous plants induced by feeding and oviposition activity of the bug Nezara viridula (L.)(Heteroptera: Pentatomidae). This was shown by laboratory bioassays using a Y-tube olfactometer. Broad bean leaves (Vicia faba L.) damaged by feeding activity of N. viridula and on which host egg mass had been laid produced synomones that attracted T. basalis. By contrast,undamaged leaves or feeding-damaged leaves without eggs did not attract wasp females. French bean plants (Phaseolus vulgaris L.) also emitted attractive synomones when they were damaged by host feeding and carrying e…

OSSERVAZIONI BIOLOGICHE SU PHYLLONORYCTER DELITELLA (DUPONCHEL) (LEPIDOPTERA: GRACILLARIIDAE) IN LABORATORIO

A sex pheromone triggers courtship behaviour in the egg parasitoid Trissolcus brochymenae

Evaluation of Brassicaceae seedlings as trap plants for Bagrada hilaris Burmeister in Caper bush cultivations

The caper bush, Capparis spinosa (Brassicales: Capparaceae), is intensively grown on Pantelleria Island (Trapani, Sicily, Sicilian channel) where it has been granted protected geographical indication (PGI) by the EU. On this island, Bagrada hilaris, a stink bug native of Asia and Africa, is the major pest of caper crops. Recent studies have shown the attraction of B. hilaris to volatiles of brassicaceous plants at the seedling stage. The objective of this study was to evaluate three cotyledon-stage seedlings of host plants, Brassica oleracea var. botrytis (cauliflower), Eruca sativa (rocket) and Brassica carinata (Abyssinian cabbage), as potential trap plants for B. hilaris. The relative pr…

Laboratory and field studies to test the attractiveness of the Red Palm Weevil to synthetic palm esters

Ritrovamento di Paysandisia archon (Lepidoptera, Castniidae) in Sicilia

The Role of (E)-2-octenyl Acetate as a Pheromone of Bagrada hilaris (Burmeister): Laboratory and Field Evaluation

The pentatomid bug Bagrada hilaris is a key pest of brassicaceous crops in several areas of the world. Previous studies suggest that mate location of this species is mediated by volatile chemicals produced by males, among which the main compound is (E)-2-octenyl acetate. However, the possible attraction of males, females, and nymphs to this compound has not yet been specifically tested. In this study, we tested the response of B. hilaris females, males, and nymphs to (E)-2-octenyl acetate using an electroantennogram (EAG) and olfactometer in the presence or absence of a host plant. Moreover, (E)-2-octenyl acetate as an attractant lure in field trap bioassays was evaluated. EAG recordings sh…

Influence of Feeding and Oviposition by Phytophagous Pentatomids on Photosynthesis of Herbaceous Plants

Abstract Feeding by herbivorous insects may change photosynthetic activity of host plants. We studied how feeding and oviposition by herbivorous stink bugs, Murgantia histrionica and Nezara viridula (Heteroptera: Pentatomidae), affect photosynthetic parameters of Brassica oleracea (savoy cabbage) and Phaseolus vulgaris (French bean). First, we measured photosynthetic gas exchange, chlorophyll fluorescence imaging, and emission of induced volatile organic compounds (VOC) immediately after feeding and during a post-feeding period. Photosynthesis decreased rapidly and substantially in B. oleracea and P. vulgaris infested by feeding bugs. Stomatal conductance did not decrease proportionally wit…

Sex pheromone compounds mediating host specificity in the egg parasitoid Telenomus busseolae Gahan.

Impiego di tecniche elettroantennografiche per lo studio dei composti semiochimici attivi nei confronti del Punteruolo rosso delle palme.

Il ruolo degli idrocarburi della cuticola nelle relazioni insetto fitofago-parassitoide oofago.

Egg parasitoid attraction toward induced plant volatiles is disrupted by a non-host herbivore attacking above or belowground plant organs.

Plants respond to insect oviposition by emission of oviposition-induced plant volatiles (OIPVs) which can recruit egg parasitoids of the attacking herbivore. To date, studies demonstrating egg parasitoid attraction to OIPVs have been carried out in tritrophic systems consisting of one species each of plant, herbivore host, and the associated egg parasitoid. Less attention has been given to plants experiencing multiple attacks by host and non-host herbivores that potentially could interfere with the recruitment of egg parasitoids as a result of modifications to the OIPV blend. Egg parasitoid attraction could also be influenced by the temporal dynamics of multiple infestations, when the same …

Individuazione di un feromone sessuale marcante traccia nell’imenottero parassitoide Metaphycus luteolus

Metaphycus luteolus Timberlake (Hymenoptera: Encyrtidae) è un parassitoide gregario facolativo di Coccidi (Homoptera: Coccidae). Nel presente studio, si è indagato sull’esistenza in questa specie di un feromone che potesse guidare l’incontro fra i sessi nei siti di emergenza. In altri imenotteri calcidoidei, parassitoidi di ospiti che vivono in dense aggregazioni come colonie di cocciniglie o afidi, l’incontro fra i sessi nei siti di emergenza è mediato da feromoni a corto raggio. Il presente studio mette in evidenza l’esistenza di un feromone di traccia in M. luteolus. I biosaggi sono stati eseguiti con l’ausilio di un’arena aperta, costituita da una piastra di vetro, sulla quale sono stat…

I batteri associati al nettare fiorale influiscono sulle longevità degli insetti parassitoidi

I parassitoidi adulti frequentemente visitano le piante in fioritura, ricercando nettare fiorale per coprire i loro bisogni energetici e nutrizionali. In letteratura, infatti, i benefici del nettare sulla fitness dei parassitoidi sono ampiamente documentati. Sebbene il nettare fiorale costituisca un substrato ideale per la crescita di comunità microbiche che possono alterarne le caratteristiche organolettiche, l'effetto della fermentazione batterica del nettare sui parassitoidi non è stato ancora sufficientemente esplorato. In questo lavoro è stata studiata la longevità dei parassitoidi adulti utilizzando nettare sintetico fermentato da diversi ceppi batterici appartenenti ai phyla Firmicut…

Responses of Rhynchophorus ferrugineus adults to selected synthetic palm esters: electroantennographic studies and trap catches in an urban environment

BACKGROUND: The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier, accidentally introduced into the European countries facing the Mediterranean basin, is becoming the most serious pest for ornamental palms in the urban environment. In the present work, tests were conducted on the electroantennogram (EAG) and behavioural responses of RPW adults to five selected synthetic palm esters, ethyl propionate, ethyl butyrate, ethyl isobutyrate, ethyl lactate and ethyl acetate, to assess the application of a mass trapping technique in an urban environment. RESULTS: In the laboratory, EAG bioassays on RPW adults with the synthetic palm esters showed: (1) positive dose-dependent responses; (2) di…

Egg parasitoid exploitation of plant volatiles induced by single or concurrent attack of a zoophytophagous predator and an invasive phytophagous pest

AbstractZoophytophagous insect predators can induce physiological responses in plants by activating defence signalling pathways, but whether plants can respond to facultative phytophagy by recruiting natural enemies remains to be investigated. In Y-tube olfactometer bioassays, using a system including a Vicia faba plant, the zoophytophagous predator Podisus maculiventris and the egg parasitoid Telenomus podisi, we first demonstrated that T. podisi females are attracted by broad bean plants damaged by feeding activity of P. maculiventris and on which host egg masses had been laid, while they are not attracted by undamaged plants or plants damaged by feeding activity alone. In a second experi…

Host kairomone learning and foraging success in an egg parasitoid: a simulation model

Trissolcus basalis (Wollaston) (Hymenoptera: Scelionidae) is an egg parasitoid that recognises chemical residues left by its host the green stink bug Nezara viridula (L.) (Heteroptera: Pentatomidae) as kairomone signals, enabling it to find egg masses in which to lay eggs. 2. Kairomones are usually present as patches deposited by N. viridula females, and recent results (Peri et al. , Journal of Experimental Biology , 209 , 3629 - 3635, 2006) indicated that females of T. basalis are able to learn the features of their foraging environment and to adjust accordingly the amount of time spent on the patches of kairomones they are visiting, depending on whether or not host eggs are found. 3. In o…

Identification of Brassicadiene, a Diterpene Hydrocarbon Attractive to the Invasive Stink Bug Bagrada hilaris, from Volatiles of Cauliflower Seedlings, Brassica oleracea var. botrytis

Brassicadiene, a novel tricyclic diterpene hydrocarbon, was identified by a combination of mass spectrometry, microchemical tests, and analysis of NMR spectra. The compound constitutes >90% of the volatile organic compounds produced by cauliflower seedlings, Brassica oleracea var. botrytis. The invasive stink bug Bagrada hilaris is strongly attracted to brassicadiene, providing a mechanism for this herbivore, which specializes on cruciferous plants, to locate its hosts in a nutrient-rich and vulnerable stage.

La cattura massale degli adulti del Punteruolo rosso nel comune di Marsala

Influence of host footprints kairomone and past oviposition experience on the host location behaviour of Trissolcus basalis

The ovipositing female of Ooencyrtus telenomicida relies on physiological mechanisms to mediate intrinsic competition with Trissolcus basalis

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 mechan…

Chemical Composition and Evaluation of Insecticidal Activity of Calendula incana subsp. maritima and Laserpitium siler subsp. siculum Essential Oils against Stored Products Pests

The problems of the environment and human health related to the use of synthetic and broad-spectrum insecticides have increasingly motivated scientific research on different alternatives and among these, the use of green systems, such as essential oils, have been explored. Several species of the Apiaceae and Asteraceae families, aromatic herbs rich in secondary bioactive metabolites, are used in the industrial field for pharmaceutical, cosmetic, and food purposes. Different essential oils extracted from some species of these families have shown acute toxicity and attractive and/or repellent effects towards different insects. In our work, we investigated the toxic potential of Calendula inca…

A comparative study of viral infectivity, accumulation and symptoms induced by broad bean wilt virus 1 isolates

Broad bean wilt virus 1 (BBWV-1, genus Fabavirus, family Secoviridae) is a bipartite positive-sense single-stranded RNA virus distributed worldwide infecting many herbaceous species. Until now, scarce information regarding biological properties of BBWV-1 isolates is available. This work shows a comparative study on virus infectivity (proportion of infected plants over inoculated plants), virus accumulation and symptoms induced by four genetically different BBWV-1 isolates (Ben, B41/99, NSRV and PV0548) which were mechanically inoculated on several herbaceous hosts. The four BBWV-1 isolates infected broad bean, tomato, pepper and Nicotiana benthamiana plants, whereas none of them infected cu…

Volatile compounds released by disturbed and undisturbed adults of Anchomenus dorsalis (Coleoptera, Carabidae, Platynini) and structure of the pygidial gland

Volatile compounds produced by adults of Anchomenus dorsalis under undisturbed and disturbed conditions were investigated with an all-glass aeration apparatus. GC-MS analysis of the crude extracts from undisturbed and disturbed adults highlighted four major volatile compounds, undecane, heneicosane, Z-9 tricosene and tricosane, of which significantly more undecane was released by disturbed adults compared to undisturbed beetles. The pygidial glands of adults of A. dorsalis were investigated using light and Transmission Electron Microscopy (TEM). Each gland showed dense aggregates of secretory cells organized into visually distinct lobes; a long collecting canal that drains the secretion tow…

Chemo-orientation responses in hymenopteran parasitoids induced by substrate-borne semiochemicals

Hymenopteran parasitoids can utilize substrate-borne semiochemicals released by conspecifics or by their hosts, increasing the likelihood of successful mating and host location. According to the literature, two substrate-borne chemo-orientation patterns can occur: (1) biased random searching, a non-directional reaction toward the chemicals (kinesis), and (2) trailfollowing searching, a directional response toward the source emitting the chemical compounds (taxis). These two different strategies can be adopted by parasitoids to locate hosts and mates. In host location, random searching is induced by allelochemicals indirectly associated with the host, whereas trail-following behavior is indu…

Effect of dual biotic stress on plant volatile synomones used by egg parasitoids

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 inv…

The behavioral responses of the egg parasitoid Ooencyrtus telenomicida to semiochemicals from first and second trophic level

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 com…

Host chemical footprints induce host sex discrimination ability in egg parasitoids

Trissolcus egg parasitoids, when perceiving the chemical footprints left on a substrate by pentatomid host bugs, adopt a motivated searching behaviour characterized by longer searching time on patches were signals are present. Once in contact with host chemical footprints, Trissolcus wasps search longer on traces left by associated hosts rather than non-associated species, and, in the former case, they search longer on traces left by females than males. Based on these evidences, we hypothesized that only associated hosts induce the ability to discriminate host sex in wasps. To test this hypothesis we investigated the ability of Trissolcus basalis, T. brochymenae, and Trissolcus sp. to disti…

Un anno di cattura massale del punteruolo rosso nei comuni di Marsala (TP) e Grottammare (AP) con informazioni sulle condizioni fisiologiche delle femmine

La tecnica della cattura massale ha lo scopo di eliminare il maggior numero possibile di individui della specie dell’insetto che si vuole combattere. Nei casi in cui l’attrattivo feromonale induca comportamenti di aggregazione, come il feromone prodotto dai maschi del Punteruolo rosso delle palme, Rhynchophorus ferrugineus (Olivier), nelle trappole vengono attirati individui di entrambi i sessi. Lo stato fisiologico delle femmine catturate influenza fortemente l’impatto della cattura massale sullo sviluppo demoecologico dell’insetto. Infatti, se le trappole catturano per lo più femmine che hanno già ovideposto il ruolo della cattura massale diviene meno apprezzabile. Nell’aprile del 2008 so…

Dinamica di popolazione di Aphis gossypii possibile vettore del Virus della Tristeza in un agrumeto della Sicilia occidentale

Tra le specie di afidi che attaccano gli agrumi in Sicilia, Aphis spiraecola Patch, Toxoptera aurantii (B.d.F) e Aphis gossypii Glover rivestono importanza economica, essendo presenti dalla primavera all’autunno con livelli di infestazione molto alti. Oltre ai danni legati all’attività trofica, tutte e tre le specie primarie, sono in grado di trasmettere il virus della Tristeza (CTV); in bibliografia l’efficienza è considerata alta nel caso di A. gossypii e poco rilevante nel caso delle altre due specie. La trasmissibilità del CTV, oltre che dalla specie vettrice, dipende da diversi fattori quali, le specie di Citrus donatrici o recettrici, la virulenza dell'isolato del virus, il comportame…

Intraguild interaction between egg parasitoids: the role of the host egg mass size and parasitoids’ reproductive capacities

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 labo…

Behaviour-modifying compounds for management of the red palm weevil (Rhynchophorus ferrugineusOliver)

BACKGROUND Populations of red palm weevil (RPW), a severe pest of palms in Mediterranean countries, might be limited by semiochemical-based behaviour-disrupting methods. We evaluated the effects of electroantennogram (EAG)-active plant volatiles on the behaviour of RPWs from Italy and Israel. In field experiments, α-pinene, citronellol, geraniol, citral and 1-octen-3-ol were tested for their ability to disrupt attraction to pheromone–kairomone and molasses baited traps. Those that were found to be disruptive in the field were evaluated in a laboratory choice bioassay in individual cages for their effect on RPW female feeding and oviposition. RESULTS Field experiments showed reduced captures…

Native egg parasitoids recorded from the invasive Halyomorpha halys successfully exploit volatiles emitted by the plant–herbivore complex

When an accidentally introduced pest establishes in the invaded area, native natural enemies may adapt to the new host. A decade after the accidental introduction of the brown marmorated stink bug, Halyomorpha halys, in Europe, two generalist native egg parasitoids, the eupelmid Anastatus bifasciatus and the encyrtid Ooencyrtus telenomicida, have been recorded from this invasive agricultural pest in the field. Both species are able to complete development to the adult stage within the new host. Trissolcus basalis (Platygastridae = Scelionidae), which is not associated with H. halys in the field, was reared from freeze-killed sentinel eggs placed on soybean plants in central Italy. We tested…

Lures for red palm weevil trapping systems: aggregation pheromone and synthetic kairomone

Background The 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. Results In general, although capture data and emission had noticeable variability among locations, significantly fewer RPW were captured in pyramidal Picusan® traps with the lowest ferrugineol emission rates tested (0.6-…

Noise effects in biological systems

Impiego di insetticidi di origine vegetale per il contenimento delle popolazioni di Bagrada hilaris nei cappereti panteschi

Bagrada hilaris, nota con il nome di Cimice delle crocifere, è un Eterottero Pentatomide dannoso al cappero nell’isola di Pantelleria. Per verificare la possibilità di utilizzare insetticidi a basso impatto ambientale per il contenimento delle popolazioni di questo fitofago, sono state condotte prove in laboratorio e in campo con due insetticidi di origine vegetale, Show e Neemik, e un insetticida di sintesi, Decis Jet, utilizzato come controllo. Nel 2004 sono state condotte prove in laboratorio atte a definire i valori di CL70 e le curve dose-risposta a diverse concentrazioni di formulato commerciale. Nel biennio 2005-06, l’efficacia degli insetticidi è stata valutata con prove in campo ef…

Asphondylia gennadii (Marchal) fitofago dannoso al cappero nelle isole minori della Sicilia (Diptera: Cecidomyiidae)

Host sex discrimination by an egg parasitoid on Brassica leaves.

Egg parasitoids are able to find their hosts by exploiting their chemical footprints as host location cues. In nature, the apolar epicuticular wax layer of plants that consists of several classes of hydrocarbons serves as the substrate that retains these contact kairomones. However, experiments on chemical footprints generally have used filter paper as substrate to study insect behavior. Here, we explored the ability of Trissolcus basalis (Scelionidae) females to discriminate between footprint cues left by male and female Nezara viridula (Pentatomidae) on leaves of their host plant Brassica oleracea (broccoli). Furthermore, we analyzed the chemical composition of the outermost wax layer of …

Biological control of invasive stink bugs: review of global state and future prospects

International audience; Invasive stink bugs (Hemiptera: Pentatomidae) are responsible for high economic losses to agricul-ture on a global scale. The most important species, dating from recent to old invasions, includeBagrada hilaris (Burmeister), Halyomorpha halys (Stal), Piezodorus guildinii (Westwood), Nezara vir-idula (L.), and Murgantia histrionica (Hahn). Bagrada hilaris, H. halys,andN. viridula are nowalmost globally distributed. Biological control of these pests faces a complex set of challenges thatmust be addressed to maintain pest populations below the economic injury level. Several case studiesof classical and conservation biological control of invasive stink bugs are reported …

Intraguild interactions between two egg parasitoids of a true bug: from laboratory to field investigations

Intraguild interactions can play a role in species coexistence and in sizing and shaping community structures. In addition, understanding how competitive interactions between parasitoid guilds can affect pest suppression may improve biological control. Interspecific competitive effects can be divided in “extrinsic competition”, the indirect interactions between adult females searching for or exploiting hosts, and “intrinsic competition”, the competition that occurs between larvae developing in the same host. In this work we performed both laboratory and field investigations to address on intraguild interactions occurring between Trissolcus basalis (Hymenoptera: Scelionidae) and Ooencyrtus t…

Assessment of synthetic chemicals for disruption of Rhynchophorus ferrugineus response to attractant-baited traps in an urban environment

The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (Coleoptera, Curculionidae), is one of the most severe pests of ornamental palm species in urban areas of Mediterranean countries. Aiming to discover inhibitory semiochemicals for RPW population management in urban environments, we conducted electroantennographic (EAG) screenings of 17 commercially available synthetic compounds, representing three groups of plant volatiles (isoprenoids, phenyl propanoid derivatives and fatty acid derivatives) known for their repellent effects toward insects. These tests were followed by trap-based screenings of EAG-active menthone, alpha-pinene and methyl salicylate, singly and in combination, und…

The role of host cuticular hydrocarbons in mediating the host searching behaviour of an egg parasitoid.

RNA2-encoded VP37 protein of Broad bean wilt virus 1 is a determinant of pathogenicity, host susceptibility, and a suppressor of post-transcriptional gene silencing

Abstract Broad bean wilt virus 1 (BBWV‐1, genus Fabavirus, family Secoviridae) is a bipartite, single‐stranded positive‐sense RNA virus infecting many horticultural and ornamental crops worldwide. RNA1 encodes proteins involved in viral replication whereas RNA2 encodes two coat proteins (the large and small coat proteins) and two putative movement proteins (MPs) of different sizes with overlapping C‐terminal regions. In this work, we determined the role played by the small putative BBWV‐1 MP (VP37) on virus pathogenicity, host specificity, and suppression of post‐transcriptional gene silencing (PTGS). We engineered a BBWV‐1 35S‐driven full‐length cDNA infectious clone corresponding to BBWV‐…

Thermal stress affects patch time allocation by preventing forgetting in a parasitoid wasp

Learning and memory allow animals to adjust their foraging strategies through experience. Despite the known impact of temperature on many aspects of the behavioral ecology of animals, memory retention in the face of realistic thermal stress has seldom been assessed. In the laboratory, we studied the behavioral expression of an egg parasitoid’s (Trissolcus basalis) memory when exposed to thermal stress that could be encountered in nature. We hypothesized that thermal stress would disrupt memory consolidation and/ or modify the optimality of memory retention, thus affecting patch time allocation strategies. Memory consolidation was resilient to 1 h of thermal stress following an unrewarded ex…

PIANTE AROMATICHE E MEDICINALI: L’ ENTOMOCENOSI DEL CAPPERO IN SICILIA

Guilds of herbivore insects of medicinal and aromatic plants are generally composed by poliphagous insects that only occasionally are present at high infestation levels. In this paper the main insect pests observed on Capper spinosa (L.) in Sicily are described. The key pests of this crop are Capparimyia savastani (Martelli) – (Diptera: Tephritidae), Asphondylia gennadii (Marchal) (Diptera: Cecidomyiidae), and, the painted bug Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae). Infestations of other insect pests are also occasionally recorded as the case of the southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae), in the island of Ustica; the cabbage butterfly, P…

Urban landscape evolution as a consequence of an invasive pest: The case of a small sicilian town

The Red Palm Weevil (RPW), after its accidental introduction in Italy in 2005, determined a progressive disruption of Canary palms mostly in the central and southern regions. As it is difficult to undertake the management of this pest, the possibility of substituting the killed/symptomatic palms with other ornamental trees has been recently discussed. In this context, understanding the citizens' needs about green areas can improve the management of public parks and urban greening. Involving citizens on the natural resource management using public participation processes is crucial. The case study of a small town of Sicily (Italy) was treated and the spread of this pest was monitored. Moreov…

First extensive characterization of the venom gland from an egg parasitoid: structure, transcriptome and functional role.

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 functio…

Interspecific extrinsic and intrinsic competitive interactions in egg parasitoids

Interspecific competitive interactions can occur either between adult parasitoids searching/exploiting hosts (extrinsic competition) or between parasitoid larvae developing within the same host (intrinsic competition). Understanding how interspecific competition between parasitoids can affect pest suppression is important for improving biological pest control. The purpose of this work was to review both extrinsic and intrinsic competition between egg parasitoid species. These are organisms that are often candidates for biological control programs due to their ability to kill the pest before the crop feeding stage. We first reviewed the literature about interspecific competitive abilities of…

Electrophysiological and behavioural responses of the housefly to “sweet” volatiles of the flowers of Caralluma europaea (Guss.) N.E. Br.

In sapromyiophilous plants, up to date, long range attraction of fly pollinators has been thoroughly investigated and attributed to ‘‘fetid’’ floral compounds, while the ‘‘sweet’’ floral scent fraction has not been spe- cifically investigated and its role has received little atten- tion. The aim of the present study was to verify if terpenoids, which are the main compounds of the floral bouquet of Caralluma europaea, play a role in the attrac- tion of its pollinator Musca domestica. Terpinolene, a- terpinene and linalool, described as the three main volatiles of the flowers of C. europaea, were evaluated in electro- physiological investigations and blends of these com- pounds as well as the…

Foraging behaviour of an egg parasitoid exploiting plant volatiles induced by pentatomids : The role of adaxial and abaxial leaf surfaces

Several phases of herbivorous insect attack including feeding and oviposition are known to induce plant defenses. Plants emit volatiles induced by herbivores to recruit insect parasitoids as an indirect defense strategy. So far, volatiles induced by herbivore walking and their putative role in the foraging behavior of egg parasitoids have not been investigated. In this paper we studied the response of the egg parasitoid Trissolcus basalis toward volatiles emitted by Vicia faba plants as consequence of the walking activity of the host Nezara viridula. Olfactometer bioassays were carried out to evaluate wasp responses to plants in which the abaxial or the adaxial surfaces were subjected to wa…

Responses of Aphytis chilensis to the synthetic sex pheromone of the Oleander scale

Outcomes of intraguild interactions between two egg parasitoids in field and semi-field conditions

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 o…

Leaf epicuticular waxes effects egg parasitoid’s response to host adult footprint contact kairomone

Chemical footprints left behind by true bugs are perceived as a contact kairomones by scelionid egg parasitoids. In the system Nezara viridula and its egg parasitoid Trissolcus basalis, previous studies have shown that the kairomone mediating such behavior is part of N. viridula’s cuticular hydrocarbons. In this study, the effect of epicuticular waxes of leaves of broad bean, Vicia faba, on wasp response to footprints of N. viridula females are investigated. Plants with intact waxes layer were used (1) without host chemical contamination, or (2) contaminated by host female footprints. Mechanically de-waxed plants were tested (3) without host chemical contamination, or (4) de-waxed a few min…

Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae), fitofago dannoso al cappero sull'isola di Pantelleria: biologia e mezzi di controllo

Host specificity in the egg parasitoid Telenomus busseolae is mediated by sex pheromone compounds

Several studies showed that egg parasitoids are able to detect host sex pheromones produced by adult hosts as a host cue. In this way female wasps are directed toward an area where host mating is in progress and where an oviposition has probably taken place or is soon to occur. Telenomus busseolae Gahan (Hymenoptera: Scelionidae) is a solitary egg parasitoid of various noctuids (Lepidoptera, Noctuidae) belonging to the genera Sesamia. In field observations, it has been demonstrated that T. busseolae reacts to the pheromone emitted by females of the corn stalk borer, Sesamia nonagrioides (Lefebvre) and the pink stem borer, Sesamia calamistis (Hampson). It is known that the sex pheromone prod…

La cattura di adulti del Punteruolo rosso delle palme con trappole a feromone e allomoni in ambiente urbano

In questo lavoro sono presentati i risultati di un anno di catture di adulti di Punteruolo rosso delle palme, Rhynchophorus ferrugineus (Olivier), con trappole a feromone e allomoni collocate nel comune di Marsala (TP). In totale sono state sistemate 47 trappole ad una distanza media di circa 200 m. Le trappole sono state innescate con feromone di aggregazione (ferrorule), acetato di etile (10 % /H2O), e melassa (10 % /H2O), ed ispezionate settimanalmente per il periodo aprile 2008 – aprile 2009. Le trappole sono state disposte lungo la costa della città(N=21), e lungo una linea che attraversa il centro cittadino (N=26). In totale sono stati catturati 4010 adulti, con un numero complessivo …

Broad bean wilt virus 1 encoded VP47 and SCP are suppressors of plant post-transcriptional gene silencing

Broad bean wilt virus 1 (BBWV-1, genus Fabavirus, family Secoviridae) is a bipartite positive single-stranded RNA (+ssRNA) virus infecting important horticultural and ornamental crops worldwide. RNA1 encodes proteins involved in virus replication, whereas RNA2 encodes the large and small coat proteins (LCP, and SCP, respectively) and two putative movement proteins with overlapping C-terminal but different sizes: 47.2 kDa (VP47) and 37 kDa (VP37). Post-transcriptional gene silencing (PTGS) is a mechanism of gene regulation and defense against pathogens such as viruses. However, most plant viruses encode proteins called viral suppressors of RNA silencing (VSRs) which able to inhibit PTGS. Pre…

A finely tuned strategy adopted by an egg parasitoid to exploit chemical traces from host adults.

SUMMARY Scelionid egg parasitoids can obtain reliable information on the presence of host eggs by discriminating host gender on the basis of chemical footprints of their co-evolved hosts, with a strong preference for the footprint left by host females. Based on the concept of dietary specialization and infochemical use in natural enemies, it could be predicted that host gender discrimination in specialist species belonging to the genus Trissolcus is further tuned to specific cues from distinctive chemical traces left by host females as a consequence of copulation and/or oviposition. To test this hypothesis we used the system Murgantia histrionica – Trissolcus brochymenae. Our results showed…

Feromoni sessuali volatili e di contatto che determinano l'accoppiamento in Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae).

Intraguild interactions between two egg parasitoids of a true bug in semi-field and field conditions.

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 para…

Gender discrimination ability of egg parasitoids towards coevoluted and non-coevoluted hosts

Effect of host kairomones and oviposition experience on the arrestment behavior of an egg parasitoid

SUMMARY Chemical residues left by walking adults of the southern green stink bug, Nezara viridula (L.) (Heteroptera: Pentatomidae) induce arrestment behavior in the egg parasitoid Trissolcus basalis (Wollaston)(Hymenoptera: Scelionidae) leading to prolonged periods of walking on contaminated areas and to systematic return to the stimulus after encountering the treatment borders. In this study, we quantified how the hierarchical value of residues from host adults and oviposition experience can influence the arrestment behavior of T. basalis females. Our results showed that:(1) female wasps perceived host residues at different hierarchical levels depending on the host gender, with a clear pre…

Behaviour-modifying compounds for management of the red palm weevil (Rhynchophorus ferrugineus Oliver).

BACKGROUND: Populations of red palm weevil (RPW), a severe pest of palms in Mediterranean countries, might be limited by semiochemical-based behaviour-disrupting methods. We evaluated the effects of electroantennogram (EAG)-active plant volatiles on the behaviour of RPWs from Italy and Israel. In field experiments, α-pinene, citronellol, geraniol, citral and 1-octen-3-ol were tested for their ability to disrupt attraction to pheromone-kairomone and molasses baited traps. Those that were found to be disruptive in the field were evaluated in a laboratory choice bioassay in individual cages for their effect on RPW female feeding and oviposition. RESULTS: Field experiments showed reduced captur…

Monitoraggio e controllo di insetti infestanti le collezioni dell’erbario dell’orto botanico di Palermo

Gli erbari sono strumenti d’importante rilevanza scientifica che conservano esempi di piante rare, endemiche o estinte, e assumono essi stessi notevole interesse come beni culturali per il loro valore storico ed estetico. Gli erbari possono essere soggetti all’attacco di diverse specie d’insetti che danneggiano le piante essiccate (exsiccata) con la loro attività di alimentazione. Il controllo di queste infestazioni è spesso aggravato dalla difficoltà di poter mettere in atto trattamenti insetticidi. In tale contesto è opportuno adoperare adeguati strumenti di monitoraggio e controllo basati su sostanze attrattive feromonali o alimentari per una corretta gestione integrata degli erbari.…

L’orientamento guidato da semiochimici di contatto in imenotteri parassitoidi

Il Chemio-orientamento negli imenotteri parassitoidi e più genericamente negli insetti, si manifesta con movimenti nel tempo e nello spazio guidati da informazioni chimiche a differente grado di volatilità. Nel caso dei semiochimici di contatto, la ricezione è affidata a sensilli gustativi uni e multiporo e si manifesta con un periodo di immobilità, durante il quale le antenne vengono mantenute aderenti alla superficie esaminata. Successivamente si possono, generalmente, distinguere due tipi di comportamento: ricerca random e ricerca direzionale. La ricerca random è caratterizzata da un decremento della velocità lineare di locomozione e da un incremento della velocità angolare, in tal modo …

Only Females Oviposit: Chemical Discrimination of Adult Stink Bug Sex by the Egg Parasitoid Trissolcus japonicus

Egg parasitoids foraging for suitable hosts scattered in the environment rely mainly on chemical cues. Elucidating the chemical ecology of natural enemies is important in the development of effective and successful strategies for conservation biological control. In this context, the host cuticular hydrocarbons, which are exploited by several species of egg parasitoids as contact kairomones, could be used to retain them by providing information about the presence and the sex of adults of the target species: sex is important because only females of the host species lay the eggs that can be subsequently utilized for parasitoid reproduction. However, the chemical basis of host sex discriminatio…

Sex pheromone and cuticular hydrocarbons of the painted bag, Bugrada hilaris (Heteroptera: Pentatomidae)

Assessment of synthetic chemicals for disruption of Rhynchophorus ferrugineus attraction

The red palm weevil (RPW), Rhynchophorus ferrugineus, Olivier (Coleoptera: Curculionidae), is currently one of the most severe pests of Canary palms in urban areas of Mediterranean countries and Date palms in cultivated areas of the Middle East. RPW aggregation pheromone can be implemented for both monitoring and mass trapping, however risks of RPW "spillover" onto palms is of great concern. Aiming to discover repellent semiochemicals for safer RPW population management, we conducted electroantennographic (EAG) screenings of 17 commercially available synthetic compounds. These compounds represent three groups of plant volatiles (isoprenoids, phenyl propanoid derivatives and fatty acid deriv…

La localizzazione dell’ospite nei parassitoidi oofagi: il ruolo delle cere epicuticolari delle piante

La localizzazione dell’ospite nei parassitoidi oofagi è il risultato di un complesso comportamento di foraggiamento influenzato prevalentemente da stimoli di natura fisica e chimica. I segnali chimici (semiochimici) possono derivare dall’interazione tra la pianta e l’uovo ospite (sinomoni indotti dall’ovideposizione), dall’uovo tal quale (cairomoni diretti) e/o da stadi diversi da quello di uovo, come per esempio l’adulto (cairomoni indiretti). I sinomoni indotti con l’ovideposizione, capaci di richiamare i parassitoidi delle uova ancor prima che il fitofago possa causare danni, sono un efficace esempio del coinvolgimento “diretto” della pianta nel processo di localizzazione dell’ospite da …

Application of Chemical Cues in Arthropod Pest Management for Orchards and Vineyards

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 behavio…

Rhynchophorus ferrugineus: Behavior, Ecology, and Communication

Red palm weevil (RPW) ecology is characterized by the adults' ability to aggregate on palms. The aggregation process has the functions of protection, feeding, and reproduction for the individuals. Semiochemicals and visual cues strongly influence this behavior at intraspecific and interspecific levels. Adults actively fly over long distances, following chemical cues, such as aggregation pheromone and host plant odor, or visual cues to colonize a new host. The aggregation pheromone of RPW is a male-produced mixture of 4-methyl-5-nonanol (major component) and the related ketone 4-methyl-5-nonanone (minor component). These compounds are largely used in the field to lure males and especially fe…

Chemical ecology meets conservation biological control: identifying plant volatiles as predictors of floral resource suitability for an egg parasitoid of stink bugs

Conservation biological control aims to enhance natural enemy populations in crop habitats, e.g. by providing flowering plants as food resources. Suitable flower species must enhance the survival and fecundity of natural enemies but in addition they also need to be highly attractive and thus frequently visited. To date, few examples exist that have considered both criteria. In this study, we tested the effects of the flowering plants alyssum (Lobularia maritima), buckwheat (Fagopyrum esculentum), French marigold (Tagetes patula) and sweet basil (Ocimum basilicum) on the fecundity and olfactory attractiveness of the egg parasitoid Trissolcus basalis, an important biological control agent of …

Interazioni insetti – piante: i segnali di allarme delle piante e le risposte dei parassitoidi.

Chemical Composition and Evaluation of Insecticidal Activity of Seseli bocconei Essential Oils against Stored Products Pests

In this study, the chemical composition of the essential oils (EOs) obtained from different aerial parts (flowers, leaves, and stems) of Seseli bocconei Guss., a wild species endemic of Sicily, was investigated. Furthermore, the EOs’ biocidal effects towards two pests of stored products, Sitophilus oryzae and Callosobruchus maculates, were evaluated. This activity was evaluated in Petri dish bioassays to establish the survival rate of adults treated with the EOs comparing them with solvent and a commonly used insecticide (pyrethrum). The data obtained from the toxicity bioassay evidenced that stems’ EOs and leaves’ EOs have a contact/fumigation effect towards the two insec…

Paysandisia archon: Taxonomy, distribution, biology and life cycle

The taxonomic position of the family Castniidae within the order Lepidoptera has changed over time. Initially, it was classified in the superfamily Sesioidea, and then it was grouped in a large assemblage including the Cossoidea, Sesioidea, and Zygaenoidea. Recent studies have included it in the superfamily Cossoidea. In Europe, the palm borer moth (PBM) Paysandisia archon is the only species of the Castniidae. This moth, native to South America (Argentina and Uruguay), was first reported in Europe (France and Spain) in 2001, but it is believed to have been introduced before 1995 on palm trees imported from Argentina. Since then, the moth has been reported in Belgium, Bulgaria, Cyprus Islan…

Behavioral response of the egg parasitoid Ooencyrtus telenomicida to host-related chemical cues in a tritrophic perspective

The response of the generalist egg parasitoid Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae) to host-related chemical cues from tomato plants, Solanum lycopersicum L., and adults of Nezara viridula (L.) (Heteroptera: Pentatomidae) was investigated in laboratory-based no-choice and paired-choice tests. In Y-tube olfactometer experiments, when female wasps were exposed to volatiles from plants in different conditions, they were attracted only to volatiles produced by N. viridula adult-infested tomato plants. When female wasps were exposed to adults of N. viridula, they were attracted to volatiles from virgin males, and, at a lower level, to volatiles from mated females in preov…

Role of volatile and contact pheromones in the mating behaviour of Bagrada hilaris (Heteroptera: Pentatomidae)

Volatiles and contact pheromones involved in the mating behaviour of the Painted bug, Bagrada hilaris Burmeister (Het- eroptera: Pentatomidae), were investigated in behavioural and chemical experiments. Vertical open Y-shaped olfactometer bioassays showed that odour from males attract females but not males, while that from females did not attract either gender. Adult females were also attracted by hexane extracts of volatile compounds collected from males. In open arena bioassays, males displayed the characteristic steps of courtship behaviour in the presence of virgin females. Such courtship behaviour was displayed in the presence of females killed by freezing, but not in the presence of f…

Endogenous and exogenous factors affecting the patch time of females of an egg parasitoid.

Verso l’identificazione del feromone sessuale di Contarinia sorghicola (Coquillet)

Bacillus thuringiensis as a biological control agent for the red palm weevil, Rhynchophorous ferrugineus (Oliv.)(Coleoptera, Curculionidae)

Mezzi biotecnici per il controllo degli insetti fitofagi degli agrumi

Individuazione e applicazione di composti volatili repellenti per il controllo delle popolazioni del punteruolo rosso delle palme

The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (Coleoptera, Curculionidae), is one of the most severe pests of ornamental palm species in urban areas of Mediterranean countries. The cryptic nature of the weevil, and the gaps in our knowledge of its biology and ecology, hamper the development of efficient and sustainable strategies to limit its diffusion. Control strategies based on semiochemicals can be considered a suitable alternative for RPW population management, particularly in urban areas. Nevertheless these strategies might be improved by broadening our knowledge of behavior modifying stimuli suitable for adult manipulation, such as repellent chemical compounds. A first…

Contrasting olfactory responses of two egg parasitoids to buckwheat floral scent are reflected in field parasitism rates

International audience; Conservation biological control programs advocate the planting of flower strips alongside crops to improve the survival and effectiveness of parasitoids. Ideally, the provided food plants are highly attractive and benefit the targeted biocontrol agents without promoting pests or intraguild competition. Previous laboratory studies showed that Trissolcus basalis, an egg parasitoid of the stink bug Nezara viridula, is highly attracted to floral odors of buckwheat and that its nectar increases the wasp’s fecundity. In the field, T. basalis competes with the co-occurring parasitoid Ooencyrtus telenomicida for host eggs. Therefore, in the present study, we explored whether…

Behavioral responses of Hyalesthes obsoletus to host-plant volatiles cues

The polyphagous planthopper Hyalesthes obsoletus Signoret is considered to be the principal vector of stolbur phytoplasma, which is associated with yellow diseases of grapevine. To explore the possibility of developing novel control strategies, the behavioral responses to six synthetic mixtures and nine single compounds, previously identified from the headspace of Vitex agnus-castus L. (chaste tree) and Urtica dioica L. (nettle), were investigated in Y-tube bioassays. Choice tests revealed differences in the behavioral responses of males and females to the volatiles that they were exposed to. Males were attracted to a mixture containing (E)-β-caryophyllene, 1,8-cineole, (E,E)-α-farnesene, (…

Testing the habituation assumption underlying models of parasitoid foraging behavior

BackgroundHabituation, a form of non-associative learning, has several well-defined characteristics that apply to a wide range of physiological and behavioral responses in many organisms. In classic patch time allocation models, habituation is considered to be a major mechanistic component of parasitoid behavioral strategies. However, parasitoid behavioral responses to host cues have not previously been tested for the known, specific characteristics of habituation.MethodsIn the laboratory, we tested whether the foraging behavior of the egg parasitoidTrissolcus basalisshows specific characteristics of habituation in response to consecutive encounters with patches of host (Nezara viridula) ch…

Endogenous and exogenous factors affecting host chemical footprint exploitation by a hymenopterous egg parasitoid

During the host location process, parasitoids encounter and explore a great variety of volatile and contact semiochemicals from the host-plant complex. In the system Nezara viridula and its egg parasitoid Trissolcus basalis, when wasps land on a plant, they can taste chemical footprints left by walking adult hosts. These cues represent a set of indirect host-related contact kairomones that induce arrestment and motivated searching behavior, as they drive wasps in an area where there is a high probability of finding hosts but are not able to “promise” the presence of the suitable host stage. Patch time allocation is strongly modified by experience gained during foraging on host traces. In fa…

The role of plant volatiles in prediction of floral resource suitability: chemical ecology to enhance conservation biological control.

Plants emit substantial amounts of volatile organic compounds (VOCs) which represent a decisive communication channel, governing essential decisions insect have to make, such as choice of food. Understanding these interactions is critically important in Habitat Management and in a broader view in Conservation Biological Control. Suitable flower species must enhance the survival and fecundity of natural enemies but in addition they also need to be highly attractive and thus frequently visited. To date few examples exist that have considered both criteria. In this study we tested the effects of the flowering plants alyssum (Lobularia maritima), buckwheat (Fagopyrum esculentum), French marigol…

Controllo naturale dei fitofagi del fico d’India in Sicilia

Use of biorational insecticides for the control of Tuta absoluta (Meyrick) infestations on open field tomato

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 goo…

I semiochimici utilizzati nella localizzazione dell’ospite da parte del parassitoide oofago Ooencyrtus telenomicida

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. viridul…

Competitive interactions in insect parasitoids: effects of microbial symbionts across tritrophic levels

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 micr…

Plant and stink bug interactions at different trophic levels

The interactions between plants and herbivores are among the most important ecological interactions in nature (Johnson 2011). Plants are sessile organisms and cannot run away from potential attackers, which are range from pathogenic microbes to grazing mammals. Among these attackers, arthropods, and in particular insects, comprise the largest and most diverse group of organisms with approximately 1-3 million species feeding on plants (Schoonhoven et al. 2005, Dicke 2009). Host-finding and acceptance or rejection of plants by herbivorous insects depend on their behavioral responses to physical and chemical plant features (Finch and Collier 2000). In this context, the insect-plant interaction…

Evidence of stochastic resonance in the mating behavior of Nezara viridula (L.)

We investigate the role of the noise in the mating behavior between individuals of Nezara viridula (L.), by analyzing the temporal and spectral features of the non-pulsed type female calling song emitted by single individuals. We have measured the threshold level for the signal detection, by performing experiments with the calling signal at different intensities and analyzing the insect response by directionality tests performed on a group of male individuals. By using a sub-threshold signal and an acoustic Gaussian noise source, we have investigated the insect response for different levels of noise, finding behavioral activation for suitable noise intensities. In particular, the percentage…

Trichoderma harzianum Strain T22 Modulates Direct Defense of Tomato Plants in Response to Nezara viridula Feeding Activity

AbstractPlant growth-promoting fungi belonging to genus Trichoderma are known to help plants when dealing with biotic stressors by enhancing plant defenses. While beneficial effects of Trichoderma spp. against plant pathogens have long been documented, fewer studies have investigated their effect on insect pests. Here, we studied the impact of Trichoderma root colonization on the plant defense responses against stink bug feeding attack. For this purpose, a model system consisting of tomato plant, Solanum lycopersicum cv Dwarf San Marzano, Trichoderma harzianum strain T22 and the southern green stink bug, Nezara viridula, was used. We firstly determined stink bug performance in terms of rela…

Integrating natural enemies and semiochemicals in cultural control for an effective IPM

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 se…

Indagini di laboratorio sulla patogenicità di Bacillus thuringiensis nei confronti del Punteruolo rosso delle palme

Host Searching by Egg Parasitoids: Exploitation of Host Chemical Cues

Insect parasitoids are considered “keystone species” in many ecosystems in terms of biodiversity, ecological impact and economic importance (Vinson 1985, LaSalle and Gauld 1993, Hawkins et al. 1999). In the last decades, several reviews have been published on the relationships among plants, hosts and parasitoids, which reflect a strong interest in these insects both as models for behavioral ecologists and as important organisms for classical and applied biological control programs (Hawkins et al. 1999, Vet 1999, Bale et al. 2008). The majority of these studies have considered the larval parasitoid s, besides the extensive use of egg parasitoids in biological control (Hawkins et al. 1999). I…

Action Programs for Rhynchophorus ferrugineus and Paysandisia archon

The spread of invasive alien species is strongly associated with the rapid acceleration of human trade, tourism, transport, and travel over the past century, which have allowed these species to overcome natural geographic barriers. The best strategy to prevent the spread of invasive species is quarantine and eradication of initial foci. However, when invasive species appear to be established, the best approach should focus on containment and decreasing their impact through specific control measures. In this context, considering the rapid spread of the two palm pest species recently introduced in the Mediterranean area-Rhynchophorus ferrugineus (red palm weevil, RPW) and Paysandisia archon (…

Odorants of Capsicum spp. Dried Fruits as Candidate Attractants for Lasioderma serricorne F. (Coleoptera: Anobiidae)

The cigarette beetle, Lasioderma serricorne F. (Coleoptera: Anobiidae) is an important food storage pest affecting the tobacco industry and is increasingly impacting museums and herbaria. Monitoring methods make use of pheromone traps which can be implemented using chili fruit powder. The objective of this study was to assess the response of L. serricorne to the volatile organic compounds (VOCs) from different chili powders in order to identify the main semiochemicals involved in this attraction. Volatiles emitted by Capsicum annuum, C. frutescens, and C. chinense dried fruit powders were tested in an olfactometer and collected and analyzed using SPME and GC-MS. Results indicated that C. an…

Fine Structure of Antennal Sensilla of Paysandisia archon and Electrophysiological Responses to Volatile Compounds Associated with Host Palms

Paysandisia archon (Lepidoptera: Castniidae) is a serious pest of palm trees. A comprehensive knowledge of the insect olfactory system is essential for the development of efficient semiochemical-based control methods. The olfactory sensilla are located particularly on the antennae, and these can detect plant volatiles that provide important cues for the insects in the search for their host plants. To date, the fine structure of P. archon antennal sensilla studies and their role in host-plant perception have not been investigated in great detail. Using light microscopy and scanning and transmission electron microscopy, the antennae of both sexes of P. archon are described here in detail, acc…

Applied Chemical Ecology to Enhance Insect Parasitoid Efficacy in the Biological Control of Crop Pests

The field application of semiochemicals, used by parasitoids to find mates and to locate their hosts, is a promising environmentally sustainable and highly specific pest control strategy and an attractive alternative to the use of pesticides. In this chapter, we first examine research progress dealing with the effect of semiochemical cues on parasitoid foraging strategy. In the second part, we review the possible field applications of these chemical cues to enhance pest control strategies, either through direct pest control or by manipulating parasitoid behaviour. We then consider novel approaches, such as the “attract and reward” strategy, combining semiochemical application and habitat ma…

An invasive insect herbivore disrupts plant volatile-mediated tritrophic signalling

Plants respond to insect attack by emission of volatile organic compounds, which recruit natural enemies of the attacking herbivore, constituting an indirect plant defence strategy. In this context, the egg parasitoid Trissolcus basalis is attracted by oviposition-induced plant volatiles emitted by Vicia faba plants as a consequence of feeding and oviposition by the pentatomid host Nezara viridula. However, this local tritrophic web could be affected by the recent invasion by the alien pentatomid bug Halyomorpha halys, an herbivore that shares the same environments as native pentatomid pests. Therefore, we investigated in laboratory conditions the possible impact of H. halys on the plant vo…

Interazioni tra feromoni dell’ospite e parassitoidi oofagi: meccanismi e implicazioni nel controllo biologico

Members of the WRKY gene family are upregulated in Canary palms attacked by Red Palm Weevil

The Red Palm Weevil (RPW), Rhynchophorus ferrugineus, is one of the major pests affecting several palm species all around the world. The aim of this work was to identify palm genes that are responsive to RPW infestations as a valuable diagnostic tool to detect the insect attack. We have analysed a total of 15 genes that were divided in two subsets: (1) 7 genes previously linked with RPW attacks, but not involved in biotic stress responses, and (2) 8 genes encoding members of the WRKY family, a class of transcription factors well-known to be linked with both abiotic and biotic stress responses. The analysis was conducted on 4-year-old Canary palms comparing uninfested plants and infested pla…

Insect pests of the Herbarium of the Palermo botanical garden and evaluation of semiochemicals for the control of the key pest Lasioderma serricorne F. (Coleoptera: Anobiidae)

Abstract The herbaria are scientific tools of great importance that preserve extinct, rare, endemic, and common plant species and also have importance as Cultural Heritage for their historical and esthetical value. Herbaria can be infested by several insect pests feeding on dried plants, and their management is often complicated and difficult as the use of chemical insecticides can have negative drawbacks. This suggests a strong need for alternative control tools such as the use of semiochemicals to develop Integrated Pest Management (IPM) programs. In order to identify the main insect pests that determine the damages on the exsiccata stored in the Palermo Botanical Garden's Herbarium, one …

Bagrada hilaris (Burmeister) (Heteroptera: Pentatomidae) fitofago dannoso al cappero nell'isola di Pantelleria

Endogenous and exogenous factors affecting the host chemical footprint’s exploitation of an egg parasitoid

During the host location process, parasitoids encounter and explore a great variety of volatile and contact semiochemicals from the host-plant complex. In the system Nezara viridula and its egg parasitoid Trissolcus basalis, when wasps land on a plant, they can taste chemical footprints left by walking adult hosts. These cues represent a set of indirect host-related contact kairomones that induce arrestment and motivated searching behavior, as they drive wasps in an area where there is a high probability of finding hosts but are not able to “promise” the presence of the suitable host stage. Patch time allocation is strongly modified by experience gained during foraging on host traces. In fa…

Paysandisia archon: Behavior, Ecology, and Communication

This chapter on Paysandisia archon behavior, ecology, and communication is presented in three parts. The first part deals with reproductive behavior and the sex pheromone. In this section, mating behavior is described with a consideration of optimal age and diel periodicity. Early observations have shown that mating can occur a few hours after adult molting, from noon to the beginning of the afternoon, according to timing of emergence. The female is described as flying close to perching males and the pair then fly together before mating. The male exhibits a scratching movement with the mid-legs while the female extrudes the abdominal tips. Putative sex pheromone production is discussed in r…

Influenza dell'esperienza del ritrovamento delle tracce ospiti e dell'ovideposizione sul comportamento di localizzazione dell'ospite da parte di Trissolcus basalis

Emergence, dispersal, and mate finding via a substrate-borne sex pheromone in the parasitoidMetaphycus luteolus

Metaphycus luteolus Timberlake (Hymenoptera: Encyrtidae) is a facultatively gregarious parasitoid of soft scale insects. We conducted behavioral experiments to better understand the mating structure of this species. Emergence of male and female offspring is synchronized, beginning at the onset of photoperiod. Both sexes are able to disperse, although dispersal of males from natal patches appears to take longer than dispersal of females. We demonstrated the presence of a female-produced contact pheromone using open arena bioassays and motion tracking software, testing residues deposited by walking females, and extracts of females. Males responded to the females' chemical footprints' and to a…

A female-produced short-range sex pheromone in the egg parasitoid Trissolcus brochymenae

The potential for short-range sex pheromone communication by the egg parasitoid wasp Trissolcus brochymenae (Hymenoptera: Platygastridae) was investigated in closed arena bioassays. Males of this parasitoid showed more antennal drumming and more frequent mounting behaviour on 1- to 2-d-old virgin females compared with 8-d-old virgin females. Male copulation attempts were fewer with previously mated females than with virgin females. Males courted and made copulation attempts with 1- to 2-d-old female cadavers, but not with male cadavers or with female cadavers rinsed in organic solvents of different polarities. Male attraction to female cadavers was re-established by treating cadavers with a…

Assessment of synthetic chemicals for disruption of Rhynchophorus ferrugineus attraction in an urban environment

The red palm weevil (RPW), Rhynchophorus ferrugineus Olivier (Coleoptera, Curculionidae), is currently one of the most severe pests of Canary palms in urban areas of Mediterranean countries and date palms in cultivated areas of the Middle East. RPW aggregation pheromone can be implemented for both monitoring and mass trapping however risks of RPW 'spillover' onto palms is of great concern. Aim of this work was to discover repellent semiochemicals for RPW population management in urban environments. For this purpose we conducted electroantennographic (EAG) screenings of 17 commercially available synthetic compounds, representing three groups of plant volatiles (isoprenoids, phenyl propanoid …

Role of host cues and oviposition-induced plant signals on the host location behaviour of the egg parasitoid Trissolcus basalis

Noise effects in two different biological systems

We investigate the role of the colored noise in two biological systems: (i) adults of Nezara viridula (L.) (Heteroptera: Pentatomidae), and (ii) polymer translocation. In the first system we analyze, by directionality tests, the response of N. viridula individuals to subthreshold signals plus noise in their mating behaviour. The percentage of insects that react to the subthreshold signal shows a nonmonotonic behaviour, characterized by the presence of a maximum, as a function of the noise intensity. This is the signature of the non-dynamical stochastic resonance phenomenon. By using a “soft” threshold model we find that the maximum of the input-output cross correlation occurs in the same ra…

The response of an egg parasitoid to substrate-borne semiochemicals is affected by previous experience

AbstractAnimals can adjust their behaviour according to previous experience gained during foraging. In parasitoids, experience plays a key role in host location, a hierarchical process in which air-borne and substrate-borne semiochemicals are used to find hosts. In nature, chemical traces deposited by herbivore hosts when walking on the plant are adsorbed by leaf surfaces and perceived as substrate-borne semiochemicals by parasitoids. Chemical traces left on cabbage leaves by adults of the harlequin bug (Murgantia histrionica) induce an innate arrestment response in the egg parasitoid Trissolcus brochymenae characterized by an intense searching behaviour on host-contaminated areas. Here we …

Investigation of cuticular hydrocarbons from Bagrada hilaris genders by SPME/GC-MS

The cuticular hydrocarbons of male and female Bagrada hilaris Burmeister (Heteroptera: Pentatomidae) were investigated, by headspace solid-phase microextraction followed by gas chromatography-mass spectrometry. Measurements were done with fiber coatings of different polarity after optimization of headspace volumes and extraction temperatures. This resulted in the use of polyacrylate fiber, 22-ml vial as the sample holder, and an extraction temperature of 150 degrees C. The analytical procedures allowed identification of 13 peaks, corresponding to a homologous series of n-alkanes (nC(17)-nC(29)). The hydrocarbon profiles of male and female B. hilaris were qualitatively equal, but marked sex-…

Interspecific competition/facilitation among insect parasitoids.

Competition for limited resources is a widespread ecological interaction in animals. In the case of insect parasitoids, species can compete for host resources both at the adult stage as well as at the larval stage. Interspecific competition can play a role in sizing and shaping community structures. In addition of being relevant for basic ecological studies, understanding how interspecific competition between parasitoids affects pest suppression is important for biological control. In this opinion paper we review recent advances in the field of interspecific competition among parasitoids in a biological control perspective. We first discuss adult competition, highlighting which factors are …

Impact of the invasive painted bug, Bagrada hilaris on physiological traits of its host Brassica oleracea var botrytis

Bagrada hilaris is a herbivorous insect native of Asia and Africa, which has invaded southern Europe and North America where it causes major damage to cole crops. Laboratory experiments were conducted to assess how the infestation of this invasive species damages the host Brassica oleracea var botrytis, and to evaluate the interaction between plant emission of volatile organic compounds (VOC) and B. hilaris adults. Plant responses to insect feeding were evaluated through changes in photosynthesis, stomatal conductance, VOC emission, and visual damage on leaves. The impact of B. hilaris was compared with that of Nezara viridula, a polyphagous species distributed worldwide. Plant VOC role in …

La Tecnica della microestrazione in fase solida (SPME) per l'analisi quantitativa e qualitativa dei feromoni sessuali degli insetti fitofagi: il caso della Cocciniglia bianca del limone

Responses of Rhynchophorus ferrugineus adults to selected synthetic palm esters: electroantennographic studies and trap catches in an urban environment

The Red Palm Weevil (RPW), Rhynchophorus ferrugineus Olivier, accidentally introduced in the European countries facing the Mediterranean basin, is becoming the most serious pest for ornamental palms in the urban environment. In our work we tested electroantennogram (EAG) and behavioural responses of RPW adults to five selected synthetic palm esters: ethyl propionate, ethyl butyrate, ethyl isobutyrate, ethyl lactate and ethyl acetate. EAG bioassays showed higher sensitivity of female antennae compared to male antennae for test compounds. Differences were also recorded in the EAG responses using different esters and doses. Ethyl propionate was the synthetic ester that elicited the strongest r…

Impiego dei nematodi entomopatogeni in ambiente urbano per il controllo del Punteruolo rosso

Ottimizzazione del comportamento di ricerca di un parassitoide oofago in presenza di stimoli indirettamente associati all'ospite.

Relazioni intra-associative in ambiente forestale: il caso dei parassitoidi oofagi della Processionaria del Pino

The Egg Parasitoid Trissolcus basalis uses n-nonadecane, a Cuticular Hydrocarbon from its Stink Bug Host Nezara viridula, to Discriminate Between Female and Male Hosts

Contact kairomones from adult southern green stink bugs, Nezara viridula (L.) (Heteroptera: Pentatomidae) that elicit foraging behavior of the egg parasitoid Trissolcus basalis (Wollaston) were investigated in laboratory experiments. Chemical residues from tarsi and scutella of N. viridula induced foraging by gravid female T. basalis. Residues from body parts of female N. viridula elicited stronger responses than those from the corresponding body parts of males. Deproteinized tarsi still elicited searching responses from wasps, indicating that the kairomone was not proteinaceous. Hexane extracts of host cuticular lipids induced searching responses from T. basalis, with a strong preference f…

The response of Trissolcus basalis to footprint contact kairomones from Nezara viridula females is mediated by leaf epicuticular waxes.

Chemical footprints left behind by true bugs are perceived as contact kairomones by scelionid egg parasitoids. Female wasps encountering a contaminated artificial substrate display a characteristic arrestment posture, holding the body motionless and antennating the surface. In the system Nezara viridula (L.) and its egg parasitoid Trissolcus basalis (Wollaston), previous studies have shown that the kairomone mediating such behavior is part of N. viridula's cuticular hydrocarbons (CHC) and furthermore that the wasp's ability to discriminate host male and female footprints is mainly based on the presence/absence of nonadecane (nC(19)). In this study, the effect of epicuticular waxes of leaves…

Electrophysiological responses of Contarinia sorghicola (Coquillett) (Diptera, Cecidomyiidae) to candidate sex pheromone compounds.

Contrasting reproductive traits of competing parasitoids facilitate coexistence on a shared host pest in a biological control perspective

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 …

Intraguild interactions between egg parasitoids: window of opportunity and fitness costs for a facultative hyperparasitoid.

We investigated intraguild interactions between two egg parasitoids of Nezara viridula (L.) (Heteroptera: Pentatomidae), Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae) and Trissolcus basalis (Wollaston) (Hymenoptera: Platygastridae), as the former has the potential to be a facultative hyperparasitoid of the latter. We assessed the suitability of N. viridula eggs for the development of O. telenomicida as a function of egg age when they were unparasitized, or had been attacked by T. basalis at different times prior to exposure to O. telenomicida females. Ooencyrtus telenomicida can exploit healthy N. viridula host eggs up to 5 days of age, just prior to the emergence of N. viri…

Impiego dei feromoni in agrumicoltura per il contenimento degli insetti fitofagi: stato attuale e prospettive