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Turlings, Ted

Nom
Turlings, Ted
Affiliation principale
Fonction
Professeur ordinaire
Email
ted.turlings@unine.ch
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https://libra.unine.ch/handle/123456789/330

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  • Publication
    Métadonnées seulement
    Strong attraction of the parasitoid Cotesia marginiventris towards minor volatile compounds of maize
    (2009-9)
    D'Alessandro, Marco
    ;
    Brunner, V.
    ;
    von Mérey, Georg E.
    ;
    Turlings, Ted 
    Plants infested with herbivorous arthropods emit complex blends of volatile compounds, which are used by several natural enemies as foraging cues. Despite detailed knowledge on the composition and amount of the emitted volatiles in many plant-herbivore systems, it remains largely unknown which compounds are essential for the attraction of natural enemies. In this study, we used a combination of different fractionation methods and olfactometer bioassays in order to examine the attractiveness of different compositions of volatile blends to females of the parasitoid Cotesia marginiventris. In a first step, we passed a volatile blend emitted by Spodoptera littoralis infested maize seedlings over a silica-containing filter tube and subsequently desorbed the volatiles that were retained by the silica filter (silica extract). The volatiles that broke through the silica filter were collected on and subsequently desorbed from a SuperQ filter (breakthrough). The silica extract was highly attractive to the wasps, whereas the breakthrough volatiles were not attractive. The silica extract was even more attractive than the extract that contained all herbivore-induced maize volatiles. Subsequently, we fractioned the silica extract by preparative gas-chromatography (GC) and by separating more polar from less polar compounds. In general, C. marginiventris preferred polar over non-polar compounds, but several fractions were attractive to the wasp, including one that contained compounds emitted in quantities below the detection threshold of the GC analysis. These results imply that the attractiveness of the volatile blend emitted by Spodoptera-infested maize seedlings to C. marginiventris females is determined by a specific combination of attractive and repellent/masking compounds, including some that are emitted in very small amounts. Manipulating the emission of such minor compounds has the potential to greatly improve the attraction of certain parasitoids and enhance biological control of specific insect pests.
  • Publication
    Accès libre
    Strong Attraction of the Parasitoid Cotesia marginiventris Towards Minor Volatile Compounds of Maize
    (2009)
    D’Alessandro, Marco
    ;
    Brunner, Virginie
    ;
    von Mérey, Georg
    ;
    Turlings, Ted 
    Plants infested with herbivorous arthropods emit complex blends of volatile compounds, which are used by several natural enemies as foraging cues. Despite detailed knowledge on the composition and amount of the emitted volatiles in many plant-herbivore systems, it remains largely unknown which compounds are essential for the attraction of natural enemies. In this study, we used a combination of different fractionation methods and olfactometer bioassays in order to examine the attractiveness of different compositions of volatile blends to females of the parasitoid Cotesia marginiventris. In a first step, we passed a volatile blend emitted by Spodoptera littoralis infested maize seedlings over a silica-containing filter tube and subsequently desorbed the volatiles that were retained by the silica filter (silica extract). The volatiles that broke through the silica filter were collected on and subsequently desorbed from a SuperQ filter (breakthrough). The silica extract was highly attractive to the wasps, whereas the breakthrough volatiles were not attractive. The silica extract was even more attractive than the extract that contained all herbivore-induced maize volatiles. Subsequently, we fractioned the silica extract by preparative gas-chromatography (GC) and by separating more polar from less polar compounds. In general, C. marginiventris preferred polar over non-polar compounds, but several fractions were attractive to the wasp, including one that contained compounds emitted in quantities below the detection threshold of the GC analysis. These results imply that the attractiveness of the volatile blend emitted by Spodoptera-infested maize seedlings to C. marginiventris females is determined by a specific combination of attractive and repellent/masking compounds, including some that are emitted in very small amounts. Manipulating the emission of such minor compounds has the potential to greatly improve the attraction of certain parasitoids and enhance biological control of specific insect pests.
  • Publication
    Accès libre
    The nutritional value of aphid honeydew for non-aphid parasitoids
    (2008)
    Faria, Cristina A.
    ;
    Wäckers, Felix L.
    ;
    Turlings, Ted 
    Die Aufnahme von zuckerreicher Nahrung durch adulte Parasitoide ist entscheidend für ihren reproduktiven Erfolg. Daher sollte die Verfügbarkeit von geeigneter Nahrung die Effizienz von Parasitoiden als Mittel der biologischen Kontrolle steigern. Wenn Nektar nicht leicht verfügbar ist, kann der Honigtau von Homopteren eine entscheidende alternative Nahrungsquelle sein. Wir untersuchten den Einfluss des Honigtaukonsums auf die Lebensdauer der larvalen Endoparasitoide Cotesia marginiventris, Campoletis sonorensis und Microplitis rufiventris, die natürliche Feinde wichtiger Schadlepidopteren sind. Verglichen mit Kontroll-Weibchen, die nur Wasser erhielten, lebten die Weibchen dieser Wespen länger, wenn sie von der Blattlaus Rhopalosiphum maidis (auf Gerste) produzierten Honigtau aufgenommen hatten. Allerdings lebten sie kürzer als Weibchen, die mit einer Saccharose-Lösung gefüttert wurden. Untersuchungen an C. marginiventris zeigten, dass Zugang zu Honigtau auch die Nachkommenzahl erhöhte, wenn auch in geringerem Maße als Saccharose-Lösung. Für optimale Lebensdauer und Reproduktion mussten die Weibchen mehrmals während ihres Lebens trinken. Die Zucker-Zusammensetzung des Honigtaus variierte mit der Größe der Blattlauskolonie und der Dauer ihres Bestehens. Im Allgemeinen sank der von den Blattläusen synthetisierte Zuckeranteil im Honigtau mit der Stärke des Blattlausbefalls. Versuche mit gemischten Zucker-Lösungen (nachgeahmtem Honigtau) erlaubten uns die Hypothese zurückzuweisen, dass der relativ schlechte Lebenserfolg des Parasitoiden bei Honigtau-Diät auf die Zucker-Zusammensetzung zurückzuführen sei. Vielmehr zeigten zusätzliche Versuche mit verdünntem Honigtau, dass der Nährwert von reinem Honigtau primär durch seine hohe Viskosität eingeschränkt wird. Die möglichen Konsequenzen dieser Befunde für die Biologische Schädlingsbekämpfung werden diskutiert., Intake of sugar-rich foods by adult parasitoids is crucial for their reproductive success. Hence, the availability of suitable foods should enhance the efficacy of parasitoids as biological control agents. In situations where nectar is not readily available, homopteran honeydew can be a key alternative food source. We studied the impact of honeydew feeding on the longevity of the larval endoparasitoids Cotesia marginiventris, Campoletis sonorensis and Microplitis rufiventris, all natural enemies of important lepidopteran pests. Females of these wasps lived longer when feeding on honeydew produced by the aphid Rhopalosiphum maidis on barley compared to control females provided with water only. However, they lived shorter than females fed with a sucrose solution. Further investigations with C. marginiventris showed that access to honeydew also increases the number of offspring produced, but less so than access to a sucrose solution. Moreover, it was found that females of this species need to feed several times throughout their life in order to reach optimal longevity and reproductive output. Analyses of the sugars in the honeydew produced by R. maidis on barley revealed that it contains mainly plant-derived sugars, but also several aphid-synthesized sugars. The sugar composition of the honeydew changed as a function of aphid colony size and time a colony had been feeding on a plant. In general, the higher the aphid infestation, the smaller the percentage of aphid-synthesized sugars in the honeydew. Experiments with honeydew sugar mimics allowed us to reject the hypothesis that the relatively poor performance of the parasitoid on a honeydew diet was due to the sugar composition. Instead, the results from additional feeding experiments with diluted honeydew showed that the nutritional value of pure honeydew is primarily restricted by its high viscosity. The possible consequences of these findings for biological pest control are discussed.
  • Publication
    Accès libre
    Occurrence and direct control potential of parasitoids and predators of the fall armyworm (Lepidoptera: Noctuidae) on maize in the subtropical lowlands of Mexico
    (2004)
    Hoballah, Maria Elena
    ;
    Degen, Thomas 
    ;
    Bergvinson, David
    ;
    Savidan, Anita
    ;
    Tamò, Cristina
    ;
    Turlings, Ted 
    1 Native natural enemies have the potential to control fall armyworm Spodoptera frugiperda (Smith) in tropical maize grown in Mexico, where this insect pest causes severe economic losses to farmers. It has been proposed that enhancing herbivore-induced volatile emissions in maize plants may help to increase the effectiveness of natural enemies, which use these volatiles to locate their prey. This will only be of immediate benefit to farmers if the activity of the natural enemies results in a direct reduction in herbivory. Here we report on field surveys for the most common natural enemies in a tropical maize-growing region in Mexico and the potential effects of these enemies on herbivory by fall armyworm.
    2 Caterpillars were collected in maize fields near Poza Rica in the state of Veracruz during January and February 1999, 2000 and 2001. Plants were either naturally infested by S. frugiperda, or artificially infested with laboratory-reared larvae. Ten species of parasitoids emerged from the collected larvae and eight species of predators that are known to feed on larvae and eggs were observed on the plants. Campoletis sonorensis (Cameron) (Hymenoptera: Ichneumonidae) was the dominant parasitoid species, in 1999 and 2001.
    3 Of the nine larval parasitoids collected, six (all solitary) are known to reduce herbivory, whereas one causes the host to eat more (for two species this is not known). This implies that enhancing the effectiveness of solitary endoparasitoids may benefit subsistence farmers in developing countries by immediately reducing herbivory. The overall benefit for the plant resulting from parasitoid activity also has important implications for the evolutionary role of parasitoids in contributing to selection pressures that shape indirect defences in plants.