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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
    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
    Parasotoid communities and genetic structure: host plant does not matter
    (2008)
    Jourdie, Violaine
    ;
    Turlings, Ted 
    Plant-insect interactions have long been studied and reveal intricate mechanisms. Plants are capable of defending themselves both directly by poisoning insect herbivores and indirectly by emitting volatile compounds that are used by the natural enemies to localize their host. In response, insects have evolved strategies to defeat plant defense mechanisms. Because insect pests are affected by plant signals, their natural enemies also bear these effects. As host plant can affect the physiology and behavior of parasitoids, it may also contribute to shaping their population genetic structure. This thesis mainly aimed to investigate the effects of host plant on the population genetics of parasitoids of the fall armyworm (FAW), Spodoptera frugiperda J. E. Smith (Lepidoptera: Noctuidae), using microsatellite markers. The FAW is one of the New World’s most devastating pests and it attacks several economically important crops as well as grasses. It is commonly controlled by chemical insecticides. However, as it is attacked by numerous parasitoids species, and in order to limit the use of toxic pesticides, biological control is a safer alternative mean of management for this pest. The success of biological control relies on a good knowledge of the system, hence the importance of investigating population genetics and communities structure. This study focused on two primary parasitoids of S. frugiperda, Chelonus insularis Cresson (Hymenotera: Braconidae) and Campoletis sonorensis Cameron (Hymenoptera: Ichneumonidae). It was conducted on two host plants, maize and sorghum, in Mexico where maize originated and where sorghum was introduced barely over a century ago. Due to difficulties encountered during sampling, whereby immature parasitoids did not complete their life cycle and therefore could not be morphologically identified, a technique was first developed, as a cheaper and faster alternative to sequencing, to molecularly assign parasitoid larvae to species. This simple but nonetheless efficient technique consists in amplifying DNA through polymerase chain reaction and digesting it with a cocktail of restriction endonucleases in order to obtain a species specific pattern when the digestion product is run on an agarose gel. With this technique, we could get an accurate estimation of which species were collected and in what proportions, which allowed to study parasitoid community structure. The study of population genetics first required the development and optimization of reliable molecular markers. Fifteen and 13 highly polymorphic microsatellites were respectively isolated from C. sonorensis and from C. insularis. These markers were used to investigate fine-scale genetic structure in Mexican populations. We could discern a regional effect, but host plant seems to play no role in shaping the populations genetic structure. High levels of admixture indicate that gene flow between populations is considerable. Finally, genetic structure was investigated at larger scale through a phylogeography using sequences of mitochondrial and nuclear marker genes. The lack of local structure was confirmed for both species. We found however evidence for North-South migration through a single colonization event in C. insularis, and a cryptic species distributed in Canada was discovered. Dispersal of these insects seems to be largely driven by wind as suggested by genetic similarities between geographically very distant individuals.
  • Publication
    Accès libre
    Role of plant volatiles in host location by the specialist parasitoid Microplitis croceipes cresson (Braconidae: Hymenoptera)
    (1993)
    McCall, Philip J.
    ;
    Turlings, Ted 
    ;
    Lewis, W. Joe
    ;
    Tumlinson, James H.
    A study was conducted to determine the primary source of volatile cues within the plant-host complex used by hostseeking freeflying female Microplitis cro-ceipesCresson in flight tunnel bioassays. In single-source and two-choice tests, using wasps given an oviposition experience on either cotton (Gossypium hirsutum) or cowpea (Vigna unguiculata) seedlings damaged by corn earworm (CEW; Helicoverpa zea Boddie), the damaged seedlings were significantly more attractive than the CEW frass, which was in turn more attractive than the larvae themselves. In a series of two-choice wind-tunnel tests, the discriminatory ability of the wasps was examined, following various oviposition experiences. Significantly more wasps flew to plants with old damage than to plants with fresh damage, regardless of whether they had experience on fresh or old damage. In a comparison of plant species, wasps with only one experience on either hostdamaged cotton or host-damaged cowpea were unable to distinguish between them, and showed no preference for either plant, whereas wasps with multiple experiences on a particular plant preferentially flew to that plant in the choice test. In comparing hosts with nonhosts, wasps successfully learned to distinguish CEW from beet armyworm (BAW; Spodoptera exigua) on cotton but were unable to distinguish CEW from either BAW or cabbage looper (Trichoplusia ni) on cowpea. The results show the important role played by plant volatiles in the location of hosts by M. croceipesand indicate the wasps limitations in discriminating among the various odors. The ecological advantages and disadvantages of this behavior are discussed.
  • Publication
    Accès libre
    Isolation and identification of allelochemicals that attract the larval parasitoid, Cotesia marginiventris (Cresson), to the microhabitat of one of its hosts
    (1991)
    Turlings, Ted 
    ;
    Tumlinson, James H.
    ;
    Heath, Robert R.
    ;
    Proveaux, Adron T.
    ;
    Doolittle, Robert E.
    Volatiles released from corn seedlings on which beet armyworm larvae were feeding were attractive to females of the parasitoid, Cotesia marginiventris (Cresson), in flight tunnel bioassays. Analyses of the collected volatiles revealed the consistent presence of 11 compounds in significant amounts. They were: (Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexen-1-ol, (Z)- 3-hexen-1-yl acetate, linalool, (3E)-4,8-dimethyl-1,3,7-nonatriene, indole, α-trans-bergamotene, (E)-β-farnesene, (E)-nerolidol, and (3E,7E)-4,8,12-trimethyl-1, 3,7,ll-tridecatetraene. A synthetic blend of all 11 compounds was slightly less attractive to parasitoid females than an equivalent natural blend. However, preflight experience with the synthetic blend instead of experience with a regular plant-host complex significantly improved the response to the synthetic blend. Our results suggest that C. marginiventris females, in their search for hosts, use a blend of airborne semiochemicals emitted by plants on which their hosts feed. The response to a particular odor blend dramatically increases after a parasitoid experiences it in association with contacting host by-products.