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Turlings, Ted

Nom
Turlings, Ted
Affiliation principale
Fonction
Professeur.e ordinaire
Email
ted.turlings@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/330
_
0000-0002-8315-785X

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  • Publication
    Accès libre
    A comparison of naïve and conditioned responses of three generalist endoparasitoids of lepidopteran larvae to host-induced plant odours
    (2006)
    Tamò, Cristina
    ;
    Ricard, Ingrid
    ;
    Held, Matthias 
    ;
    Davison, A. C.
    ;
    Turlings, Ted 
    Many parasitic wasps that exploit herbivores as their hosts make use of herbivoreinduced plant odours to locate their victims and these wasps often exhibit an ability to learn to associate specific plant-produced odours with the presence of hosts. This associative learning is expected to allow generalist parasitoids to focus on cues that are most reliably associated with current host presence, but evidence supporting this hypothesis is ambiguous. Using a six-arm olfactometer we compared the responses of three generalist larval endoparasitoids, Cotesia marginiventris (Hymenoptera: Braconidae), Microplitis rufiventris (Hymenoptera: Braconidae) and Campoletis sonorensis (Hymenoptera: Ichneumonidae), to the induced odours of three plant species: maize (Zea mays), cowpea (Vigna unguiculata), and cotton (Gossypium hirsutum). We tested the responses of naïve females as well as of females that were first conditioned by parasitising host larvae feeding on one of the plant species. Despite similarities in biology and host range the three wasp species responded entirely differently. Naïve C. marginiventris and C. sonorensis chose equally among the induced odours of the three plants, whereas naïve M. rufiventris, which may have a somewhat more restricted host range, tended to prefer the odour of maize. After conditioning, most C. marginiventris females chose the odour of the plant species that they had experienced, but conditioned M. rufiventris showed an even stronger preference for maize odours, independently of the plant they had experienced. Cotesia sonorensis did not show any change in its preference after conditioning. We speculate that its extremely broad host range allows C. sonorensis females to use fixed responses to cues commonly associated with plants damaged by Lepidoptera. These results imply that different generalist parasitoids may employ different foraging strategies and that associative learning is not necessarily part of it.
  • Publication
    Accès libre
    Odour-mediated long-range avoidance of interspecific competition by a solitary endoparasitoid : a time-saving foraging strategy
    (2006)
    Tamò, Cristina
    ;
    Roelfstra, Lise-Lore
    ;
    Guillaume, Suzanne
    ;
    Turlings, Ted 
    1. In studies on optimal foraging strategies, long-range decisions in the pursuit of resource are rarely considered. This is also the case for sympatric parasitoids, which may be confronted with the decision to accept or reject host larvae that are already parasitized by a competing species. They can be expected to reject already parasitized hosts if it is likely that they will lose the resulting intrinsic competition. However, examples of such interspecific host discrimination are rare.
    2. We propose that parasitoids that are not egg-limited should reject inferior hosts only if it saves them time, and that this will be achieved mainly when the parasitoids are able to detect competitors from a distance. We tested this hypothesis using the sympatric parasitoids Cotesia marginiventris (Cresson) and Campoletis sonorensis (Cameron).
    3.C. sonorensis was found to be the superior intrinsic competitor but, upon contact with a host larva, both wasps readily accepted hosts that had already been parasitized by the other species. However, in an olfactometer experiment, C. marginiventris females were found to strongly avoid the odour of their superior competitor.
    4. These results are in accordance with a time optimization scenario, whereby the inferior competitor accepts competition if it costs only an egg, but avoids competition if it may save time that can be allocated to the search for more profitable hosts.
    5. Models on host discrimination strategies in parasitoids had not yet considered discrimination from a distance. Long-range foraging decisions can also be expected for other organisms that have to choose between resources of varying suitability and profitability.
  • 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.