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Degen, Thomas

Nom
Degen, Thomas
Affiliation principale
Email
thomas.degen@unine.ch
Identifiants
https://libra.unine.ch/handle/123456789/354
_
0000-0003-2101-2433

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  • Publication
    Accès libre
    Odor-based real-time detection and identification of pests and diseases attacking crop plants
    (2024-07-29)
    Marques Arce, Carla C. 
    ;
    Mamin, Marine 
    ;
    Terunobu Akiyama
    ;
    Röder, Gregory 
    ;
    Kanagendran, Arooran 
    ;
    Kosuke Minami
    ;
    Degen, Thomas 
    ;
    Genki Yoshikawa
    ;
    Defossez, Emmanuel 
    ;
    Felipe Lopez-Hilfiker
    ;
    Rasmann, Sergio 
    ;
    Luca Cappellin
    ;
    Turlings, Ted 
    Plants respond to attacks by herbivores and pathogens by releasing specific blends of volatile compounds and the resulting odor can be specific for the attacking species. We tested if these odors can be used to monitor the presence of pests and diseases in agriculture. Two methods were used, one employing piezoresistive membrane surface stress sensors and the other proton-transfer reaction mass spectrometry. Under laboratory conditions, both techniques readily distinguished between maize plants that were either undamaged, infested by caterpillars, or infected by a fungal pathogen. Under outdoor conditions, the spectrometer could be used to recognize plants with simulated caterpillar damage with about 80% accuracy. Further finetuning of these techniques should lead to the development of odor-sensing mobile devices capable of alerting farmers to the presence and exact location of pests and diseases in their fields.
  • Publication
    Accès libre
    The combined use of an attractive and repellent sex pheromonal component by a gregarious parasitoid
    (2019-3-28)
    Xu, Hao 
    ;
    Dötterl, Stefan
    ;
    Zhou, Guoxin 
    ;
    Schäffler, Irmgard
    ;
    von Arx, Martin
    ;
    Röder, Gregory 
    ;
    Degen, Thomas 
    ;
    Chen, Li 
    ;
    Turlings, Ted 
    Gregarious parasitoids usually clump their cocoons together and the adults emerge in a synchronized fashion. This makes it easy for them to find mating partners and most copulations indeed take place at the natal patch. Yet, males should leave such sites when females are no longer receptive. As yet, this decision-making process and the possible involvement of pheromones were poorly understood. Here we report on a remarkable use of attractive and repellent pheromones of the well-studied gregarious parasitoid species Cotesia glomerata (L.) (Hymenoptera: Braconidae). Virgin C. glomerata females were found to release an attractive as well as a repellent compound, which in combination arrest males on the natal patch, but after mating the females stop the production of the attractant and the males are repelled. The repellent compound was identified as heptanal, which was also released by males, probably reducing male-male competition on the natal patch. We also confirmed that the sex ratio of the emerging wasps can vary considerably among patches, depending on the relative quality of hosts and the number of females that parasitize a host. The newly revealed use of attractive and repellent pheromone compounds by C. glomerata possibly helps maximize mating success under these variable conditions.