Research interests We mainly study the chemical ecology of plant-insect interactions. By unraveling how plants defend themselves against insect attacks and how specialized insects have evolved to circumvent these defenses, we hope to provide ideas for novel, sustainable strategies for the control of agricultural pests. Quite some years ago, we revealed that plants under attack by caterpillars initiate a systemic release of specific volatiles. This plant response results in an odour that serves as a signal used by parasitic wasps to locate their hosts, whereas several herbivorous insects are repelled by the odour. Studies into the mechanisms of the plant response showed that it is greatly enhanced by factors in the oral secretions of herbivorous insects. This work initially started at the USDA in Gainesville, Florida, where we eventually isolated and identified a powerful elicitor from the regurgitant of Spodoptera larvae, a fatty acid-amino acid conjugate, which was named volicitin. We also studied how caterpillar-induced volatiles can prime neighboring plants to prepare for incoming attack, and we identified indole as a key inducible volatile in such interactions among maize plants. Our work at the University of Neuchâtel on root signals revealed that root feeding by larvae of the important maize pest Diabrotica virgifera virgifera results in the release of E-(β)-caryophyllene. This sesquiterpene was identified with the help of our collaborators at the Max Planck Institute for Chemical Ecology in Jena and was found to be highly attractive to entomopatogenic nematodes. Many American maize lines do not release this signal and this is reflected in poor attraction of and infection by the nematodes in field experiments conducted with the help of scientists at CABI Bioscience, Switzerland. By genetically transforming a non-emitting maize line we obtained ultimate evidence for the key role of E-(β)-caryophyllene in the attraction of entomopathogenic nematodes. Now that we have obtained considerable insight into the ecology and the mechanisms of these above- and belowground multi-trophic level interactions, we are applying this knowledge to better understand the evolutionary, ecological and applicable aspects of chemical signalling between plants and insects. It is envisioned that our studies will contribute to the development of sustainable pest management practices inspired by nature.