Manipulation of below-ground scents for the benefit of agriculture

Insect herbivory induces the synthesis and release of specific volatile compounds in plants. These volatiles have been shown to be highly attractive to natural enemies of the herbivores, such as predators, parasitic wasps or entomopathogenic nematodes. Few key compounds mediating these so-called tritrophic interactions are known, but in most cases they remain to be identified. In maize, the volatiles emitted upon feeding by leaf- or root feeding arthropod herbivores have been particularly well studied in the laboratory. Moreover, several genes and biochemical pathways responsible for the production of the emitted volatiles have been elucidated and described. These advances in understanding the volatile emissions and their ecological significance open up novel ways to modify plant volatile blends in order to enhance their attractiveness to natural enemies. Here we briefly describe some of the approaches that can be applied to exploit herbivore-induced volatile blends to enhance biological control of belowground herbivores of maize. Based on the available literature, we conclude that the most promising results can be obtained by manipulating the emission of specific volatile compounds, while simultaneously enhancing the responsiveness of natural enemies to particular compounds. However, such manipulative strategies require great caution and we emphasize the importance of taking a holistic ecological approach and to precisely evaluate risks and benefits of modifying volatile blends in the context of pest management.