Volatile organic compounds (VOCs) emitted by fungi play a key role in locating and selecting hosts for fungivorous arthropods. However, the ecological functions of many common VOC classes, such as sesquiterpenes, remain unknown. Mutants of
Trichoderma virens
, defective in the emission of most sesquiterpenes owing to the deletion of the terpene cyclase
vir4
, were used to evaluate the role of this compound class in the food preference and fitness of the soil Collembola
Folsomia candida.
Choice experiments with and without direct contact with fungal mycelium revealed that Collembola were preferentially attracted to
Δvir4
mutants impaired in sesquiterpene synthesis compared to wild-type
T. virens
. Grazing by
F. candida
on the sesquiterpene deficient
T. virens
strain had no effect on Collembola survival, reproduction and growth compared to wild-type
T. virens
. The results suggest that sesquiterpenes play an important role in fungal defence as repellents, but not as deterrents or toxins, against fungivorous Collembola. Our research contributes to the understanding of ecological interactions between fungi and fungivorous arthropods, providing insights into the specific ecological functions of sesquiterpenes. The study has implications for chemical ecology and the dynamics of multitrophic interactions in soil ecosystems.