A repellent plant to regulate aerial pests: Testing the continuum trait-function-service from the lab to polytunnels

Abstract: Enhancing plant functional diversity is a key agroecological strategy to deliver
ecosystem services, notably sustainable pest regulation. In these studies, we assessed the
biocontrol potential of Tagetes spp. across multiple experimental scales following a trait –
function – service framework. Laboratory assays showed that three Tagetes species
significantly reduced whitefly settlement and oviposition on tomato through both physical and olfactory deterrence mechanisms. Greenhouse trials confirmed that intercropping tomatoes with T. minuta suppressed whitefly populations over time. At the field scale (tunnel conditions), T. erecta reduced aphid abundance in pepper crops without adversely affecting natural enemies. However, a slight reduction in crop yield suggested the occurrence of competition between the crop and the companion plant. Overall, marigolds (Tagetes spp.) emerge as multi‑target biocontrol plants (also demonstrating efficacy against phytoparasitic nematodes in parallel assays) but require careful implementation to mitigate potential agronomic disservices.