Comparison of morphological and biochemical traits of four companion plants interplanted in an apple orchard and their consequences on the natural enemies involved in the control of rosy apple aphid

Abstract: Sustainable aphid management is a major challenge in fruit production as pesticide
use and efficacy continue to decline. Introducing companion plants (CPs) into orchards is a
promising but understudied strategy, especially in apple systems. Some CPs emit volatile
organic compounds (VOCs) that may repel aphids or attract natural enemies (NEs), yet their
effectiveness under orchard conditions remains poorly documented. We investigated how four CP species (Ocimum basilicum, Tagetes patula, Mentha × piperita and Foeniculum vulgare) interplanted in the tree row influence the regulation of the rosy apple aphid Dysaphis plantaginea. Over two years, we monitored plant phenology, VOC emissions, NE communities on CPs, and NEs occurring within aphid colonies. The four species showed marked functional divergence and strong seasonal and interannual variability. These differences resulted in contrasting NE attractivity and, in some cases, differences in aphid colony dynamics. Overall, investigating CP functional traits and their seasonal dynamics appear essential to optimise their use as ecological infrastructures in apple orchards.