Effect of intercropping apple trees with basil (Ocimum basilicum) or French marigold (Tagetes patula) on the rosy apple aphid regulation (Dysaphis plantaginea) and the abundance of its natural enemies.

Background: In a global context of pesticide reduction, the sustainable management of aphids is a major challenge in maintaining economically viable fruit production. Intercropping with companion plants (CPs) that emit volatile organic compounds (VOCs) with repellent or attractive properties could be successful in the laboratory. Still, their effects on the orchard have been little documented. We tested in 2018 and 2019 the hypotheses that the introduction of basil or French marigold, decreases the populations of Dysaphis plantaginea Passerini, the rosy apple aphid (RAA) and increases the abundance of its natural enemies (NEs) in an apple orchard in the south of France.

Results: Laboratory tests confirmed that both CPs altered RAA reproduction performance. In orchards, they attracted more NEs around the pots and at some dates in the aphid colonies near the pots in both years (apart from basil in 2019), without a significant reduction in aphid populations in 2018. In contrast, in 2019, the number and spatial expansion of aphid colonies were significantly lower, close to basil.

Conclusion: Further investigation is needed to disentangle the mechanisms explaining the observed effects (e.g., repellent action in autumn, etc.) but the results highlight the potential of CPs to control aphids in orchards and contribute to agroecological production of apple. Thus, this study shows the potential of CPs in a strategy combining aphid repellency and NEs attraction to control aphids in orchards, provided that CP installation lasts over several consecutive years. © 2024 Society of Chemical Industry.