Repellence of Myzus persicae (Sulzer): evidence of two modes of action of volatiles from selected living aromatic plants.

BACKGROUND Intercropping companion plants (CPs) with horticultural crops could be an eco‐friendly strategy to optimize pest management. In this research, volatile organic compounds (VOCs) emitted by some CPs were investigated for their repellent properties towards the green peach aphid (Myzus persicae Sulzer). The aim of this study was to understand the modes of action involved: direct effects on the aphid and/or indirect effects via the host plant (pepper, Capsicum annuum L.). RESULTS We identified two promising repellent CPs species: the volatile blend from basil (Ocimum basilicum, direct repellent effect) and the mixture of (or previously intercropped) C. annuum plants with Tagetes patula cv. Nana (indirect effect). This effect was cultivar‐dependent and linked to the volatile bouquet. For the 16 compounds present in the O. basilicum or T. patula bouquets tested individually, (E)‐β‐farnesene and eugenol reported good repellent properties against M. persicae. Other compounds were repellent at medium and/or at highest concentrations. Thus, the presence of repellent VOCs in a mixture does not mean that it had a repellent propriety. CONCLUSION We identified two promising repellent CPs species towards M. persicae, with a likely effect of one CPs' VOCs on the host plant repellency and highlighted the specific effectiveness of VOC blends