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Behavioural response of green peach aphid Myzus persicae (Sulzer) to volatiles from different rosemary (Rosmarinus officinalis L.) clones

Previous studies have shown that rosemary (Rosmarinus officinalis L.) can serve as a companion plant to control Myzus persicae (Sulzer) because of the repellent effect of certain volatile organic compounds (VOCs) that it emits. In the present study, we investigated which of five clones of rosemary may reveal a repellent effect on M. persicae and aimed to determine the possible VOCs involved. Analyses of the mixtures of VOCs released by the different clones revealed the presence of 15 main components. However, each clone was characterized by a specific volatile profile showing the existence of marked chemical variability. By testing the identified VOCs individually, using a dual‐choice olfactometer, we observed that five volatiles had a significant repulsive effect on M. persicae: bornyl acetate, camphor, α‐terpineol, terpinene‐4‐ol and geranyl acetone. In addition, only one clone of rosemary elicited a significant repulsive action. Nevertheless, all of the tested clones released compounds that are repellent to the aphid when tested individually. Therefore, the emission of individual volatiles by a rosemary plant is not sufficient to elicit a repellent effect. The concentration, proportion and even the association/synergy of VOCs in the released olfactory bouquets can probably explain these contrasting results and are worthy of additional exploration in future studies.