Effects of diversified volatile profiles on olfactory orientation of flea beetles Phyllotreta spp. and the diamondback moth Plutella xylostella

This study investigated the effect of mixing volatile organic compounds (VOC) emitted by host and non-host plants on the orientation of key pests of Brassicaceae. The study aimed to understand how these mixed VOCs influence pest behaviour, which could help in tailoring pest management strategies. The orientations of flea beetles, Phyllotreta spp., and the diamondback moth (DBM), Plutella xylostella, towards cabbage VOCs mixed with faba bean VOCs were assessed using Y-tube olfactometry. The pests' preferences were measured to determine if the presence of faba bean alongside cabbage altered their olfactory orientation compared to cabbage alone. Flea beetles showed a preference for cabbage VOCs alone over the cabbage–faba bean VOC mix. For DBM, no significant preference was observed between cabbage alone and the cabbage–faba bean mix. Previous findings indicated that faba bean attracts DBM, and in this study the mixture of cabbage and faba bean appeared to be more attractive than cabbage alone. The results indicate that faba bean VOCs can deter flea beetles from cabbage, potentially offering a pest management strategy. However, the effect on DBM was inconclusive, with no clear preference observed. This suggests that while faba bean VOCs may influence pest orientation, their effectiveness varies among different pest species. Additionally, herbivore damage to cabbage leaves did not appear to influence the odour-guided orientation of either pest, irrespective of the presence or absence of faba bean.