Methyl chavicol treatments of <i>Brassica rapa</i> enhance the performance of both the aphid <i>Myzus persicae</i> and its parasitoid <i>Aphidius gifuensis</i>

Aphids pose a significant threat to crop production, highlighting the need for sustainable pest management strategies. Plant-derived compounds are well-known as eco-friendly alternatives to synthetic pesticides. However, the role of methyl chavicol (MC), a phenylpropanoid found in several plant species, in inducing plant defence through exogenous application remains unexplored, despite its demonstrated insecticidal properties against various pests on direct exposure. This study aims to investigate the impact of exogenous MC applications on <i>Brassica</i> assessing performance and behaviour of <i>Myzus persicae</i> Sulzer (Aphididae) and its parasitoid <i>Aphidius gifuensis</i> Ashmead (Braconidae). Therefore, we assessed aphid survival and fecundity on MC-treated and untreated (control) plants using clip cages and evaluated behavioural responses through settlement and Y-tube olfactometer assays. Additionally, we conducted foraging and parasitism bioassays to examine performance of the natural enemy <i>A. gifuensis</i> on MC-treated plants. Our results showed that <i>M. persicae</i> exhibited higher fecundity on MC-treated plants compared to controls, indicating that MC treatment made the plants more favourable for aphid reproduction. Similarly, <i>A. gifuensis</i> demonstrated enhanced preference and parasitism behaviour towards MC-treated plants, suggesting that MC could help recruit the parasitoid. These findings suggest that MC may act as a modulator of plant defence, altering insect-plant interactions while maintaining compatibility with beneficial insects, offering a promising approach for Integrated Pest Management (IPM) programs in <i>Brassica</i> crops.