Phytochemical-Mediated Tritrophic Interactions: Effects of Pepper and Eggplant Cultivars on the Green Peach Aphid Myzus persicae (Sulzer) and Its Predators

The diverse phytochemical profiles of host plants can significantly influence their interactions with herbivores and natural enemies. This study investigated the 'bottom-up' effects of several bell pepper and eggplant cultivars on the development, reproduction, and survival of the green peach aphid, <i>Myzus persicae</i> (Sulzer) (Hemiptera: Aphididae), and its predators, <i>Aphidoletes aphidimyza</i> (Rondani) (Diptera: Cecidomyiidae) and <i>Chrysoperla carnea</i> (Stephens) (Neuroptera: Chrysopidae). We analyzed the leaves of each cultivar for levels of total flavonoids, phenols, anthocyanins, and key defensive enzymes. The eggplant cultivar 'Longo' exhibited the highest concentration of secondary metabolites. Aphid populations reared on this cultivar's leaves showed a slower growth rate compared to those on other cultivars. Conversely, predators fed on these aphids demonstrated higher rates of population growth and produced more offspring. Accordingly, the intrinsic rate of natural increase (<i>r</i>) was lower for aphids feeding on 'Longo', but significantly higher for both <i>A. aphidimyza</i> and <i>C. carnea</i> when fed those aphids. These results demonstrate that elevated secondary metabolites on 'Longo' suppress the performance of <i>M. persicae</i> while enhancing predator efficiency, thereby providing a phytochemical-based approach that can serve as an effective component of integrated pest management (IPM) programs.